Evolutionary trends and patterns in centipedesegment number based on a cladistic analysis ofMecistocephalidae (Chilopoda: Geophilomorpha)
LUC IO BONATO , DONATELLA FODDAI andALESSANDRO MINELL IDepartment of Biology, University of Padova, Padova, Italy
Abstract. Evolutionary changes in segment number during the radiation ofMecistocephalidae, a group of geophilomorph centipedes with segment numberusually invariant at the species level, were explored based on a cladistic analysis offorty-six mecistocephalid species, representative of the extant diversity in segmentnumber. The data matrix included 118 morphological characters. Trends wererecognized in the evolution of segment number and discussed in relation to theunderlying ontogenetic mechanisms of segmentation. The basic trend was towardsan increasingly higher number of leg-bearing segments, from (most probably)forty-one to sixty-five (101 in one exceptional case). Changes always involvedeven sets of segments. Additions of two, four or eight segments usually occurred,but a case of overall duplication of the whole number was also documented. Mostchanges occurred starting from values belonging to the arithmetical series forty-one, forty-five, forty-nine, whereas the intermediate values forty-three, forty-seven, fifty-one were often evolutionary dead-ends. This evidence suggests amultiplicative mechanism of segmentation involving one or more final run ofduplication, as well as a precise control of the final number of segments whichproduces absolute number stability, except for a single, highly derived species withan exceptionally high number of segments. These ideas contribute to a moregeneral model of arthropod segmentation recently developed by Minelli. A taxo-nomic revision of mecistocephalids is presented: three subfamilies are proposed(Arrupinae, Dicellophilinae and Mecistocephalinae) and Sundarrup is recognizedas a junior synonym of Anarrup.
Introduction
Phylogenetics vs developmental genetics in the study of
centipede segmentation
The origin and evolution of segmentation features as one
of the most fashionable topics in evolutionary developmental
biology (Gerhart & Kirschner, 1997; Hall, 1998; Wolpert,
1998; Carroll et al., 2000). Fundamental contributions have
been provided by the study of the embryonic pattern of
expression of the so-called segmentation genes. A wealth
of data has been gathered, in particular, for Drosophila,
where a dozen segmentation genes have been characterized
in terms of nucleotide sequence and of spatial and temporal
patterns of expression. Since the emergence of this new
awareness of the complexity of the genetic control of seg-
mentation processes in the fruitfly embryo, a major problem
emerged, i.e. to what extent segmentation in Drosophila can
be safely regarded as representative of segmentation in
insects, or in arthropods at large. More recently, a sequence
of putative orthologues of Drosophila segmentation genes
was obtained from a variety of metazoans and the embryonic
expression patterns of some of these genes were described in
other arthropods and in nonarthropod metazoans. With the
progress in the knowledge of these and other genes involved
in establishing basic features of body architecture, however,
it became increasingly clear that the presence of conserved
Correspondence: Alessandro Minelli, Department of Biology,
University of Padova, via U. Bassi 58B, I-35131 Padova, Italy.
E-mail: [email protected]
Systematic Entomology (2003) 28, 539–579
# 2003 The Royal Entomological Society 539
orthologues of these genes does not guarantee, per se, the
conservation of their expression patterns. Furthermore, the
conservation of their expression pattern does not guarantee
the conservation of the role of these genes in the specification
or patterning of body features, due to possible changes in
the control cascades of which these genes are part. This may
be due, in particular, to changes in promoter sequences.
These circumstances cause difficulties in generalizing from
one or a few model systems to a whole phylum or, still
worse, to interphylum comparisons. This explains the
disparity of opinions recently expressed as to the origin
and evolution of segmentation in metazoans. On the one
hand, the presence of orthologues of Drosophila segmenta-
tion genes in nonarthropod animals, including vertebrates,
and the similarities in the pattern of expression of at least
one of these genes between arthropods and vertebrates, has
been used to support the concept of a very ancient origin of
segmentation, in the so-called Urbilateria, the putative
ancestor of all triploblastic animals (Kimmel, 1996;
Balavoine, 1997; DeRobertis, 1997; Holland et al., 1997).
On the other hand, the differences between arthropods and
annelids in the way segmentation is achieved have been
construed as proof that these two clades evolved segmenta-
tion independently from one another (Minelli & Bortoletto,
1988; Conway Morris, 1994; Valentine, 1994, 1995; Budd,
1996; Minelli, 1998, 2000), thus bringing fundamental
support to the dismantling of the traditional concept of
Articulata, a superphylum of segmented protostomes,
mainly ArthropodaþAnnelida, a view also supported by
molecular evidence (Eernisse et al., 1992; Aguinaldo et al.,
1997; Eernisse, 1997; Giribet et al., 2000).
We believe that it is now time to study evolutionary
developmental problems, such as the origin and evolution
of segmentation, using an integrated approach, where the
new evidence stemming from developmental genetics and
molecular biology of a few model animals is supplemented
by a comparative study of those groups where the trait we
are interested in (in this case, segmentation) exhibits an
extensive pattern of variation.
From this point of view, myriapods and, especially,
centipedes offer a unique opportunity among extant
arthropods. The diversity of intra- and interspecific vari-
ation in segment number, coupled with the diversity of post-
embryonic schedules in the expression of the final
complement of trunk segments, is obviously attractive as a
potential source of information about the way arthropod
segmentation may have evolved. No fewer than three
research groups are currently working on myriapod devel-
opmental genetics, but the results are still too fragmentary
to be used in a comparative context. Unfortunately, due to
their very long life cycle and to many aspects of their
reproductive biology, including the obligate parental care
provided by scolopendromorph and geophilomorph centi-
pedes and some millipedes to their broods, no millipede or
centipede species seems likely to become a convenient model
animal for experimental study like Drosophila, Schistocerca
and Artemia.
On the other hand, an extensive dataset is available on
the diversity and variation of trunk segment number in
millipedes and centipedes. In this paper, we demonstrate
that plotting these data on to a cladistic analysis of the
relevant taxa may provide a valuable contribution to the
study of evolutionary trends in arthropod segmentation.
The group focused on in this study wasMecistocephalidae.
The reasons for this choice are quite obvious, in the light
of the phylogenetic position of this taxon. Morphological
(Prunesco, 1967; Foddai, 1998; Foddai & Minelli, 2000)
as well as molecular evidence (Edgecombe et al., 1999;
Giribet et al., 1999; Edgecombe & Giribet, 2002) agree
in placing mecistocephalids in a basal position within the
geophilomorph centipedes (Fig. 1). This is reflected in two
features of their segmentation, both of them of crucial
Scutigeromorpha Craterostigmomorpha
Lithobiomorpha
Scolopendromorpha Adesmata
MecistocephalidaeDevonobiomorpha
Fig. 1. Phylogenetic relationships of the major centipede groups [according to Dohle (1985), Shear & Bonamo (1988), Borucki (1996),
Edgecombe et al. (1999, 2000), Giribet et al. (1999, 2001), Foddai & Minelli (2000), Kraus (2001) and Edgecombe & Giribet (2002)]. For a
different view, however, see Shultz & Regier (1997) and Regier & Shultz (2001). Habitus figures modified after Manton (1965), Shear &
Bonamo (1988) and Shinohara (1999).
540 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
importance in the context of this paper. On the one hand,
the number of leg-bearing segments is invariant within
each species (but see below for an exception) and identical
in the two sexes, as it is in the most basal centipede clades
(scutigeromorphs, lithobiomorphs, craterostigmomorphs,
scolopendromorphs), whereas in all species of higher
geophilomorphs (Adesmata) there is a more or less large
amount of intraspecific variability in the number of trunk
segments and the females have a segment number higher
than the conspecific males. On the other hand, the number
of leg-bearing segments in mecistocephalids (forty-one to
101) is much higher than in the more basal centipedes
(fifteen in scutigeromorphs, lithobiomorphs and cratero-
stigmomorphs, twenty-one or twenty-three in scolopendro-
morphs) and well in the range of the other geophilomorphs
(twenty-seven to 191); still more relevant, the number is
different in different species.
The regular spacing of the most frequent segment numbers
in this family (forty-one, forty-five and forty-nine) has
already been remarked upon (Minelli & Bortoletto, 1988)
and is obviously suggestive of numerical constraints deriving
from the very mechanism of segmentation. Many questions,
however, have never been addressed before. First, which is
the plesiomorphic segment number within mecistocepha-
lids? Second, whether this clade exhibits a consistent trend
towards higher (or lower) segment numbers or not. Third,
whether the evolutionary changes which occurred in the
segment number followed some regularity or not. Finally,
the recent discovery (Bonato et al., 2001) that the mecisto-
cephalid species with the highest number of trunk segments
shows an intraspecific variability in this character, at variance
with all other species in the family, prompted us to
investigate the phyletic position of this unique species
within mecistocephalids. We tried to address these questions
by reading the evolution of the segment number upon a
phylogeny of mecistocephalids to recognize possible trends,
constraints and patterns.
Centipede segmentation: pattern and process
The view of centipede segmentation providing the back-
ground to our analysis of mecistocephalids is the double
segmentation model first suggested by Maynard Smith
(1960) and subsequently developed, with special regard to
the centipedes, by Minelli & Bortoletto (1988), Minelli
(2000, 2001) and Minelli et al. (2000). Mecistocephalids
are quite typical of the apparently counterintuitive behav-
iour observed by Maynard Smith, of animals with a very
high number of serial elements (here, trunk segments) not
showing any evidence of intraspecific variability. It seems
improbable, indeed, that these elements are serially gener-
ated from a growth zone by an error-free process. A lack of
intraspecific variability, instead, could be expected if these
serial elements were produced in two steps: first, production
of a small number of first-order units; second, subdivision
of each first-order unit into a fixed number of second-order
units. According to Minelli (2001), the trunk segments of a
centipede (including the forcipular segment, the leg-bearing
segments and the terminal segments) possibly originates
through the secondary subdivision of nine primary units.
The number of primary units is supposed to be the same in
all centipedes, the different centipede clades differing
instead in the number of secondary units derived from
each primary unit (e.g. two from each primary unit in
lithobiomorphs, three from most primary units in scolopen-
dromorphs, four from most primary units in geophilo-
morphs with thirty-one pairs of legs). In this context, a
comparison with the expression patterns of the pair-rule
genes in Drosophila (Lawrence, 1992; Carroll et al., 2000)
is interesting in that a first seven-stripe expression is
followed by a secondary fourteen-stripe expression, with
sets of two secondary stripes corresponding, more or less
closely, to each primary stripe. It is therefore possible that a
‘double segmentation’ mechanism represents a generalized
feature of arthropod segmentation (Minelli, 2001).
Mecistocephalidae
Within geophilomorph centipedes, Mecistocephalidae is
a monophyletic basal clade well characterized by several
peculiar morphological features of the cephalic capsule,
the mouthparts, the forcipular segment and the trunk
sterna. In all mecistocephalids, the number of segments
does not increase during the postembryonic development:
the centipede hatches with the full complement of segments
because segmentation is completed during the embryonic
life.
Mecistocephalids are characterized by the intraspecific
invariance in segment number, a plesiomorphic trait which
is lost in the other geophilomorphs, i.e. Adesmata (see
Minelli & Bortoletto, 1988). A single case of intraspecific
variability in segment number recently found in Mecistoce-
phalus microporus (see Bonato et al., 2001), does not detract
from the phylogenetic relevance of this trait.
Different species are characterized by different numbers
of segments. Fifteen different numbers are known: almost
all the odd numbers from forty-one to sixty-five (except for
fifty-five and sixty-one) and the odd numbers from ninety-
three to 101 (except for ninety-nine).
The taxonomy of the family has not been revised since
Attems’s (1929) standard account, which is by now largely
unsatisfactory. Taxonomic work on this group has mostly
overlooked the standardization of morphological descrip-
tions and the checking of the diagnostic value of traditional
characters, particularly with respect to developmental
changes and intraspecific variability. Useful exceptions are
three of Crabill’s papers (Crabill, 1959, 1964, 1970), whose
contribution, however, has been substantially ignored by
subsequent authors.
About 170 mecistocephalid species in a dozen genera are
currently recognized. Most of the species are included in the
large genus Mecistocephalus, especially in the nominotypical
subgenus.
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Materials and methods
A cladistic analysis of the whole group of mecistocephalids
was performed. The monophyly of this group is supported
by reliable synapomorphies (see below under Taxonomic
implications and Appendix 3). As operational units, species
were preferred to taxa belonging to higher taxonomic levels.
Data were thus collected referring to individual species
rather than to hypothetical ancestors, according to the
exemplar approach (Yeates, 1995; Prendini, 2001).
Ingroup
Forty-six species of mecistocephalids were considered
(Table 1), representatives of the morphological diversity
and the geographical distribution of the group, as well as
all different numbers of segments on record. Species belong-
ing to all current genera and subgenera were included,
except for the following minor taxa, too incompletely
known and for which no specimens were available: Fusichila
Chamberlin (monotypic), Mecistocephalus (Ectoptyx)
Chamberlin (five species), Megalacrus Attems (monotypic),
Partygarrupius Verhoeff (monotypic). As far as possible,
type species were preferred over other species. For Agno-
strup Foddai, Bonato, Pereira & Minelli, Mecistocephalus
(Dasyptyx) Chamberlin, Mecistocephalus (Pauroptyx)
Chamberlin and Tygarrup Chamberlin, for which
the type species are too poorly known, other species were
chosen.
Outgroup
Outgroup species were chosen on the basis of the phylo-
genetic scenario most generally accepted for the centipedes
(Fig. 1). Two species were selected from Adesmata, one
from Scolopendromorpha, one from Lithobiomorpha
(Table 1). Adesmata are very diverse and most of them are
characterized by specialized traits, thus they could be mis-
leading as outgroup taxa. Scolopendromorphs appear more
homogeneous and conservative in morphological features;
however, the anatomy of their forcipular segment is highly
derived and some similarities between geophilomorphs and
cryptopid scolopendromorphs may be due to convergent
adaptation to underground life. The extinct devono-
biomorphs were not considered because their morphology
is only partially known. Craterostigmomorphs were not
included because some derivative characters, the anogenital
capsule in particular, are hard to interpret comparatively.
Lithobiomorphs, instead, seemed to be very suitable as an
outgroup, because their anatomy is very close to the
hypothetical ground-plan of the centipedes (Dohle, 1985;
Borucki, 1996).
In the analysis, only the lithobiomorph species was used
to root the trees. The other species were not bound.
Characters
In total, 118 characters were considered, referring to
morphological and anatomical features (Appendix 1).
Characters representing autapomorphies of single species
were excluded.
To define the characters properly, preliminary investiga-
tions were performed on large series of specimens belonging
to representative species. All characters were checked for
their stability during postembryonic development, for
sexual dimorphism and for interindividual variability.
Characters traditionally used in the taxonomy of this
group were checked for their diagnostic value. Additional
characters were recognized as informative and, thus,
considered in the analysis.
Collection of data
As far as possible, series of adult specimens, both males
and females, were studied for each species. All four out-
group species and thirty-one of the forty-six ingroup species
could be studied directly (Table 1). For the remaining
species, data were collected from the primary literature.
For light microscopy investigations, specimens were
clarified with a lactophenol solution and mounted on
temporary glass slides. For some specimens, dissection of
the mouthparts was needed. Standard anatomical parts
were drawn for each species, by means of a camera lucida.
Phylogenetic analysis
Two different analyses were performed, one considering
only those characters not referring to the number of seg-
ments (116 characters, chs 1–116 in Appendix 1), the other
considering all the 118 characters. By excluding the char-
acters which we wanted to optimize a posteriori, the first
analysis allowed us to avoid any possibility of circular
reasoning (see, e.g. Brooks & McLennan, 1991). Conver-
sely, the second analysis allowed us to exploit completely all
potentially informative data to infer phylogeny, not exclud-
ing any character a priori (see, e.g. Miller & Wenzel, 1995).
The inclusive data matrix is shown in Appendix 2. Binary
coding was applied as far as possible. When multistate
coding was required, the different states were treated as
unordered. All characters were originally equally weighted.
PAUP* 4.0 b10 (Swofford, 2002) was used to find the most
parsimonious trees by means of heuristic search. The search
strategy actually consisted of 1000 replicates of a stepwise
addition procedure with random sequence, followed by tree
bisection and reconnection (TBR) branch swapping of a
maximum of ten trees (PAUP* command: HSearch
AddSeq¼ random NReps¼ 1000Hold¼ 10). Both AccTran
and DelTran character optimization methods were
performed. An iterative procedure of successive weighting
and search was then applied (Farris, 1969): at each subse-
quent run, each character was re-weighted according to its
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# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Table 1. Species considered in the analysis. Within Mecistocephalidae, species are entered with their current name and are listed in
alphabetical order. For each species, the number of leg-bearing segments (n) and the overall distribution are given. Species which are types in
their genera are marked with an asterisk.
Species n Distribution Direct study
Lithobiomorpha
Lithobius forficatus (Linnaeus, 1758) 15 Europe, Mediterranean Basin þScolopendromorpha
Cryptops anomalans Newport, 1844 21 Europe, Mediterranean Basin þAdesmata
Geophilus insculptus Attems, 1895 43–47 Europe þStigmatogaster gracilis Meinert, 1870 83–111 Mediterranean Basin þ
Mecistocephalidae
Agnostrup paucipes (Miyosi, 1955) 41 Hondo –
Anarrup nesiotes Chamberlin, 1920* 41 Sulawesi –
Arrup dentatus (Takakuwa, 1934) 41 Hokkaido þArrup holstii (Pocock, 1895) 41 Eastern Asia þArrup pylorus Chamberlin, 1912* 41 California –
Dicellophilus anomalus (Chamberlin, 1904) 41 California þDicellophilus carniolensis (C. L. Koch, 1847) 43 Central Europe þDicellophilus latifrons Takakuwa, 1934 41 Hondo þDicellophilus limatus (Wood, 1862)* 45 California þKrateraspis meinerti (Sseliwanoff, 1881)* 45 Central Asia –
Krateraspis sselivanovi Titova, 1975 53 Central Asia –
Mecistocephalus (Mecistocephalus) angusticeps (Ribaut, 1914) 47 Eastern Africa –
Mecistocephalus benoiti Dobroruka, 1958 49 Eastern Africa þMecistocephalus (Mecistocephalus) conspicuus Attems, 1938 49 Indochinese Peninsula, Java –
Mecistocephalus (Mecistocephalus) diversisternus (Silvestri, 1919) 57 Hondo, Hainan þMecistocephalus (Mecistocephalus) guildingii Newport, 1843 49 Central America –
Mecistocephalus (Mecistocephalus) itayai Takakuwa, 1939 49 Caroline Islands –
Mecistocephalus japonicus Meinert, 1886 63 Hondo, Taiwan þMecistocephalus (Mecistocephalus) lifuensis Pocock, 1899 51 New Caledonia, Loyalty Islands –
Mecistocephalus longiceps Lawrence, 1960 49 Madagascar –
Mecistocephalus (Formosocephalus) longichilatus Takakuwa, 1936 49 Taiwan –
Mecistocephalus microporus Haase, 1887 93–101 Philippines þMecistocephalus (Mecistocephalus) mikado Attems, 1928 49 Eastern Asia þMecistocephalus (Brachyptyx) mirandus Pocock, 1895 65 Hondo, Taiwan þMecistocephalus (Mecistocephalus) modestus (Silvestri, 1919) 49 Southeastern Asia þMecistocephalus (Mecistocephalus) multidentatus Takakuwa, 1936 49 Hondo, Taiwan þMecistocephalus (Mecistocephalus) nannocornis Chamberlin, 1920 45 Southeastern Asia þMecistocephalus (Mecistocephalus) punctifrons Newport, 1843* 49 Indian Peninsula þMecistocephalus (Mecistocephalus) spissus Wood, 1862 45 Hawaii þMecistocephalus (Dasyptyx) subgigas (Silvestri, 1919) 49 New Guinea þMecistocephalus (Pauroptyx) superior (Silvestri, 1919) 49 Indian Peninsula –
Mecistocephalus (Mecistocephalus) tahitiensis Wood, 1862 47 Southeastern Asia, Oceania þMecistocephalus (Mecistocephalus) takakuwai Verhoeff, 1934 59 Hondo, Taiwan þMecistocephalus sp. A 47 Marquesas Islands þMecistocephalus sp. B 51 Sulawesi þMecistocephalus sp. C 53 Hainan þNannarrup hoffmani Foddai, Bonato, Pereira & Minelli, 2003* 41 Unknown þProterotaiwanella sculptulata (Takakuwa, 1936) 49 Taiwan –
Proterotaiwanella tanabei Bonato, Foddai & Minelli, 2002* 45 Ryukyu Islands þSundarrup flavipes Attems, 1930* 41 Lesser Sunda þTakashimaia ramungula Miyosi, 1955* 45 Hondo þTygarrup anepipe Verhoeff, 1939 45 Mascarene Islands –
Tygarrup javanicus Attems, 1929 45 Southeastern Asia þTygarrup muminabadicus Titova, 1965 45 Himalayas þTygarrup takarazimensis Miyosi, 1957 45 Tokara Islands þTygarrup sp. A 43 Andaman Islands þ
Evolution of segment number in Mecistocephalidae 543
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
maximum rescaled consistency index (CI), which was calcu-
lated on the trees obtained during the preceding run (PAUP*
command: Reweight); at each run, a search was performed
according to the same strategy as the first one.
A bootstrap analysis was performed to evaluate the
statistical support of the clades: subsequent to the applica-
tion of the character weights obtained by the iterative
procedure described above, 100 resamplings of characters
were performed, with an equal probability among charac-
ters; for each resampling, 100 replicates of the original
heuristic procedure were performed (PAUP* command:
Bootstrap NReps¼ 100 Wts¼ simple / AddSeq¼ random
NReps¼ 100 Hold¼ 10).
The evolution of the number of leg-bearing segments in
mecistocephalids was then analysed by optimizing this char-
acter (ch. 118 in Appendix 1) on the phylogenetic trees,
according to a parsimony assumption (PAUP* command:
Reconstruct 118). Both AccTran and DelTran character
optimization methods were performed.
Results and discussion
Phylogeny of Mecistocephalidae
The analysis performed on the 116 characters not refer-
ring to the number of segments, produced one most parsi-
monious tree [109.25 steps after successive weighting; CI
(excluding uninformative characters)¼ 0.55; retention
index (RI)¼ 0.85; Fig. 2], whereas the analysis performed
on all 118 characters produced three equally most parsimo-
nious trees [120.99 steps after successive weighting; CI
(excluding uninformative characters)¼ 0.57; RI¼ 0.85;
Fig. 3]. The same trees were obtained using both AccTran
and DelTran character optimization methods.
The trees differ only for minor details. The three trees
obtained from the second analysis differ in the position of
Mecistocephalus modestus, which emerges close to Mecisto-
cephalus longichilatus in all the trees. Apart from this, these
trees differ from the tree obtained from the first analysis in
the position ofMecistocephalus lifuensis, a species with fifty-
one leg-bearing segments, which emerges either within a
Mecistocephalus group with forty-nine segments or as sister
species of another species with fifty-one segments.
In all trees obtained, the scolopendromorph Cryptops
anomalans is basal to all geophilomorphs, following the
fixed outgroup Lithobius forficatus. The two representatives
of the adesmate geophilomorphs, i.e. Stigmatogaster gracilis
and Geophilus insculptus, branch together and opposite to
all mecistocephalids. This is in full agreement with the
currently recognized phyletic assessment of the major
groups of centipedes (Dohle, 1985; Borucki, 1996;
Edgecombe et al., 1999, 2000; Giribet et al., 1999, 2001;
Foddai & Minelli, 2000; Kraus, 2001; Edgecombe &
Giribet, 2002; Fig. 1).
The monophyletic condition of mecistocephalids is con-
firmed and strongly supported in all trees. The internal
topology of the group is nearly resolved and many, but
not all, nodes are supported by reliable synapomorphies
(see Appendix 3) and high bootstrap values.
For some characters both analyses suggest some evolu-
tionary trends. In particular, the head becomes more and
more elongate, as already hypothesized by Crabill (1970)
without the support of an adequate phylogenetic analysis.
The elongation involves the cephalic plate, buccae and
maxillary coxosterna (ch. 50), but not the clypeus, labrum
or mandibles. The ratio of the length to the width of the
cephalic plate is as low as 1.2–1.4 in some Arrup and Dicel-
lophilus, 1.4–1.5 in other close genera, 1.7 in Tygarrup,
Takashimaia, Krateraspis and the basal Mecistocephalus,
and reaches even higher values, up to 2.1, in some derived
species of Mecistocephalus.
A clear trend also marks the evolution of the forcipular
segment: the tergum becomes increasingly narrow (ch. 74),
so that the pleura are broadly visible from above; the tro-
chanteropraefemur becomes relatively longer and narrower
(chs 86 and 87) and its proximal tooth becomes evident
(ch. 88). A primitive condition is retained in Arrup and
other related genera, whereas the most derived condition
is seen in some Mecistocephalus.
A clear trend also appears in the evolution of the cerrus
(chs 84 and 85). Whereas the cerrus is completely lacking in
Arrup and other basal genera, a pair of lateral groups of
setae is present in Dicellophilus, in other related genera and
in some basal Mecistocephalus. In some derived Mecistoce-
phalus, two additional paramedian rows of setae are also
developed. A peculiar pattern is found in Mecistocephalus
punctifrons and a few other species, where the rows are
enlarged in bands coalescent with the lateral groups.
The position of the metameric pores, the direction of the
grooves starting from these pores and the relative elonga-
tion of the foraminal processes probably underwent parallel
evolution in different mecistocephalid clades (ch. 69).
Crabill (1964) speculated on a trend towards a lateral
displacement of the metameric pores, a lateral opening of
the groove and a reduction of the foraminal process, in
relation to the elongation of the whole head. Our phylo-
genetic analysis confirms this hypothesis in part only.
Taxonomic implications
On the basis of this cladistic analysis, as well as a critical
evaluation of current taxonomy, a revised phylogenetic sys-
tem of Mecistocephalidae is proposed (Table 2). Recent
taxonomic contributions on Proterotaiwanella and Arrupi-
nae (Bonato et al., 2002; Foddai et al., 2003) are included.
The taxonomic arrangement and nomenclature introduced
in those papers are adopted in the following discussion.
We recognize three subfamilies, fundamentally corres-
ponding to three main well-supported clades within the
mecistocephalids but only partially equivalent to the trad-
itional subfamilies. These three taxa are Arrupinae, Dicello-
philinae and Mecistocephalinae (see below).
Sundarrup Attems, 1930 is recognized as a junior synonym
ofAnarrup Chamberlin, 1920 (syn.n.). The original diagnoses
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of these two nominal genera are overlapping and their type
species, Sundarrup flavipes Attems, 1930 and Anarrup
nesiotes Chamberlin, 1920, respectively, are sister species in
our phylogenetic analyses. Worth noticing is that Sundarrup
and Anarrup were previously placed in two different subfam-
ilies, Mecistocephalinae and Arrupinae, respectively.
The internal phylogeny of Mecistocephalus does not sup-
port the current partition of the genus into subgenera.
Lithobius forficatus
Cryptops anomalans
Stigmatogaster gracilis
Geophilus insculptus
Arrup pylorus
Arrup dentatus
Arrup holstiiNannarrup hoffmani
Agnostrup paucipes
Dicellophilus limatus
Dicellophilus anomalus
Dicellophilus latifrons
Dicellophilus carniolensis
Anarrup nesiotes
Sundarrup flavipes
Proterotaiwanella sculptulata
Tygarrup anepipe
Tygarrup javanicus
Tygarrup muminabadicus
Tygarrup takarazimensis
Krateraspis meinerti
Krateraspis sselivanovi
Takashimaia ramungula
Mecistocephalus M. spissus( )
Mecistocephalus benoiti
Mecistocephalus M. nannocornis( )
Mecistocephalus M. angusticeps( )
Mecistocephalus M. tahitiensis( )
Mecistocephalus F. longichilatus( )
Mecistocephalus M. modestus( )
Mecistocephalus M. conspicuus( )
Mecistocephalus M. lifuensis( )
Mecistocephalus M. guildingii( )
Mecistocephalus longiceps
Mecistocephalus M. itayai( )
Mecistocephalus M. diversisternus( )
Mecistocephalus M. takakuwai( )
Mecistocephalus japonicus
Mecistocephalus M. multidentatus
Mecistocephalus M. punctifrons( )
( )
Mecistocephalus M. mikado( )
Mecistocephalus P. superior( )
Mecistocephalus D. subgigas( )
Mecistocephalus microporus
Mecistocephalus B. mirandus( )
Mecistocephalus sp. A
Mecistocephalus sp. B
Mecistocephalus sp. C
Proterotaiwanella tanabei
Tygarrup sp. A
5251
50
49
42
4140
39
3837
36
35
34
31
30
29
2624
23
22
21
11
13
16
8
3
7
6
5
15
12
10
14
20
1918
17
9
2
1
4
2528
27
4846
43
47
6353
41
59
10058
98
8431
20
10
36
29
17
39
37
3577
92
63
44
86
98
90
61
79
82
74
77
98
84
41
100
3032
62
27
39
99
100
100
9623
26
3669
27
21
Fig. 2. The most parsimonious phylogenetic tree obtained from the cladistic analysis excluding characters related to the number of segments
[116 characters; 109.25 steps after successive weighting; consistency index (CI; excluding uninformative characters)¼ 0.55; retention index
(RI)¼ 0.85]. For each node, a conventional number (above) and the bootstrap value (below) are indicated. Species are entered with their
current names (Table 1).
Evolution of segment number in Mecistocephalidae 545
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Whereas Brachyptyx Chamberlin, 1920, Pauroptyx
Chamberlin, 1920, Dasyptyx Chamberlin, 1920, Ectoptyx
Chamberlin, 1920 and Formosocephalus Verhoeff, 1937
are probably monophyletic, the nominotypical subgenus
Mecistocephalus Newport, 1843 is clearly paraphyletic. The
present arrangement is thus not satisfactory, but we cannot
yet confidently suggest an alternative one. For the moment,
we propose to ignore the traditional subgenera within
Mecistocephalus. In the same vein, we have already proposed
to abandon Megethmus Cook, 1896, a nominal genus intro-
duced for Mecistocephalus microporus, which clearly falls
within the radiation ofMecistocephalus (Bonato et al., 2001).
Fusichila waipaheenas Chamberlin, 1953 and Megalacrus
obscuratus Attems, 1953 are provisionally maintained with
Lithobius forficatus
Cryptops anomalans
Stigmatogaster gracilis
Geophilus insculptus
Arrup pylorus
Arrup dentatus
Arrup holstii
Nannarrup hoffmani
Agnostrup paucipes
Dicellophilus limatus
Dicellophilus anomalus
Dicellophilus latifrons
Dicellophilus carniolensis
Anarrup nesiotes
Sundarrup flavipes
Proterotaiwanella sculptulata
Tygarrup anepipe
Tygarrup javanicus
Tygarrup muminabadicus
Tygarrup takarazimensis
Krateraspis meinerti
Krateraspis sselivanovi
Takashimaia ramungula
Mecistocephalus (M.) spissus
Mecistocephalus benoiti
Mecistocephalus (M.) nannocornis
Mecistocephalus (M.) angusticeps
Mecistocephalus (M.) tahitiensis
Mecistocephalus (F.) longichilatus
Mecistocephalus (M.) modestus
Mecistocephalus (M.) conspicuus
Mecistocephalus (M.) lifuensi
Mecistocephalus (M.) guildingii
Mecistocephalus longiceps
Mecistocephalus (M.) itayai
Mecistocephalus (M.) diversisternus
Mecistocephalus (M.) takakuwai
Mecistocephalus japonicus
Mecistocephalus (M.) multidentatus
Mecistocephalus (M.) punctifrons
Mecistocephalus (M.) mikado
Mecistocephalus (P.) superior
Mecistocephalus (D.) subgigas
Mecistocephalus microporus
Mecistocephalus (B.) mirandus
Mecistocephalus sp. A
Mecistocephalus sp. B
Mecistocephalus sp. C
Proterotaiwanella tanabei
Tygarrup sp. A
5251
50
4948
47
46
45
4241
40
3938
37
29
26
23
21
11
13
12
1415
16
67
8
3
5
10
2019
18
28
34
31
30
27
25
24
22
17
9
4
2
1
35
44
6646
28
6034
17
56
48
9760
96
82
29
35
56
41
93
44
86
100
87
9892
84
8089
61
86
86
30
3940
64
47
29
11
41
49
99
71
59
28
43
100
100
100
33
21
A
Fig. 3. Most parsimonious phylogenetic trees (A, B, C) obtained from the cladistic analysis including characters related to the number of
segments [118 characters; 120.99 steps after successive weighting; consistency index (CI; excluding uninformative characters)¼ 0.57; retention
index (RI)¼ 0.85]. For each node, a conventional number (above) and the bootstrap value (below) are indicated. Species are entered with their
current names (Table 1).
546 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
their current names, although their taxonomic status needs
to be clarified. Both species were insufficiently described
to determine their actual relationships to other mecistoce-
phalids.
Mecistocephalidae Bollman, 1893
Synapomorphies. Anterior part of clypeus and buccae
areolate, posterior part virtually not areolate; internal
margin of each bucca thickened into a stilus; each labrum
side-piece divided into alae by a transverse thickened line;
sterna of anterior part of trunk provided with apodemes
and mid-longitudinal sulci.
Diagnosis. Body slightly depressed, uniformly wide in its
anterior three quarters but tapering backwards. Adult body
length from c. 2 to 14 cm. Colour from pale yellow to
red-brown, head and forcipular segment darker. Antennae
2–3� longer than head, distally attenuated. Antennal setae
increasing in density from basal article to tip of appendage.
Cephalic plate subrectangular (length to width ratio 1.2–2.1),
frontal line usually present. Clypeus subdivided into an
anterior areolate part and a posterior part which is
virtually not areolate (plagula/ae). Buccae areolate in the
anterior part only, internal margin thickened (stilus). Labrum
composed of a mid-piece and 2 side-pieces, each side-piece
divided by a transverse thickened line into an anterior and
posterior ala. Paralabial sclerites not recognizable. Mandible
only provided with a series of pectinate lamellae. First
lamella similar to other lamellae but smaller, last lamellae
rudimentary. Mandibular basal tooth conical. Coxal pro-
jection of first maxillae similar in shape and extension to the
corresponding telopodite, both of them being uniarticulate
and composed of a sclerotized base and a hyaline distal
part, without any additional lobe. Coxosternum of second
maxillae usually undivided, areolate in the median part and
always provided with a pair of metameric pores. Telopodite
Mecistocephalus benoiti
Mecistocephalus (F.) longichilatus
Mecistocephalus (M.) modestus
Mecistocephalus (M.) conspicuus
Mecistocephalus (M.) lifuensis
Mecistocephalus (M.) guildingii
Mecistocephalus longiceps
Mecistocephalus (M.) itayai
Mecistocephalus (M.) diversisternus
Mecistocephalus (M.) takakuwai
Mecistocephalus japonicus
Mecistocephalus (M.) multidentatus
Mecistocephalus (M.) punctifrons
Mecistocephalus (M.) mikado
Mecistocephalus (P.) superiorMecistocephalus (M.) subgigas
Mecistocephalus microporus
Mecistocephalus (B.) mirandusMecistocephalus sp. B
Mecistocephalus sp. C
5251
50
4948
47
46
45
4241
40
3938
37
34
32
30
35
44
6646
28
6034
17
56
48
9760
96
8229
35
29
29
41
33
21
B
Mecistocephalus benoiti
Mecistocephalus (F.) longichilatus
Mecistocephalus (M.) modestus
Mecistocephalus (M.) conspicuus
Mecistocephalus (M.) lifuensis
Mecistocephalus (M.) guildingii
Mecistocephalus longiceps
Mecistocephalus (M.) itayai
Mecistocephalus (M.) diversisternus
Mecistocephalus (M.) takakuwai
Mecistocephalus japonicus
Mecistocephalus (M.) multidentatus
Mecistocephalus (M.) punctifrons
Mecistocephalus (M.) mikado
Mecistocephalus (P.) superior
Mecistocephalus (D.) subgigas
Mecistocephalus microporus
Mecistocephalus (B.) mirandus
Mecistocephalus sp. B
Mecistocephalus sp. C
5251
50
4948
47
46
45
4241
40
3938
37
34
35
44
6646
28
6034
17
56
48
9760
96
82
29
35
29
33
21
3041
3324
C
Fig. 3. Continued.
Table 2. Revised taxonomic system of Mecistocephalidae, based on the phylogenetic analysis presented here (see Taxonomic implications;
also Bonato et al., 2001, 2002; Foddai et al., 2003). The enigmatic Megalacrus and Fusichila, both marked with an asterisk, are provisionally
conserved as valid genera, but their taxonomic status requires further study.
Family Subfamily Genus Species
Mecistocephalidae Arrupinae Chamberlin, 1912 Agnostrup Foddai, Bonato, Pereira & Minelli, 2003 3
Bollman, 1893 Nannarrup Foddai, Bonato, Pereira & Minelli, 2003 1
Arrup Chamberlin, 1912 11
Partygarrupius Verhoeff, 1939 1
Dicellophilinae Cook, 1896 Proterotaiwanella Bonato, Foddai & Minelli, 2002 2
Anarrup Chamberlin, 1920 2
Dicellophilus Cook, 1896 4
Mecistocephalinae Bollman, 1893 Tygarrup Chamberlin, 1914 15
Krateraspis Lignau, 1929 2
Takashimaia Miyosi, 1955 1
Mecistocephalus Newport, 1843 130þ*Megalacrus Attems, 1953 1
*Fusichila Chamberlin, 1953 1
Evolution of segment number in Mecistocephalidae 547
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
of second maxillae triarticulate, usually provided with a
reduced claw. Forcipular tergum narrower than cephalic
plate, partially covered by the latter and by tergum of first
leg-bearing segment. Forcipular pleura widely visible from
above, each provided with a dorsal setigerous ridge and
ending anteriorly in a pointed scapula. Forcipular coxoster-
num wider than cephalic plate, its antero-external parts
visible from above. A pair of tiny teeth on anterior margin
of forcipular coxosternum. No chitin-lines. Forcipular
telopodites rather large, clearly visible from above beyond
lateral margins of cephalic plate, usually also in front of
same. Forcipular tarsungulum relatively long. Forcipular
trochanteropraefemur with a distal, sometimes also a
proximal tooth; intermediate articles often with a tooth
each. Poison calyx elongate, usually reaching distal part of
trochanteropraefemur. Terga of leg-bearing trunk with 2
paramedian sulci, fading in most posterior segments. Sterna
of leg-bearing trunk with an internal apodema and a mid-
longitudinal sulcus, fading in posterior segments. Anterior
sterna with a posterior endosternal process, gradually
reduced in size in posterior segments. First pair of legs
shorter than following pairs. Tergum and sternum of last
leg-bearing segment rather elongate. Coxopleura covered
by 10s of circular pores. Telopodite of last legs of 6 articles,
thin (although sometimes slightly swollen in males)
and longer than telopodite of remaining legs. Praetarsus of
last leg extremely reduced. Posterior part of last sternum
and ventral internal margins of coxopleura covered by
dense pilosity. Gonopods biarticulate. Anal pores usually
present.
Nomenclature. Bollman (1893) introduced the name
Mecistocephalinae as a subfamily of Geophilidae to group
all the mecistocephalid species hitherto known. The name
was first used for a family by Verhoeff in 1908 (Verhoeff,
1902–1925).
Arrupinae Chamberlin, 1912
Type genus. Arrup Chamberlin, 1912.
Included genera. Arrup Chamberlin, 1912 (¼ Prolam-
nonyx Silvestri, 1919; Nodocephalus Attems, 1928) (eleven
species); Partygarrupius Verhoeff, 1939 (one species);
Agnostrup Foddai, Bonato, Pereira & Minelli, 2003 (three
species); Nannarrup Foddai, Bonato, Pereira & Minelli,
2003 (one species).
Remarks on monophyly. The clade composed by Arrup,
Agnostrup and Nannarrup is well supported by both reliable
synapomorphies and good bootstrap values. Partygarrupius
was not sufficiently known to be included in this analysis,
but some morphological features suggest it is most closely
related to the former genera than to other basal mecisto-
cephalids, as also suggested by a more restricted phylogenetic
analysis (Foddai et al., 2003).
Synapomorphies. Telopodites of second maxillae quite
short, not overreaching those of first maxillae.
Diagnosis. Body inconspicuously tapering backwards.
Leg-bearing trunk uniform in colour, without dark patches.
Cephalic plate only slightly longer than wide. Usually 2
clypeal plagulae divided by a mid-longitudinal stripe, not
covering more than posterior half of clypeus. Clypeal setae
a few to 10s, mainly placed in 2 lateral quite long areas.
Buccae without setae. Spiculum absent. Internal margin of
labral anterior ala reduced to a pointed end. Posterior alae
without longitudinal stripes. Posterior margin of labral side-
piece sinuous, not fringed. Coxosternum of first maxillae
either divided and nonareolate or undivided and areolate;
anterolateral corners virtually absent. Coxosternum of sec-
ond maxillae undivided or coxae connected by a membran-
ous isthmus. Groove from metameric pore and foraminal
process reaching postero-external corner of coxosternum.
Telopodites of second maxillae not overreaching those of
first maxillae. Forcipular tergum evidently wider than long,
without a mid-longitudinal sulcus. Cerrus absent. Forci-
pular trochanteropraefemur stout, with a distal tooth only.
Sternal mid-longitudinal sulci not furcate. Number of pairs
of legs 41. Sternum of last leg-bearing segment without a
pillowlike process.
Distribution. Eastern Asia from Hokkaido to Taiwan
(Partygarrupius, Agnostrup and Arrup), central Asia
(Arrup), California (Arrup). The true homeland of
Nannarrup, whose only species was described on specimens
collected in New York (U.S.A.), is unknown.
Nomenclature. Chamberlin (1912) introduced the name
Arrupidae for the single genus Arrup, later shifting the name
to subfamily level under Mecistocephalidae (Chamberlin,
1920a). Attems (1929) followed this arrangement, which
was later critically discussed only by Crabill (1964). The
delimitation proposed herewith is different from all
previous ones in the inclusion of Partygarrupius and the
exclusion of Anarrup.
Dicellophilinae Cook, 1896
Type genus. Dicellophilus Cook, 1896.
Included genera. Dicellophilus Cook, 1896 (four species);
Anarrup Chamberlin, 1920 (¼Sundarrup Attems, 1930)
(two species); Proterotaiwanella Bonato, Foddai & Minelli,
2002 (two species).
Remarks on monophyly. The clade comprising Dicello-
philus and Anarrup is well supported by both reliable syna-
pomorphies and good bootstrap values. Proterotaiwanella is
basal to this clade in all the trees and some reliable synapo-
morphies support this position, despite low bootstrap
values.
548 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Synapomorphies. A spinous tubercle on tip of last pair
of legs.
Diagnosis. Body evidently tapering backwards. Leg-
bearing trunk uniform in colour, without dark patches.
Cephalic plate evidently longer than wide. Usually an entire
clypeal plagula, covering more than posterior half of
clypeus. Tens of clypeal setae. Spiculum absent. Internal
margin of labral anterior ala reduced to a pointed end;
posterior alae with notches or longitudinal stripes. Coxo-
sternum of first maxillae divided, nonareolate; anterolateral
corners usually absent. Coxosternum of second maxillae
either undivided or divided by a mid-longitudinal suture.
Groove from metameric pore and foraminal process reach-
ing either postero-external corner or lateral margin of
coxosternum. Telopodites of second maxillae usually well
developed and overreaching those of first maxillae, terminal
article often swollen and homogeneously covered with
setae. Forcipular tergum slightly wider than long, with a
mid-longitudinal sulcus. Cerrus composed of 2 lateral
groups of setae only. Forcipular trochanteropraefemur quite
stout, with a distal tooth only. Sternal mid-longitudinal
sulci not furcate. Number of pairs of legs 41, 43, 45 or
49. Sternum of last leg-bearing segment with a pillowlike
process. Legs of last pair with several additional short setae
and a tuberclelike praetarsus covered with tiny spines.
Distribution. Eastern Asia from Hondo to Malay Archi-
pelago (Dicellophilus, Proterotaiwanella, Anarrup), central
Europe (Dicellophilus), California (Dicellophilus).
Nomenclature. The name was originally proposed by
Cook (1896) as family Dicellophilidae, to include all the
mecistocephalid species described to that time. Hence,
equivalent to Mecistocephalidae Bollman, 1893. Cook did
not base the family group name on Mecistocephalus New-
port, 1843 because he designated as type of this genus the
geophilid Geophilus attenuatus Say, 1821, a nominal species
he regarded as a senior synonym of Geophilus ferrugineus
C.L. Koch, 1835, which is currently ascribed to Pachymer-
ium in family Geophilidae. As a consequence, Cook
regarded Mecistocephalus as not belonging to the family
under discussion and proposed three new generic names,
Dicellophilus, Lamnonyx and Megethmus, to include the
mecistocephalid species known to his date. This matter
was clarified by Crabill (1957). The name Dicellophilinae
is used here in a more restricted sense.
Mecistocephalinae Bollman, 1893
Type genus. Mecistocephalus Newport, 1843.
Included genera. Mecistocephalus Newport, 1843
(¼ LamnonyxCook, 1896;MegethmusCook, 1896. Including
also: Brachyptyx Chamberlin, 1920; Dasyptyx Chamberlin,
1920; Ectoptyx Chamberlin, 1920; Pauroptyx Chamberlin,
1920; Formosocephalus Verhoeff, 1937) (c. 130 species);
Tygarrup Chamberlin, 1914 (¼ Brahmaputrus Verhoeff,
1942) (fifteen species); Krateraspis Lignau, 1929 (two
species); Takashimaia Miyosi, 1955 (one species). Addition-
ally, Megalacrus Attems, 1953 (one species) and Fusichila
Chamberlin, 1953 (one species) are provisionally assigned to
this subfamily.
Remarks on monophyly. The clade composed by Krater-
aspis, Takashimaia and Mecistocephalus is well supported
by both reliable synapomorphies and good bootstrap
values. Tygarrup is basal to this clade in all our trees and
some reliable synapomorphies support this position, despite
low bootstrap values.
Synapomorphies. Clypeal setae limited to a short trans-
verse band; thickened transverse line of labrum side-piece
straight.
Diagnosis. Body evidently tapering backwards. Leg-
bearing trunk often provided with dark patches. Cephalic
plate evidently longer than wide. Clypeal plagula/ae cover-
ing more than posterior half of clypeus. Clypeal setae
usually a few, limited to a short transverse band and to
anterolateral corners. Posterior alae without longitudinal
stripes. Posterior margin of labrum sinuous. Coxosternum
of first maxillae divided, nonareolate. Coxosternum of sec-
ond maxillae undivided, medial part areolate; groove from
metameric pore and foraminal process reaching lateral mar-
gin. Telopodites of second maxillae well developed, over-
reaching those of first maxillae; terminal article usually
covered with setae, mainly on internal side, and bearing a
reduced claw. Forcipular tergum slightly wider than long,
with a mid-longitudinal sulcus. Forcipular trochanteroprae-
femur usually elongate, sometimes provided with a proxi-
mal tooth. Sternal mid-longitudinal sulci either furcate or
not. Number of pairs of legs 45, 47, 49, 51, 53, 57, 59, 63 or
65; in only one species, odd numbers between 93 and 101.
Sternum of last leg-bearing segment often with a pillowlike
process. Legs of last pair usually provided with an apical
spine.
Distribution. Mainly tropical regions, in particular
Southeast Asia, but also eastern Asia, Pacific islands,
Australia, Indian Peninsula, Africa and the Americas.
Nomenclature. Chamberlin (1920a) was the first to
distinguish two subfamilies within Mecistocephalidae, thus
reserving the name Mecistocephalinae for the nominotyp-
ical subfamily. Here we use Mecistocephalinae in a more
restricted sense.
Evolution of segment numbers
Optimizing the number of leg-bearing segments (ch. 118)
on the phylogenetic trees, we could estimate the most prob-
able number at each node, under a parsimony hypothesis
(Figs 4, 5). Analyses with both AccTran and DelTran
Evolution of segment number in Mecistocephalidae 549
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
optimization methods were performed, but the DelTran
option generated some clearly unreliable hypotheses
(e.g. fifteen leg-bearing segments at the base of the
mecistocephalids; cf. e.g. Minelli et al., 2000) and thus
was not considered further.
Following AccTran optimization, the number of
leg-bearing segments of the common ancestor of mecisto-
cephalids was probably forty-one, which is also the
most common number in both Arrupinae and Dicello-
philinae. In Arrupinae, the ancestral number was strictly
conserved in all species, irrespective of the overall morpho-
logical diversity in this subfamily. In Dicellophilinae,
conversely, relevant changes occurred, in particular in
Dicellophilus (from forty-one to forty-three and, indepen-
dently, from forty-one to forty-five) and in Proterotaiwa-
nella (from forty-five to forty-nine). In Mecistocephalinae,
the basal number forty-five changed independently to
forty-three in Tygarrup and to fifty-three in Krateraspis.
Changes from forty-five to either forty-seven or forty-nine
happened at the base of Mecistocephalus, but the topology
is too weakly supported to recognize them unambiguously.
Some further changes from forty-nine to higher numbers
occurred within different derived groups of Mecisto-
cephalus.
Lithobius forficatus
Cryptops anomalans
Stigmatogaster gracilis
Geophilus insculptusArrup pylorusArrup dentatus
Arrup holstii
Nannarrup hoffmani
Agnostrup paucipes
Dicellophilus limatusDicellophilus anomalusDicellophilus latifrons
Dicellophilus carniolensisAnarrup nesiotes
Anarrup flavipes
Proterotaiwanella sculptulata
Tygarrup anepipe
Tygarrup javanicus
Tygarrup muminabadicus
Tygarrup takarazimensis
Krateraspis meinertiKrateraspis sselivanovi
Takashimaia ramungula
Mecistocephalus spissus
Mecistocephalus benoiti
Mecistocephalus nannocornis
Mecistocephalus angusticeps
Mecistocephalus tahitiensis
Mecistocephalus longichilatus
Mecistocephalus modestus
Mecistocephalus conspicuus
Mecistocephalus lifuensis
Mecistocephalus guildingiiMecistocephalus longicepsMecistocephalus itayai
Mecistocephalus diversisternus
Mecistocephalus takakuwai
Mecistocephalus japonicus
Mecistocephalus multidentatus
Mecistocephalus punctifronsMecistocephalus mikado
Mecistocephalus superiorMecistocephalus subgigas
Mecistocephalus microporus
Mecistocephalus mirandus
Mecistocephalus sp. A
Mecistocephalus sp. B
Mecistocephalus sp. C
Proterotaiwanella tanabei
Tygarrup sp. A
41
45
45
45
45
45
47
49
49
49
49
49
4949
49
4949
6359
5749
4949
49
49 49
49
49
49
49
53
49
51
6563
59
57
494949
51
4949
49
47474745
45
45
5345
4545
45
45
4549
4141
43
41
4541
4141
41
4143 – 4783 – 111
21
15
41
43
93 – 101
49
45
45
4545
4545
45
41
41
41
45
4141
4141
4141
?
4747
?
+4
+2
+2
+4
+ 2+ 2
+2
+2
+8
– 2
–4
+ 4
+2
+4
+8
+4
×2
?
Fig. 4. Evolution of the number of trunk segments in mecistocephalids, based on the AccTran optimization of the number of leg-bearing
segments (ch. 118) on the most parsimonious tree obtained excluding characters related to this number (Fig. 2). For each species, the number
of leg-bearing segments is reported. For each node, the hypothetical ancestral number is reported below the node. The number of segments
probably added or lost is indicated above the branches. Species names follow the revised taxonomy presented here.
550 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Increases by two, four or eight segments most often
occurred in the evolution of mecistocephalids. Two-segment
increases most probably happened with the origin of
Dicellophilus carniolensis (from forty-one to forty-three),
with the differentiation of a basal group of Mecistocephalus
species (from forty-five to forty-seven) and in the radiation
of the most derived Mecistocephalus (for instance from
forty-nine to fifty-one). The analysis of characters not
related with segmentation suggested that this latter change
happened twice independently, whereas the analysis of all
characters suggested that it happened only once. Although
the apparent additions of more than two segments could be
due to the iterated additions of two segments, direct four-
segment increases most probably occurred with the origin of
Proterotaiwanella sculptulata (from forty-five to forty-nine),
in the differentiation ofDicellophilus limatus (from forty-one
Mecistocephalus angusticeps
Lithobius forficatus
Cryptops anomalans
Arrup pylorus
Arrup dentatus
Arrup holstii
Nannarrup hoffmani
Agnostrup paucipes
Dicellophilus limatus
Dicellophilus anomalus
Dicellophilus latifrons
Dicellophilus carniolensis
Anarrup nesiotes
Anarrup flavipes
Proterotaiwanella sculptulata
Tygarrup anepipe
Tygarrup javanicus
Tygarrup muminabadicus
Tygarrup takarazimensis
Krateraspis meinerti
Krateraspis sselivanovi
Takashimaia ramungula
Mecistocephalus spissus
Mecistocephalus benoiti
Mecistocephalus nannocornis
Mecistocephalus tahitiensis
Mecistocephalus longichilatus
Mecistocephalus modestus
Mecistocephalus conspicuus
Mecistocephalus lifuensis
Mecistocephalus guildingii
Mecistocephalus longiceps
Mecistocephalus itayai
Mecistocephalus diversisternus
Mecistocephalus takakuwai
Mecistocephalus japonicus
Mecistocephalus multidentatus
Mecistocephalus punctifrons
Mecistocephalus mikado
Mecistocephalus superior
Mecistocephalus subgigas
Mecistocephalus mirandus
Mecistocephalus sp. A
Mecistocephalus sp. B
Mecistocephalus sp. C
Proterotaiwanella tanabei
Tygarrup sp. A
41
4141
41
?
45
41
41
41
45
4141
–4
+4
+2
+4
45
45
45
4545
+8
–2
45
4747
6359
57
49
49
49
+2
+8
+4
49
49
49
49
4949
4949
+4
+2
×2
41
45
45
45
45
45
47
49
49
49
49
?
+4
+2
+2
?
41
41
43
41
45
41
4141
41
41
43–47 Geophilus insculptus
83–111 Stigmatogaster gracilis
21
15
41
49
47
47
47
45
45
45
53
45
45
45
45
45
45
49
43
49
53
49
51
51
65
63
59
57
49
49
49
49
49
93–101 Mecistocephalus microporus
49
49
49
49
+2
51
A
Fig. 5. Evolution of the number of trunk segments in mecistocephalids, based on the AccTran optimization of the number of leg-bearing
segments (ch. 118) on the three most parsimonious trees (A, B, C) obtained including characters related to this number (Fig. 3). For each
species, the number of leg-bearing segments is reported. For each node, the hypothetical ancestral number is reported below the node. The
number of segments probably added or lost is indicated above the branches. Species names follow the revised taxonomy presented here.
Evolution of segment number in Mecistocephalidae 551
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
to forty-five) and within the radiation of the most
derived Mecistocephalus (from forty-nine to fifty-three). In
the same way, eight-segment increases most probably
occurred at the origin of Krateraspis sselivanovi (from
forty-five to fifty-three) at least. Additions of six segments,
conversely, seem never to have occurred, as suggested by
both AccTran and DelTran optimization. The same seems
true for additions of more than eight segments, except for
the anomalous case of Mecistocephalus microporus (see
below). Transitions internal to the Mecistocephalus group
with fifty-seven to sixty-five leg-bearing segments are hard
to determine confidently, but additions of two, four and
eight segments may fully explain the observed values.
Evolutionary decreases of segment number seem to have
occurred only rarely. The best supported case is a two-segment
decrease at the origin of aTygarrup species (from forty-five to
forty-three segments). A transition from forty-five to forty-
one segments at the base of Dicellophilinae is more dubious.
A peculiar transition occurred with the origin of Mecis-
tocephalus microporus, characterized by a variable number
of ninety-three to 101 leg-bearing segments, from a group of
Mecistocephalus species with an invariant number of forty-
nine. Such a dramatic transition appears as a direct overall
duplication of the original number of segments (see also
Bonato et al., 2001).
As a result, the evolution of mecistocephalids followed a
general trend towards higher numbers of segments: the
addition of two, four or eight segments occurred often, as
well as one overall duplication of the total number of seg-
ments (or something like that). Conversely, a decrease in
segment number was a rare occurrence and involved low
numbers of segments only (probably, just two).
The very derived position of Mecistocephalus microporus
within Mecistocephalus and, by implication, within the
whole family, shows that the intraspecific variability in the
number of segments evolved at least twice in geophilo-
morph centipedes, i.e. in this species and in the common
ancestor of Adesmata. It is also possible that some addi-
tional, albeit less conspicuous, case of intraspecific variation
in segment number is present in other mecistocephalid spe-
cies, but was overlooked because of preconceived views on
segment stability in this group.
Biogeography and segment numbers
Most mecistocephalid species occur in tropical and sub-
tropical regions (Fig. 6). The group is widespread from the
Pacific islands, through southern Asia, to most of Africa
and also reaches tropical America. Some species, however,
live in temperate regions such as the Japanese Archipelago
and some restricted zones of Europe, the Asiatic mainland
and North America. Maximum morphological diversity is
recognizable in the Japanese area, more precisely in the
Hondo Archipelago. Here, the mecistocephalid fauna com-
prises some tens of species belonging to eight genera in all
three subfamilies and eight different numbers of segments
are represented. Less diverse but quite rich faunas are found
in Southeast Asia and the whole oriental region generally.
Several tens of species were described from these regions
and many other species still await description.
A detailed biogeographical analysis was outside the aims
of this work. Nevertheless, the geographical distribution of
the main mecistocephalid groups was revised and the occur-
rence of different numbers of segments throughout the
world was analysed (Fig. 6). Some biogeographical evidence
suggests evolutionary patterns broadly consistent with the
phylogenetic hypotheses obtained from the morphological
analysis, thus bringing further support to them.
In Arrupinae, Dicellophilinae and basal Mecistocephali-
nae (Tygarrup, Krateraspis and Takashimaia), most species
ranges are quite restricted and separate, suggesting a vicar-
iance pattern. Conversely, in the most derived group, i.e.
Mecistocephalus, the ranges are significantly wider and
often overlapping, suggesting dispersal patterns.
Dicellophilus is characterized by a relatively low morpho-
logical diversity (four species, very similar to each other),
contrasting with their diversity in segment number (three
Mecistocephalus benoiti
Mecistocephalus longichilatus
Mecistocephalus modestus
Mecistocephalus conspicuus
Mecistocephalus lifuensis
Mecistocephalus guildingii
Mecistocephalus longiceps
Mecistocephalus itayai
Mecistocephalus diversisternus
Mecistocephalus takakuwai
Mecistocephalus japonicus
Mecistocephalus multidentatus
Mecistocephalus punctifrons
Mecistocephalus mikado
Mecistocephalus superiorMecistocephalus subgigas
Mecistocephalus mirandusMecistocephalus sp. B
Mecistocephalus sp. C
49
53
93–101 Mecistocephalus microporus
49
49
49
49
49
51
5165
63
59
57
49
4949
49
4949
49
49
49
49
4949
49
5759
49
49
4949
49
4949
51
63
×2
+4
+2
+8+2
+4
49
+2
B
Mecistocephalus modestus
Mecistocephalus benoiti
Mecistocephalus longichilatus
Mecistocephalus conspicuus
Mecistocephalus lifuensis
Mecistocephalus guildingii
Mecistocephalus longiceps
Mecistocephalus itayai
Mecistocephalus diversisternus
Mecistocephalus takakuwai
Mecistocephalus japonicus
Mecistocephalus multidentatus
Mecistocephalus punctifrons
Mecistocephalus mikado
Mecistocephalus superior
Mecistocephalus subgigas
Mecistocephalus mirandus
Mecistocephalus sp. B
Mecistocephalus sp. C
49
53
93–101 Mecistocephalus microporus
49
49
49
4949
49
4949
4949
+4
×2
49
51
51
65
63
59
57
49
49
49
49
4949
49
49
49
49
+251
6359
57
4949
49
+4+2
+2
49
49
+8
C
Fig. 5. Continued.
552 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
different values). The genus is limited to temperate
regions and shows a strongly disjoint distribution, each
species living in a quite restricted range: D. carniolensis
occurs in central Europe (eastern Alps, Dinarids and
Carpathians), D. latifrons in Honshu, D. anomalus and
D. limatus in California. All these features indicate the
relic condition of this group and agree with the phylogeny
in suggesting a consistent biogeographical history: the
two Californian species are sister species and more
closely related to the Japanese species than to the European
one.
Anarrup and Dicellophilus were reliably resolved as sister
groups, but their contrasting distribution (tropical vs tem-
perate) is a bit puzzling and possibly relic. The phylogeny of
Tygarrup, although supported by low bootstrap values,
suggests a consistent evolutionary trend in geographical
colonization and ecological adaptation. The basal Tygarrup
species, i.e. T. takarazimensis and most probably the related
T. quelpartensis, live on some minor islands south of Hondo
(Tokara and Quelpart Islands, respectively), within the
range of the most basal mecistocephalid groups, very far
from the other Tygarrup species and north of all of them.
B
Mec 49Mec 51
Mec 51
Mec 51
Mec 47
Mec 57
Mec 59Mec 63Mec 65
Mec 47Mec 57
Mec 49
C
Mec 93–101Mec 45
Mec 45
Mec 47
Mec 45
Mec 53Mec 57
Arr 41
Arr 41Dic 43
Agn 41 Dic 41Dic 41Dic 45
Arr 41Par 41
A
Nan 41
Tyg 45
Tak 45
Pro 45
Ana 41
Kra 45Kra 53
Tyg 43
Tyg 45
Pro 49
Fig. 6. Distribution of the mecistocephalid genera, according to the revised taxonomic system proposed in this paper. Separate ranges are
drawn for different numbers of segments. The first three letters of the generic name are followed by the number of leg-bearing segments in the
species belonging to the same genus. A, Partygarrupius, Agnostrup, Nannarrup, Arrup and Dicellophilus; B, Proterotaiwanella, Anarrup,
Tygarrup, Krateraspis and Takashimaia; C, Mecistocephalus.
Evolution of segment number in Mecistocephalidae 553
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Both species are characterized by medium size (adults are
25–30mm long) and are evidently adapted to temperate
climates. Tygarrup muminabadicus is representative of a
first group of species which emerged from the basal Tygar-
rup. These species live on the mountains of south-central
Asia, from the Indochinese mountains to the Himalayas.
These species are apparently adapted to cold alpine climates
(up to 4000m a.s.l) and are characterized by larger size
(adults are often 40–50mm long). The most derived group
of Tygarrup species is composed of T. javanicus, T. anepipe,
an undescribed species with forty-three leg-bearing seg-
ments and most probably some other related species. All
these species live on tropical islands, usually at low altitude,
in particular on some large Indonesian islands (Java,
Sumatra, Halmahera) and on some small archipelagos in
the Indian Ocean (Andaman, Seychelles and Mascarene
Islands). They are all characterized by very small size
(adults at most 20mm long). Thus, the evolutionary history
of Tygarrup was probably characterized by a progressive
colonization of southern regions, from Japan to the south-
ern continental Asia, then through Indochina to the Great
Sunda Islands and finally to the Indian Ocean archipelagos
by sea dispersal.
Mecistocephalus occupies a very large geographical
range. Maximum diversity, in terms of species as well as
segment numbers, is in the Japanese region and Southeast
Asia. A gradual decrease can be observed along the tropical
regions both eastwards, through the Pacific islands, and
westwards, through the Indian Ocean to Africa and
America. Eastwards, different species with forty-seven,
forty-nine or fifty-one leg-bearing segments are found on
the Melanesian islands; fewer species with either forty-seven
or forty-nine segments are found on the archipelagos of the
central Pacific; on Clipperton Island, facing the American
coast, only one species with forty-nine segments is present.
Westwards, different species with forty-seven, forty-nine
and fifty-one segments (possibly also fifty-seven) inhabit
the Seychelles and Mascarene Islands; fewer species exist
in Africa and Madagascar, most of them with forty-nine
segments but also one species with forty-seven segments is
recorded; only one species (or a very small number of
closely related species) with forty-nine segments is found
in America.
Mecistocephalus species with fifty-one leg-bearing
segments occur within the overall range of those with
forty-nine segments, but with a discontinuous distribution,
mainly from Sulawesi through the Melanesian islands to the
Fiji Islands. There are some records also from the Seychelles
and the Middle East. This pattern agrees with the hypoth-
esis that Mecistocephalus species with fifty-one leg-bearing
segments originated from species with forty-nine segments,
but at different occasions and places, as suggested by our
cladistic analysiswhere segmentation characterswere excluded.
Mecistocephalus species with fifty-seven, fifty-nine, sixty-
three and sixty-five leg-bearing segments show quite coin-
cident distributions, well within the overall range of the
congeneric species with forty-nine segments: all four num-
bers were recorded from Hondo and all but fifty-seven from
Taiwan. These biogeographical elements support the mono-
phyly of this species group and its evolution from a Mecis-
tocephalus with forty-nine segments.
Mecistocephalus microporus, characterized by a high and
variable number of leg-bearing segments (ninety-three to
101), is only known from two major islands of the Philip-
pines (Bonato et al., 2001). The presence of this species on a
young archipelago, close to the centre of specific diversity of
the Mecistocephalus with forty-nine pairs of legs, confirms
its relatively recent origin from an ancestor with forty-nine
pairs of legs, as suggested by the phylogenetic analysis.
Segmentation: evolution and development
The phylogenetic analysis of mecistocephalids revealed
interesting trends and patterns in the evolution of the seg-
mental arrangement of these centipedes. Some of them have
been suggested by previous comparative studies (see Intro-
duction), others are new and somehow unexpected.
Evolutionary changes always involved an even number of
segments. In the evolution of the mecistocephalids, the
number of segments changed sixteen times at least. At
each event, the difference between the plesiomorphic and
the derived number was an even number, usually two, four
or eight. As a consequence, the number of leg-bearing seg-
ments remained invariantly odd. This confirms the well-
known rule, common to all the centipedes, according to
which only odd numbers of leg-bearing segments are pre-
sent in the adult (Minelli & Bortoletto, 1988; Arthur &
Farrow, 1999; Minelli et al., 2000). This rule suggests a
very strong developmental constraint. The minimum struc-
tural unit in both development and evolution is thus a pair
of contiguous segments rather than a single segment. This is
also suggested by a bulk of other evidence from previous
investigations on centipedes, as well as on other arthropods,
by means of comparative morphology and developmental
genetics, e.g. the invariably odd pairs of legs in all centi-
pedes, the diplosegments in millipedes and the pair-rule
genes in Drosophila.
Evolutionary changes usually implied an increase in the
number of segments. The evolutionary history of mecisto-
cephalids was characterized by a trend towards an increas-
ingly higher number of segments, from a putative original
number of forty-one leg-bearing segments to sixty-five and
in one exceptional case to 101. Number increases occurred
often, whereas only very few instances of decrease have
been detected. Moreover, additions sometimes involved
large sets of segments (up to eight, but also c. fifty segments
in the exceptional case of Mecistocephalus microporus),
whereas decreases were always by no more than four seg-
ments. The same trend is clear in the evolution of the
centipedes as a whole (Minelli et al., 2000): the ancestral
number of fifteen leg-bearing segments (conserved in scuti-
geromorphs, lithobiomorphs and craterostigmomorphs)
increased both in scolopendromorphs (probably to
554 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
twenty-one and then to twenty-three) and in geophilo-
morphs (to a basal unknown value). Within the geophilo-
morphs, the number increased further many times, up to
191, whereas it decreased less often and less conspicuously,
down to twenty-seven in a few Adesmata (Minelli et al.,
2000). The same general trend has been recognized in the
evolution of millipedes. The hypothetical ancestor of the
diplopods probably had seventeen pairs of legs and the
ancestor of the chilognathans c. thirty-six pairs (Enghoff,
1990; Enghoff et al., 1993). The extant millipedes, instead,
have from fourteen to more than 300 pairs. This trend,
common to most lineages of myriapods, evidently refutes
a previously fashionable hypothesis on the evolution of
segmented bodies: according to this hypothesis (known as
Williston’s rule), primitive multisegmented and little pat-
terned organisms evolved into shorter and more extensively
patterned forms (for a critical discussion, see Dohle, 1985;
Berto et al., 1997; Fusco & Minelli, 2000a; Minelli et al.,
2000).
Evolutionary changes involved a number of segments
apparently belonging to the geometrical series two, four,
eight. Whereas the addition of two, four and eight segments
surely happened many times during the evolutionary his-
tory of mecistocephalids, no case of the addition of six
segments is suggested by the phylogenetic analysis. This
rule is mirrored by the patterns recognizable in the fre-
quency distributions of the number of segments in other
centipedes. Comparing the species within each geophilo-
morph family, the most frequent numbers usually differ by
four, eight or sixteen segments (Minelli & Bortoletto, 1988).
Comparing individuals of the geophilomorph Himantarium
gabrielis, the most frequent numbers differ by sixteen seg-
ments (Minelli et al., 1984). Within Adesmata, the number
of additional segments found in females compared with
conspecific males are often two, four, eight or sixteen
(Minelli & Bortoletto, 1988; Minelli, 2000; Minelli et al.,
2000). A highly probable developmental constraint thus
emerges. It could be explained by admitting that at least
three runs of overall duplication of a small number of
primary trunk segments occur in the late stages of segmen-
tation. Under this hypothesis, a developmental fault produ-
cing one additional segment just before one of these runs
could determine, as a final outcome, an addition of two,
four or eight segments, depending on the stage affected by
the fault. This hypothesis is consistent with the recent model
of segmentation proposed by Minelli (2000, 2001) and
briefly summarized in the Introduction: the three runs of
duplication hypothesized here could be considered as the
last part of the hierarchical pattern of the secondary seg-
mentation of each primary segment.
Evolutionary changes most often occurred from values of
the segment number belonging to the arithmetic series forty-
one, forty-five, forty-nine. During the evolution of mecisto-
cephalids, the possible numbers of segments seem to have
followed two alternative behaviours. Lineages with forty-
one, forty-five or forty-nine leg-bearing segments under-
went abundant speciation as well as further changes in the
number of segments. Conversely, lineages with forty-three,
forty-seven or fifty-one leg-bearing segments showed a very
low evolvability, often featuring as evolutionary ‘dead
branches’, poorly able to change further and even to speci-
ate. This evidence is somehow congruent with the frequency
distribution of the number of leg-bearing segments in Ades-
mata, where the most frequent numbers are 39þ 4k, with k
an integer (Minelli, 2000). The morphogenetic processes
underlying this puzzling pattern, however, are still unclear.
One evolutionary change at least implied an overall
duplication of the total (or almost total) number of
segments. The origin of Mecistocephalus microporus was
evidently accompanied by a conspicuous increase in the
number of leg-bearing segments, to a number about double
that of the hypothetical ancestor (ninety-three to 101 vs
forty-nine). The fact that Mecistocephalus microporus is
most probably the only species of mecistocephalids that is
certainly variable in segment number could be enlightening.
We could hypothesize that an additional run of duplication,
involving all (or most) of the trunk segments, occurred
during the morphogenetic process of segmentation and
was accompanied by a loss of the precise morphogenetic
control of the definitive number of segments (Bonato et al.,
2001).
In conclusion, the phylogenetic analysis of mecistocepha-
lids contributed consistently and sometimes unexpectedly to
the evidence that the comparative re-examination of centi-
pede morphology is gathering, towards an understanding of
the evolution of the trunk structure of these animals. In
particular, the morphological patterns and constraints
shown by the present analysis are consistent with a model
of arthropod segmentation (Minelli, 2001), the predictions
of which now need to be tested experimentally.
Acknowledgements
We are sincerely grateful to numerous colleagues and
friends for the loan of specimens, and in particular to
J. Beccaloni (The Natural History Museum, London,
U.K.), P. Beron (Bulgarian Academy of Sciences, Sofia,
Bulgaria), H. W. Chang (National Sun Yat-Sen University,
Kaohsiung, Taiwan), M. Daccordi (formerly, Museo Civico
di Storia Naturale, Verona, Italy), L. Deharveng (Universite
Paul Sabatier, Toulouse, France), J. Dunlop (Museum fur
Naturkunde, Berlin, Germany), H. Enghoff (Zoologisk
Museum,Copenhagen,Denmark), C. E.Griswold (California
Academy of Science, San Francisco, California, U.S.A.),
R. L. Hoffman (Virginia Museum of Natural History,
Martinsville, Virginia, U.S.A.), K. Ishii (Dokkyo University
School of Medicine, Mibu, Tochigi, Japan), J. Ledford
(California Academy of Science, San Francisco, California,
U.S.A.), P. Lehtinen (University of Turku, Turku, Finland),
L. Leibensperger (Museum of Comparative Zoology,
Cambridge, Massachusetts, U.S.A.), J. Martens (Johannes
Gutenberg Universitat, Mainz, Germany), J. P. Mauries
Evolution of segment number in Mecistocephalidae 555
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
(Museum National d’Histoire Naturelle, Paris, France),
G. B. Osella (formerly, Museo Civico di Storia Naturale,
Verona, Italy), N. Platnick (American Museum of Natural
History, New York, U.S.A.), R. Shelley (North Carolina
State Museum of Natural Sciences, Raleigh, North Carolina
U.S.A.), A. A. Schileyko (Zoological Museum, Moscow,
Russia), T. Tanabe (Tokushima Prefectural Museum,
Hachiman-cho, Tokushima, Japan) and N. Tsurusaki
(Tottori University, Tottori, Japan). This work was sup-
ported by grants from the Italian MURST to A. M. and
from the University of Padova to L. B., and by financial
help to D. F. from the Zoological Museum, Copenhagen
(through COBICE facilities) and The Natural History
Museum, London (through Sys-Resource facilities). We
are very grateful to Wallace Arthur, Greg Edgecombe,
Henrik Enghoff and John G. E. Lewis for their sugges-
tions on a previous draft of this paper, and to Enrico
Negrisolo for his comments on the cladistic analyses.
Three referees helped us to improve the paper.
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Accepted 22 January 2003
Appendix 1. Characters used in the cladistic analysis
Characters are numbered in anteroposterior anatomical
order. Plesiomorphic states are coded as ‘0’. Apomorphic
states are usually coded as ‘1’, ‘2’, ‘3’, ‘4’, in arbitrary order,
but letters from ‘a’ to ‘o’ are used for ch. 118. Anatomical
terminology basically follows Crabill (1959, 1964, 1970).
Colour
1. Leg-bearing trunk, dark patches on the ground colour:
(0) absent; (1) present, in some individuals at least.
In mecistocephalids, the extent of dark patches on the
body surface is largely variable within a species. In some
species, however, all individuals are invariably uniform,
whereas in other species most individuals are covered with
dark patches. Similar patches also occur in some Adesmata,
but are generally absent in lithobiomorphs and scolopen-
dromorphs.
Antenna
2. Antenna, number of articles: (0) more than 14, often
variable within a species; (1) 14, invariable within a
species.
In all geophilomorphs, the antenna is invariably com-
posed of fourteen articles, without any difference related
to age or sex (Eason, 1964; Lewis, 1981). However, abnor-
mal antennae composed of fewer than fourteen articles are
quite frequent, even within mecistocephalids; this anomaly
is often unilateral (Minelli et al., 2000). In both lithobio-
morphs and scolopendromorphs, the number of antennal
articles is usually larger than fourteen (but only fourteen in
some adults of the lithobiomorph Anopsobius neozelanicus
Silvestri, 1909; see Archey, 1937). In these groups, the num-
ber may be different in individuals of the same population
and between the left and the right antennae of the same
specimen (Eason, 1964; Lewis, 1981; Minelli et al., 2000).
3. Antenna, number of articles: (0) increasing during
postembryonic development; (1) not increasing during
postembryonic development.
In all geophilomorphs, the number of antennal articles
does not increase during postembryonic life. This is also the
case in most scolopendromorphs, in which only minor
changes may occur (Minelli et al., 2000). In lithobiomorphs,
conversely, the number of articles increases with growth.
4. Antenna, intermediate articles, ratio of length to width:
(1) 1.4–3.0; (2) 0.7–1.3.
For geophilomorphs, the antennal article VII was chosen
as representative of the intermediate articles of the append-
age. The ratio of maximum length to maximum width of this
article was taken as a measure of the degree of elongation of
the intermediate part of the antenna. Within mecistocepha-
lids, ratios seem to aggregate into two main intervals, as
distinguished here. This ratio may be affected by age and sex
and is slightly variable among conspecific specimens; thus,
for each species, the ratio has been estimated as far as
possible from a series of adult females. We did not apply
this character to lithobiomorphs and scolopendromorphs
because antennal article VII in these groups is not strictly
homologous to article VII in geophilomorphs. More gener-
ally, individual elements in the series of numerous and
variable antennal articles of lithobiomorphs and
Evolution of segment number in Mecistocephalidae 559
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scolopendromorphs are difficult to homologize with those
of the series of invariably fourteen articles in geophilo-
morphs. The developmental mechanisms determining the
segmentation of centipede antennae are still unknown
(Lewis, 2000; Minelli et al., 2000).
5. Antenna, ordinary setae, size and density: (0) not
changing along the antennal axis; (1) changing gradually
along the antennal axis; (2) changing abruptly along the
antennal axis.
In geophilomorphs, the size and density of the antennal
setae change gradually along the appendage. However, in a
few species of Adesmata the distribution of setae on the
antennae is sexually dimorphic (Pereira, 1999; Pereira et al.,
2002; we have also observed a case in an undescribed species
of Mecistocephalus from New Guinea). In scolopendro-
morphs, the change is generally more abrupt than in geo-
philomorphs (Lewis, 2000). In lithobiomorphs, conversely,
the size and density of the setae are virtually homogeneous
along the antennae.
6. Antennae and last pair of legs, rows of spinelike sensilla:
(0) absent; (1) present.
The spinelike sensilla [‘sensilla microtrichoidea’ of Ernst
(1983, 1997, 2000); ‘sensilla for telescopic movements’ of
Foddai & Minelli (2000)] are conical processes, similar in
shape to the setae but relatively shorter, a few micrometres
long, articulated at the base with the cuticular surface. They
are distributed in rows (up to six sensilla in each row), close
to the arthrodial membranes between sclerites. These sen-
silla are supposed to be mechanoreceptors, involved in con-
trolling the relative position of articles of appendages and
segments (Ernst, 2000; Foddai & Minelli, 2000). In geophi-
lomorphs, rows of spinelike sensilla are always present both
on the antennal articles (in three series: dorsal, ventro-
internal and ventro-external) and on the articles of the telopo-
dites of the last pair of legs (in two series: internal and
external). These sensilla are present in all individuals, but
the number of sensilla in each row increases during growth
and shows some interindividual variability. The same pat-
tern of rows of sensilla is present in some scolopendromorphs,
whereas it is not known in lithobiomorphs. In the latter,
however, groups of spinelike sensilla, not precisely aligned,
are present on some antennal articles, at least inLithobius and
Henicopidae (Edgecombe, 2001).
7. Antenna, buttonlike sensilla: (0) present; (1) virtually
absent.
The buttonlike sensilla [‘sensilla coeloconica’ of Ernst
(1995, 2000)] are stout subconical processes, very few micro-
metres long and wide, ringed by a shallow relief. Their
sensorial function is not known. Most mecistocephalid
species are characterized by buttonlike sensilla on the anten-
nae. It is not clear whether buttonlike sensilla, or at least
different sensilla in a homologous position, occur on the
antennae of lithobiomorphs and scolopendromorphs
(Lewis, 2000). However, preliminary observations suggest
that a few sensilla of this kind also occur in Lithobius and
Cryptops. The presence of these sensilla in mecistocephalids
was largely ignored in the taxonomic literature: only a few
authors have reported their occurrence, but they often mis-
interpreted them as either glandular pores (Verhoeff, 1934,
1939; Wurmli, 1972) or punctuate depressions (Haase, 1887;
Silvestri, 1919).
8. Antenna, spearlike sensilla: (0) absent; (1) present.
The spearlike sensilla [Fig. 7; a type of ‘sensilla brachy-
conica’ of Ernst (1981, 2000)] are thin processes, usually
5–10 mm long, bearing a crown of stout processes at mid-
length which are coalescent to different degrees. They were
supposed to be thermo- and hygroreceptors (Ernst, 1981,
2000). Within mecistocephalids, a few spearlike sensilla are
usually found on the antennal tip and their presence is not
affected by either age or sex. In some species, spearlike
sensilla are apparently lacking in all individuals. Similar
sensilla are also known in many Adesmata, either limited
to the antennal tip or also occurring on other antennal
articles. Conversely, they apparently never occur in litho-
biomorphs and scolopendromorphs. Interestingly, how-
ever, apparently homologous elements are present on the
antennal tips of craterostigmomorphs, a group probably
basal to all Epimorpha (Fig. 1). Furthermore, preliminary
investigations by light and electron microscopy revealed
that the antennal tip of many lithobiomorphs bears a
group of sensilla, apparently different from the spearlike
sensilla but possibly homologous in position (personal
observations).
Cephalic plate
9. Cephalic plate, lateral margins: (0) parallel; (1) slightly
convergent backwards; (2) strongly convergent backwards.
In some mecistocephalid species, the lateral margins of
the cephalic plate are slightly and uniformly convergent
backwards (Fig. 8A), in other species the margins are sub-
parallel at head mid-length (Fig. 8D) and in a few other
species they are strongly convergent backwards (Fig. 8C).
ab
c
Fig. 7. Spearlike sensilla (a), ordinary setae (b) and clublike
sensilla (c) on the antennal tip in a representative mecistocephalid
(Tygarrup muminabadicus, /, subadult, Kashmir) (simplified
drawing after a scanning electron micrograph). Scale¼ 0.01mm.
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The lateral margins are generally subparallel in all other
geophilomorphs, more diverse in the other orders.
10. Cephalic plate, posterior margin: (0) straight;
(1) rounded.
In mecistocephalids, the posterior margin of the cephalic
plate is usually straight or truncate (Fig. 8D), but curved in
a few species (Fig. 8A). A straight posterior margin also
characterizes the head of most Adesmata, lithobiomorphs
and scolopendromorphs.
11. Cephalic plate, frontal line: (0) present; (1) absent.
A transverse frontal line occurs on the cephalic plate of
most geophilomorphs (Eason, 1964; Foddai & Minelli, 2000;
Fig. 8). A probably homologous line is present in lithobio-
morphs (see, e.g. Eason, 1964; Edgecombe et al., 1999;
Edgecombe & Giribet, 2002), but not in scolopendromorphs.
12. Cephalic plate, frontal line: (0) uniformly rounded;
(1) with a vertex pointing backwards; (2) with a vertex
pointing forwards.
This character obviously only applies to species with the
frontal line (see ch. 11). Within mecistocephalids, the
frontal line is generally uniformly rounded, the convexity
bending backwards (Fig. 8D). In some species, however, it
forms a backward directed angle (Fig. 8C), whereas in other
species it forms a forward directed angle (Fig. 8B). But the
angle is not always recognizable in all individuals of a given
species. Therefore, this character has been evaluated, when-
ever possible, on a series of conspecific individuals. In
Adesmata, scolopendromorphs and lithobiomorphs, the
frontal line is usually rounded.
13. Cephalic plate, cephalic sulci: (0) present; (1) absent.
The cephalic sulci are a pair of shallow grooves, running
longitudinally on the posterior part of the cephalic plate, in
correspondencewith the paramedian rows of setae and sensilla.
Some species of mecistocephalids have cephalic sulci, whereas
others lack them. No intraspecific variability has been noticed
for this character, but in the smallest individuals the sulci are
difficult to observe. Cephalic sulci are not recognizable in
Adesmata and scolopendromorphs. In the latter, however,
lines usually regarded as ‘sutures’ (Eason, 1964) are present in
the corresponding position but are actually different in struc-
ture. Possibly homologous sulci are present in lithobiomorphs,
in some species at least.
14. Eyes: (0) present; (1) absent.
All geophilomorphs are blind, whereas most lithobio-
morphs and many scolopendromorphs have ocelli, up to
about thirty per side in the former and up to four per side in
the latter. The complete regression of the eyes evolved
independently in different groups of centipedes, i.e.
in some lithobiomorph lineages, in the ancestor of
scolopendromorph family Cryptopidae and in the ancestor
of geophilomorphs.
15. Organ of Tomosvary: (0) present; (1) absent.
Absence of the organs of Tomosvary (also called the
postantennal organs) has been recognized as a synapomor-
phy of Epimorpha (see, e.g. Dohle, 1985).
Clypeus
16. Clypeus: (0) convex, projecting; (1) flat.
In all geophilomorphs, the clypeus is quite flat and devoid
of processes. In both lithobiomorphs and scolopendro-
morphs, the central part of the clypeal surface is swollen
and protruding ventrally.
17. Paraclypeal sutures: (0) parallel; (1) convergent poster-
iorly.
The paraclypeal sutures are at the lateral margins of the
clypeus, dividing the latter from the buccae. In most mecisto-
cephalid species, these sutures are convergent posteriorly
(Fig. 9A). In a few species, the lateral margins are subparallel,
A
DC
B
Fig. 8. Head (dorsal view) of some mecistocephalids. One antenna
as well as all antennal setae and sensilla are omitted. A, Anarrup
flavipes,/, subadult, Lombok; B, Dicellophilus anomalus, /, adult,
California; C, Tygarrup muminabadicus, /, subadult, Kashmir; D,
Mecistocephalus microporus, /, subadult, Cebu. Scales¼ 1mm.
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at least at mid-length (Fig. 9F). In most Adesmata, scolopen-
dromorphs and lithobiomorphs, the paraclypeal sutures are
not convergent.
18. Clypeus, areolation: (0) homogeneous; (1) marked on
the anterior part, virtually absent on the posterior part.
In all mecistocephalids, the anterior part of the clypeus
(areolate clypeus) is characterized by a marked areolation,
well visible even before handling the specimen with a clarifying
medium. The posterior part (clypeal plagula or plagulae) is
strongly sclerotized and not evidently areolate, the pattern of
scutes not being visible even after clarification. This condition
is common to all species, with the possible exception of the
enigmatic Megalacrus obscuratus, the clypeus of which has
been described as homogeneous (Attems, 1953). The distinc-
tion between an anterior and a posterior part of the clypeus has
already been recognized as a peculiar feature of mecistocepha-
lids (Hoffman, 1982). In the literature, however, different
authors recognized different parts in the clypeus, or at least
referred to the same parts by means of different terms. In
Adesmata, scolopendromorphs and lithobiomorphs, the cly-
peus is homogeneous and the areolation is variable in evidence.
19. Areolate clypeus, clypeal insulae: (1) absent; (2) present.
In some mecistocephalid species, one or more poorly areo-
late areas (clypeal insulae) are present inside the areolate
A B
F
GH
CD
E
Fig. 9. Clypeus, labrum and anterior part of buccae (ventral view) of some mecistocephalids. The areolation is omitted, but the margins of
areolate areas are indicated as dashed lines. A, Arrup holstii, /, subadult, China; B, Proterotaiwanella tanabei, /, subadult, Ryukyu Islands;
C, Anarrup flavipes, /, subadult, Lombok; D, Dicellophilus anomalus, /, adult, California; E, Tygarrup muminabadicus, /, subadult,
Kashmir; F, Takashimaia ramungula, ?, adult, Honshu; G, Mecistocephalus punctifrons, /, subadult, India; H, Mecistocephalus microporus,
/, subadult, Cebu. Scales¼ 0.5mm.
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surface of the anterior part of the clypeus (Fig. 9G). These
insulae are usually grouped on the posteromedian part
of the areolate clypeus. Conspecific individuals may be
very different in number, pattern, total extent and gradual
vs abrupt delimitation of these insulae. In a population
characterized by clypeal insulae, a few individuals may
completely lack them. Insulae are more frequent and
numerous in the oldest and largest individuals. Thus, as
far as possible, the occurrence of these areas in a species
has been checked in a series of specimens. This character
does not apply to the outgroup taxa, because their clypeus is
uniform and only slightly areolate. One or two finely areo-
late areas (called the ‘clypeal areas’) are known in some
Adesmata but they are most probably not homologous to
the clypeal insulae of mecistocephalids.
20. Clypeus, areolation on the central part: (0) virtually
absent; (1) present, as strong as on the remaining
areolate clypeus; (2) present, but weaker than on the
remaining areolate clypeus.
In mecistocephalids, a wide rhomboidal area in the mid-
dle of the clypeus may be areolate, with different degrees of
evidence. In some species, this area is virtually nonareolate,
like the posterior part of the clypeus, and it is thus con-
sidered part of the clypeal plagula (Fig. 9E). In other species,
it is areolate; thus, it is considered part of the areolate clypeus
(Fig. 9H). In this latter case, however, the areolation may be
as evident as in the remaining areolate clypeus or less
marked. Intraspecific variation is low; however, in some
species in which the central clypeus is areolate, the difference
between this central area and the remaining areolate
clypeus becomes more evident with growth. In lithobio-
morphs and scolopendromorphs, a clypeal part homo-
logous to the central part of mecistocephalid clypeus is
hardly recognizable. Despite this, the central part of the
clypeus may be considered virtually nonareolate, because
this is the condition of the whole clypeus.
21. Clypeus, mid-longitudinal areolate stripe: (0) absent;
(1) present.
A mid-longitudinal areolate stripe in the clypeus is exclu-
sive to some mecistocephalid species (Fig. 9A), whereas it is
lacking in the other mecistocephalids as well as in all other
centipede groups.
22. Clypeus, forward extension of the lateral part of the
clypeal plagula along the paraclypeal suture: (1) absent;
(2) at least half the length of the paraclypeal suture,
without a marginal areolate band; (3) at least half the
length of the paraclypeal suture, with a marginal
areolate band.
The relative extension of the clypeal plagula/ae is very
diverse among mecistocephalid species. The minimum
extension is in some Arrup, where the maximum length of
the two plagulae is 0.1–0.2 times the total length of the
clypeus. The maximum extension is in Anarrup, where the
only plagula covers the clypeus almost totally. The relative
extension of the lateral margins of the plagula/ae along the
paraclypeal margins is diverse too. In most mecistocephalid
species, the clypeal plagula/ae are largely in touch with the
paraclypeal margins (Fig. 9D). In some species, however, two
areolate bands extend backwards from the areolate clypeus
to separate the plagulae from the buccae (Fig. 9A). In other
species, the plagulae themselves seem to gradually become
areolate along the margins (Fig. 9F). This character does not
apply to the outgroup taxa, because the clypeal plagulae are
not defined in centipedes other than mecistocephalids.
23. Clypeus, setae at each antero-external corner: (0) none;
(1) one; (2) more than one.
In some mecistocephalid species, one to a few strong setae
develop at each anterolateral corner of the clypeus, quite
separate from the main array of clypeal setae (Fig. 9D,E).
In other species, conversely, no setae at all develop in this
position (Fig. 9F). The occurrence of these setae, however, is
quite variable among conspecific individuals. In the species
characterized by single setae, e.g. inTygarrup, these setae may
be undetectable in some of the youngest specimens; in the
species characterized by tufts of setae, e.g. in Dicellophilus
and in some Mecistocephalus, the number usually increases
during growth, possibly starting with only one seta at each
corner. As a consequence, this character was evaluated, as far
as possible, in series of individuals. No homologous setae
seem to occur in lithobiomorphs and scolopendromorphs.
In Adesmata, a high interspecific diversity is known.
24. Clypeus, setae on the lateral parts: (0) none; (1) on a
narrow transverse band; (2) on a wide surface.
Within mecistocephalids, the pattern of clypeal setae is
widely diverse. The number of setae ranges from only six in
some Mecistocephalus to about 100 in Dicellophilus. When
few in number, the setae are patterned and symmetrical;
when numerous they are scattered and irregularly distribu-
ted. In some species, the clypeal setae are limited to an
anteromedian area of the clypeus (Fig. 9F), whereas in
other species they evidently extend to the lateral parts of
the same. In this latter case, two conditions may be recog-
nized: one to two dozen setae, covering a wide but short
transverse band, as in some Tygarrup and Mecistocephalus
(Fig. 9E); more numerous setae, extending on a longer area,
as in Arrup and Dicellophilus (Fig. 9A). These basic patterns
are poorly affected by both the developmental increase in
the total number of setae and the interindividual variability
in number, position and symmetry. The other centipede
groups show a wide diversity in the pattern of setae, but the
setae usually do not extend to the lateral parts of the clypeus.
25. Clypeus, posteromedian pair of setae: (1) absent; (2)
present, close to the posterior margin of the clypeus; (3)
present, close to the centre of the clypeus.
In most mecistocephalids, a pair of strong setae may be
easily distinguished from the other clypeal setae. This pair is
placed posterior to all other setae, either at mid-length on
the clypeus (in most species; Fig. 9E) or close to the poster-
ior margin (in someDicellophilus; Fig. 9D). This character has
not been coded for the outgroup taxa, because homologies
among different patterns of clypeal setae are very dubious.
26. Clypeus, lateral groups of buttonlike sensilla: (0) absent;
(1) present.
In mecistocephalids, buttonlike sensilla are usually
spread among the clypeal setae. Two additional groups of
similar sensilla, however, are present in some species. These
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sensilla are evident on the lateral parts of the clypeus, often
at the antero-external corners of the plagula/ae (Fig. 9H).
The number of these sensilla increases during growth, but
their occurrence seems invariant among conspecifics. In the
literature, the emergence sockets of these sensilla were erro-
neously interpreted as glandular pores (e.g. Verhoeff, 1934;
Takakuwa, 1937).
27. Clypeus, micropores: (0) absent; (1) present.
In some mecistocephalid species, the clypeal plagula/ae
are pierced with several scattered micropores [so called by
Crabill (1970); probably the same as the ‘micropores’ of
Turcato et al. (1995)]. The occurrence of similar pores in
other centipede groups is largely ignored, but our prelimin-
ary observations detected them in some scolopendro-
morphs.
Bucca
28. Bucca, spiculum: (0) absent; (1) present.
The spiculum (Fig. 9F) is a strongly sclerotized process,
pointed forwards and present on the most anterior part of
each bucca, in some mecistocephalid species only.
29. Bucca, stilus: (0) absent; (1) present.
In all mecistocephalids, the internal margin of each bucca
is shaped as a thickened stick (stilus), which is characterized
by an anterior pointed tip and an internal notch on the
anterior part (Fig. 9A). All other centipede groups lack
these structures.
30. Bucca, areolation on the anterior part: (0) absent;
(1) present.
In all mecistocephalids, the anterior part of each bucca is
evidently areolate, whereas the remaining part is not
(Fig. 9A). In all other centipede groups, the buccae are
usually homogeneously nonareolate.
31. Bucca, areolation along the paraclypeal margin:
(0) absent; (1) present, very narrow, as in Fig. 9(C);
(2) present, as wide as in Fig. 9(E); (3) present, very
wide, as in Fig. 9(H).
In all mecistocephalids, the areolation of the anterior part
of each bucca extends as a band along the paraclypeal
suture. The relative width of this band is different in differ-
ent species, and three conditions are recognized here
(Fig. 9C,E,H). A similar areolate band is lacking in all
other centipede groups.
32. Bucca, setae on the anterior half: (0) absent or very tiny;
(1) present, long.
In a few mecistocephalid species, a group of strong and
long setae develops on the anterior half of each bucca
(Fig. 9C). In the other species, only short processes, similar
to buttonlike sensilla, may be present. Anterior buccal setae
are also present in some Adesmata.
33. Bucca, setae on the posterior half: (0) absent; (1) present.
In some mecistocephalid species, the posterior half of
each bucca is covered with a group of strong and long
setae, completely lacking in other species. Posterior buccal
setae are also present in some Adesmata.
Labrum
34. Labrum, side-piece, transverse thickened line: (0) absent;
(1) present.
In all mecistocephalids, the labrum is composed of three
sclerites, a mid-piece and a pair of side-pieces. Each
side-piece is divided into two parts (alae) by a thickened
transverse line (Fig. 9A). This line, however, is weak or
discontinuous in miniaturized species such as Nannarrup
hoffmani (see Foddai et al., 2003) and in juveniles of
other species. This line was sometimes considered a
true suture between sclerites (Hoffman, 1982; Edgecombe
et al., 1999). In all other centipede groups, the side-pieces
seem to be undivided. In some Adesmata, however, the
shape and structure of the labrum are so modified that
homologous relationships are difficult to recognize. The
labrum of the schendylids, for instance, was interpreted as
divided into alae like those of mecistocephalids (Crabill,
1970).
35. Labrum, side-piece, transverse thickened line:
(1) straight; (2) curved, convex forwards; (3) sinuous,
convex forwards on the internal part, backwards on
the external part; (4) curved, convex backwards.
The shape of the transverse thickened line of the labrum
side-piece is different in different mecistocephalid species.
Four different conditions may be recognized, i.e. straight
(Fig. 9E), convex forwards (Fig. 9D), sinuous (Fig. 9B) and
convex backwards (Fig. 9F). This character does not apply
to the outgroup taxa because the thickened lines are present
in mecistocephalids only.
36. Labrum, anterior ala, internal margin: (1) reduced to a
pointed end; (2) long.
In some mecistocephalid species, the internal margin of
the anterior ala is very reduced in length, with respect to the
internal margin of the posterior ala (Fig. 9C). In other
species, it is significantly elongate, its length comparable,
although shorter, with the length of the internal margin of
the posterior ala (Fig. 9G). This character does not apply to
the outgroup taxa because the thickened lines are present in
mecistocephalids only.
37. Labrum, posterior margin, backwards convexity:
(0) present; (1) absent.
In most mecistocephalid species, the posterior margin of
the labrum extends backwards in a weak convexity on its
internal half (Fig. 9A). In a few species only, the entire margin
is homogeneously concave (Fig. 9D). In lithobiomorphs,
scolopendromorphs and Adesmata, a convexity is usually
present, sometimes even more pronounced than in mecisto-
cephalids.
38. Labrum, side-piece, posterior margin, medial process:
(0) absent; (1) present.
In a few mecistocephalid species, the postero-internal
corner of each labral side-piece extends to a short but
evident subrectangular process. In the other species, this
corner is either not pronounced or extends into a tiny
tooth only.
39. Labrum, side-piece, longitudinal stripes: (0) absent;
(1) present.
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Longitudinal stripes, alternatively lighter and darker,
typically appear on the posterior alae in a few species of
mecistocephalids (Fig. 9C).
40. Labrum, side-piece, posterior margin, medial notches:
(0) absent; (1) present.
In a few mecistocephalid species only, the most internal
part of the posterior margin of each labrum side-piece is
marked by a short series of distinct notches (Fig. 9B). In
other mecistocephalids, the entire posterior margin is either
partially crenate or not crenate.
41. Labrum, hairlike dorsal processes: (0) present;
(1) absent.
Within mecistocephalids, either papillae or short hairlike
processes cover a pair of peculiar sclerites placed dorsal
to the labral side-pieces. The occurrence of these processes
was checked by observing the labrum from below, by
light transmission. The occurrence, size and extension of
these processes are highly variable among conspecific
individuals. Accordingly, they were evaluated, as far as
possible, in series of specimens and were scored as
present when observed in at least some conspecifics. Tenta-
tively, we regard similar processes known in some groups
of Adesmata as homologous to those in mecisto-
cephalids. This character has often been dramatically
misinterpreted. In some mecistocephalid species, ‘hairs’
were erroneously described as present along the
posterior margin of the labrum only, as in some Mecisto-
cephalus traditionally assigned to the subgenera Brachyptyx
and Dasyptyx (see Silvestri, 1919; Chamberlin, 1920a, b;
Attems, 1929; Takakuwa, 1937, 1940, 1942); in other
species, different authors disagree as to whether the
labrum is ‘hairy’ or not, as in Tygarrup javanicus (see
Attems, 1907, 1926, 1928, 1929; Demange, 1981; Lewis &
Rundle, 1988).
42. Labrum, fringe along the posterior margin: (0) absent;
(1) present.
A fringe of hairlike projections is present along the pos-
terior rim of the labrum side-pieces in some mecisto-
cephalid species (Fig. 9D). These projections are
distinguished from the shorter hairlike processes covering
the additional dorsal sclerites (see ch. 41). Elements of
the fringe are longer and less flexible than the dorsal
hairlike processes and their occurrence may be independent
of the latter. They were described in the literature
under different names, because they were sometimes not
distinguished from the dorsal hairlike processes or other
projections. In mecistocephalids, only a few species actually
have a fringe and no intraspecific variability occurs. In
other species, however, some dorsal hairlike processes
may also be visible along the labral margin, but they
appear structurally different from the elements of the
fringe and their occurrence is largely variable. Different
conditions may be recognized in Adesmata. In scolopendro-
morphs, branched projections along the labrum margin
are tentatively recognized here as homologous to the
fringe. In lithobiomorphs, different projections (branching
bristles) develop on the dorsal surface of the labrum rather
than along the margin.
43. Paralabial sclerites: (0) present; (1) absent.
Two paralabial sclerites are found beside the labrum side-
pieces in most centipede groups, but are virtually absent in
most geophilomorphs, including mecistocephalids.
Mandible
44. Mandible, basal tooth: (0) rounded; (1) subconic.
A basal tooth is borne on the dorsal margin of the man-
dible, at the base of the first lamella (Fig. 10A). It is subconic
in all mecistocephalid species, except for the enigmatic
Megalacrus obscuratus, which is described as lacking a
mandibular tooth (Attems, 1953). This tooth is rounded in
all lithobiomorphs and scolopendromorphs, whereas Ades-
mata show diverse conditions.
45. Mandible, dentate lamellae: (0) present; (1) absent.
In geophilomorphs, two types of mandibular lamella are
traditionally recognized, i.e. the dentate lamellae (one or
none on each mandible) and the pectinate lamellae (one to
several on each mandible). In mecistocephalids, all mandib-
ular lamellae are quite similar to each other and are uni-
versally considered homologous to the pectinate lamellae of
A
B
Fig. 10. A, Mandible of a mecistocephalid (Tygarrup muminaba-
dicus, /, subadult, Kashmir); B, hyaline scales on the medial
projection of the first maxillae (dorsal view) in a mecistocephalid
(Arrup dentatus, /, adult, Hokkaido). Scales¼ 0.1mm.
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the other geophilomorphs, whereas no dentate lamellae are
thought to be present (Fig. 10A). In Adesmata, very differ-
ent conditions evolved in different groups, but an array of
one dentate lamella followed by some pectinate lamellae is
recognizable as the ancestral condition. In both lithobio-
morphs and scolopendromorphs, at least one dentate
lamella is always present.
46. Mandible, number of fully developed pectinate lamellae:
(0) 1; (1) 4–5; (2) 6–7; (3) 8–12; (4) 15–25.
The number of pectinate lamellae (Fig. 10A) is very vari-
able among mecistocephalid species, ranging from very few
(four in most Arrup species, but only two recorded in sub-
adult Arrup pylorus; see Chamberlin, 1920c) to twenty-seven
(in adult Mecistocephalus gigas Haase, 1887). Because the
number is quite variable among conspecific individuals and
increases appreciably during growth, the average number in
the adult stage was checked for each species on a series of
specimens. Because on each mandible the series of lamellae
fades ventrally into some final rudimentary elements, only
the fully developed lamellae were counted. The mandible of
lithobiomorphs and scolopendromorphs, although well
known and very conservative, is hard to compare with
that of geophilomorphs, particularly with that of mecisto-
cephalids. In lithobiomorphs and scolopendromorphs,
numerous elongate projections (‘aciculae’) are inserted on
each mandible close to the dentate lamella. These elements
are probably homologous to the pectinate lamellae of geo-
philomorphs (Cook, 1896; Edgecombe et al., 1999;
Edgecombe & Giribet, 2002), but the actual number of
homologous elements is difficult to assess. Most authors
(e.g. Eason, 1964; Lewis, 1981) tentatively recognized only
one element in lithobiomorphs and a few elements in scolo-
pendromorphs. Because uncertainty persists, we preferred
to code this character as unknown in the outgroup species
Lithobius forficatus and Cryptops anomalans. In all Ades-
mata, at least one pectinate lamella is recognizable, but its
shape is highly different in different families.
47. Mandible, pectinate lamella, size of teeth: (0) changing
gradually along the lamella; (1) changing abruptly
along the lamella.
In each mandibular pectinate lamella, the size and length
of the teeth increase from the most basal teeth to the tip of
the lamella. The transition is gradual in most mecistocepha-
lids, but it is evidently abrupt in a few species. We have
evaluated this character in one of the intermediate lamellae,
because in the first lamella all teeth appear quite similar and
in the rudimentary lamellae teeth are not well developed.
The state of this character has been coded as unknown in
both lithobiomorphs and scolopendromorphs because of
the difficulty in recognizing mandibular elements homo-
logous to geophilomorph lamellae and teeth (see ch. 46).
48. Mandible, ‘hairs’ on the ventral surface: (0) absent;
(1) present.
In a few mecistocephalid species, the ventral surface of
the mandible is covered with thick short ‘hairs’ at the base
of the rudimentary lamellae. In all lithobiomorphs, in scolo-
pendromorphs and at least in the Adesmata considered here,
this mandibular region is not hairy. Descriptions available in
the literature for some species are ambiguous because ‘hairs’
and lamellar rudiments were sometimes confused.
49. Mandibular fulcrum: (0) well developed; (1) reduced
and displaced.
The fulcra are a pair of articulatory sclerites between the
mandibles and the cephalic shield. They are very reduced in
all mecistocephalids, in contrast to all other centipede groups.
First maxillae
50. First maxillae, coxosternum, ratio of width to length:
(0) 4.0–4.8; (1) 3.3–3.6; (2) 2.3–2.8; (3) 1.8–2.2.
Within mecistocephalids, the degree of elongation of the
coxosternum of the first maxillae (Fig. 11) is variable among
species. The ratio of maximum width to medial length was
evaluated after dissecting the maxillary complex and flat-
tening the coxosternum completely. Ratios were generally
clustered around three modal values, thus allowing us to
recognize tentatively as many intervals. A fourth interval
was defined for the outgroup taxa. Allometric changes
occur during growth as well as slight interindividual vari-
ability, thus the ratio was calculated, as far as possible, for a
series of conspecific adults or subadults. In lithobiomorphs,
scolopendromorphs and most Adesmata, the coxosternum
is less elongate than in mecistocephalids.
51. First maxillae, coxosternum, antero-external corners:
(0) absent; (1) present.
Within mecistocephalids, the first maxillary coxosternum
takes either of two alternative shapes. In some species, the
lateral margins are convergent forwards and about aligned
with the external margins of the telopodites (Fig. 11A). In
the other species, the coxosternum is expanded in antero-
external corners, either rounded or pointed (Fig. 11B,F).
52. First maxillae, coxosternum, pointed process on each
antero-external corner: (0) absent; (1) present.
In some mecistocephalid species, the coxosternum of the
first maxillae is characterized by a pair of anterolateral
pointed corners (Fig. 11F). Similar pointed processes do
not occur in the other centipede groups.
53. First maxillae, coxosternum: (0) divided mid-
longitudinally, ventral surface nonareolate; (1) undivided
mid-longitudinally, ventral surface areolate.
In most mecistocephalid species, the first maxillary coxo-
sternum is divided into lateral halves by a sutural line,
which is evident in all individuals (Fig. 11B). In a few spe-
cies, however, the coxosternum is undivided, at least on the
ventral surface, as also confirmed by the presence of a
continuous areolation on the intermediate part (Fig. 11A).
Postembryonic development does not change the structure
of the coxosternum, and no interindividual differences
occur. Within Adesmata, the coxosternum is undivided in
most lineages, but it is evidently divided in neogeophilids
(Crabill, 1969), which are regarded as basal Adesmata by
Foddai & Minelli (2000). In centipedes other than geophi-
lomorphs, the coxosternum is usually divided mid-
longitudinally. The actual structure of the coxosternum in
some species of Arrup has often been misunderstood, thus
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supporting erroneous genus-level taxonomic arrangements.
Some authors described the coxosternum as divided mid-
longitudinally, as in the other mecistocephalids (see
Brolemann, 1909; Chamberlin, 1912; Takakuwa, 1934, 1940;
Takashima & Shinohara, 1952). Indeed, a weak medial line is
visible on the coxosternum of some specimens, but this is not
actually a suture, rather it probably marks internal muscular
attachments [as recognized by Crabill (1964)].
54. First maxillae, coxosternum, areolation along the ante-
rior margin: (0) absent; (1) present.
In all mecistocephalid species, areolation occurs along the
anterior margin of the first maxillary coxosternum, at the
base of the medial projections and the telopodites (Fig. 11).
This areolation is not present in Adesmata, at least in the
taxa considered here. It has been observed in scolopendro-
morphs, but not in lithobiomorphs.
55. First maxillae, coxosternum, setae: (0) present; (1) absent.
In some mecistocephalid species, one to a few setae
develop on the antero-internal corner of each of the two
halves of the first maxillary coxosternum (Fig. 11B). In
these species, the number and size of the setae may differ
among conspecifics, but some setae are always present in all
individuals. In other species, the coxosternum is invariably
devoid of setae (Fig. 11A). The condition is variable within
Adesmata, whereas in both lithobiomorphs and scolopen-
dromorphs, setae are always lacking.
56. First maxillae, medial projection, ratio of length to
width: (0) 0.7–1.2; (1) 1.3–1.9; (2) 2.0–2.6; (3)>4.0.
In the firstmaxillae ofmecistocephalids, twopairs of append-
ages are articulated on the anterior margin of the coxosternum
(Fig. 11). The internal and external appendages are traditionally
referred to as the medial projections (also called the coxal
projections) and the telopodites, respectively. The relative
elongation of themedial projections is very different in different
species. Itwas evaluated here as the ratio between the length and
the maximum width. This ratio ranged from <1 to about 3,
exceptionally to>4. InMecistocephalus longichilatus, the distal
hyaline parts of the projections are exceptionally elongate, over-
reaching the anterior margin of the cephalic shield (Takakuwa,
1936). Because the ratio may vary among conspecific individ-
uals, it was calculated, as far as possible, on series of
specimens for each species. The elongation is variable within
Adesmata, scolopendromorphs and lithobiomorphs.
57. First maxillae, medial projection: (0) evenly sclerotized;
(1) basal part sclerotized, distal part hyaline.
In all mecistocephalids, the medial projections appear as
independent sclerites articulated to the coxosternum and
each bears a more sclerotized basal part and a hyaline distal
part. In Adesmata, scolopendromorphs and lithobio-
morphs, the medial projections are structurally continuous
with the coxosternum and evenly sclerotized.
58. First maxillae, medial projection, distal part: (0) not
enlarged; (1) enlarged, subtriangular; (2) enlarged, sub-
elliptical.
Within mecistocephalids, the shape of the distal hyaline
part of each medial projection is very different in different
species. In some species it is homogeneous in width
(Fig. 11A); in others it is enlarged, either in a subelliptical
(Fig. 11E) or a subtriangular shape (Fig. 11C). In the
exceptional case of Mecistocephalus longichilatus (see ch.
56), the hyaline parts are evenly narrowed to the tip. In
Adesmata, scolopendromorphs and lithobiomorphs, the dis-
tal parts of the medial projections are generally not enlarged.
59. First maxillae, medial projection, hyaline scales:
(0) absent; (1) present.
In some mecistocephalid species, the medial projections
of the first maxillae have peculiar hyaline scales (Fig. 10B).
These scales are arranged in a narrow band, longitudinally
aligned on the dorsal surface and close to the internal
margin of the projection. The number of scales increases
during growth, but their presence is invariant within a
species. These scales have never been described or illu-
strated for mecistocephalids. Thus, this character has
been coded as unknown for all the species not directly
studied by us. Very little information is available for a few
species of Adesmata recently illustrated in taxonomic papers.
60. First maxillae, telopodite, length to width ratio:
(0) 1.0–1.6; (1) 2.3–2.8; (2) 3.0–3.8; (3)>4.0.
Within mecistocephalids, the elongation of the first max-
illary telopodites is different in different species. The ratio of
the maximum length to the maximum width was evaluated.
This ratio ranged mostly from about 2 to about 4, falling into
two separate intervals. Mecistocephalus longichilatus, how-
ever, is exceptional in having the hyaline parts of the telopo-
dites so elongate as to overreach the anterior margin of the
cephalic shield (Takakuwa, 1936). The ratio may be variable
among conspecific individuals. Thus, it was calculated, as far
as possible, on a series of individuals for each species. In
Adesmata, scolopendromorphs and lithobiomorphs, telopo-
dites are relatively stout.
61. First maxillae, telopodite, articles: (0) 2; (1) 1.
In all mecistocephalids, each telopodite of the first
maxillae is invariably composed of only one sclerite,
even though a more sclerotized basal part contrasts with
a hyaline distal part, like the medial projections (see ch.
57). In lithobiomorphs and scolopendromorphs, the
telopodites are composed of two articles, whereas within
Adesmata they are composed of either one or two articles.
Second maxillae
62. Second maxillae, coxosternum: (0) undivided; (1)
divided mid-longitudinally.
In most mecistocephalid species, the coxosternum of the
second maxillae appears as an undivided sclerite, although
the median part is quite short (Fig. 11D). Only in two
species is the coxosternum divided into halves by a complete
mid-longitudinal sutural line, clearly visible on the ventral
surface (Fig. 11B). In scolopendromorphs and lithobio-
morphs, the coxosternum is also divided. In many Adesmata,
it is undivided; in the other ones a sutural line is present.
63. Second maxillae, coxosternum, ratio of maximum length
to medial length: (0) 3.3–5.0; (1) 2.2–3.0; (2) 1.6–2.2.
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We evaluated the ratio between the maximum length
(from the telopodite-bearing processes to the posterolateral
corners) and the medial length (between the anterior and
the posterior concave margins of the median part) as a
proxy for the general shape of the second maxillary coxos-
ternum. Within mecistocephalids, three intervals are tenta-
tively recognized. Because of allometric growth and
interindividual variability, measures were taken, as far as
possible, from series of conspecific adults.
64. Second maxillae, coxosternum, median part: (0) hyaline,
different from the lateral parts; (1) sclerotized, con-
tinuous with the lateral parts.
In most mecistocephalid species, the second maxillary cox-
osternum is evenly sclerotized in the intermediate part as well
as in the lateral parts, the former thus appearing continuous
with the latter (Fig. 11E). In some species, the two sclerotized
halves are connected by a diaphanous membranous part,
distinct from the lateral parts (Fig. 11A). In Adesmata, the
A B
D
C
E F
Fig. 11. First and second maxillae (ventral view) of some mecistocephalids. Only the right half of the whole maxillary complex is illustrated.
The areolation is omitted, but the margins of areolate areas are indicated as dashed lines. A, Arrup holstii, /, subadult, China; B, Anarrup
flavipes, /, subadult, Lombok; C, Dicellophilus anomalus, /, adult, California; D, Tygarrup javanicus, /, subadult, Halmahera; E,
Mecistocephalus tahitiensis, /, adult, Palawan; F, Mecistocephalus microporus, /, subadult, Cebu. Scales¼ 0.2mm.
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median part is also usually sclerotized. In both lithobiomorphs
and scolopendromorphs, there is a hyaline connection.
65. Second maxillae, coxosternum, areolation on the median
part: (0) virtually absent; (1) present, evident.
In most mecistocephalid species, the intermediate region of
the second maxillary coxosternum is areolate (Fig. 11C). Even
in the species with a hyaline connection (see ch. 64), the inter-
nal margins of the sclerotized lateral halves are areolate
(Fig. 11A). In some species, however, areolation is completely
lacking on the median part of the coxosternum (Fig. 11B). In
Adesmata, scolopendromorphs and lithobiomorphs, the entire
intermediate part of the coxosternum is virtually nonareolate.
66. Second maxillae, coxosternum, smooth insulae on the
median band: (1) absent; (2) present.
The areolation covering the intermediate part of the sec-
ond maxillary coxosternum may fade in subcircular areas,
which appear nonareolate (Fig. 11E). These areas, called
smooth insulae, are variable in number, diverse in extent
and irregularly placed. When particularly wide, they may be
coalescent, to form an entire mid-longitudinal nonareolate
band (Fig. 11F). Smooth insulae occur in some species only.
The number and extent are largely variable among individ-
uals, possibly related to age, and insulae may be lacking in
some individuals. Thus, species were coded as lacking smooth
insulae after checking more than one specimen. This character
does not apply to the species lacking areolation on the median
part of the coxosternum, all outgroup taxa in particular.
67. Second maxillae, coxosternum, areolation on a posterior
band: (0) virtually absent; (1) present, evident.
In some mecistocephalid species, the areolation of the
second maxillary coxosternum extends to a wide transverse
band, which runs along the posterior margin between the
two postero-external corners (Fig. 11E).
68. Second maxillae, coxosternum, areolation on the lateral
parts: (0) virtually absent; (1) present, evident.
In a few mecistocephalid species, the areolation covers the
lateral parts of the second maxillary coxosternum
extensively, whereas in other species it is limited to the
intermediate and posterior parts (Fig. 11E). Differences
in the degree of areolation may be observed
among conspecific individuals. Therefore, more than
one specimen was checked for each species, whenever pos-
sible.
69. Second maxillae, metameric pore and foraminal process:
(0) groove from the metameric pore running towards
the posterior margin of the coxosternum, foraminal
process not detectable; (1) groove from the metameric
pore running towards the postero-external corner
of the coxosternum, foraminal process reaching
the postero-external corner of the coxosternum;
(2) groove from the metameric pore running towards
the lateral margin of the coxosternum, foraminal
process not reaching the postero-external corner of
the coxosternum.
Within mecistocephalids, the postero-external regions of
the second maxillary coxosternum may exhibit either of two
conditions (Fig. 11A,B) differing in the position of the
metameric pore, the length and the direction of the groove
running from the pore and the elongation of the foraminal
process, i.e. the narrow projection lateral to the pore. In
lithobiomorphs and Adesmata, the arrangement is different
from those found in mecistocephalids. The metameric pores
are not detectable in scolopendromorphs. Thus, the char-
acter does not apply to the relevant outgroup species. Until
now, the taxonomic value of this character was largely
underestimated. Only Crabill (1964) discussed it critically,
hypothesizing an evolutionary trend from metameric pores
opening backwards to pores opening laterally, but only on a
speculative basis.
70. Second maxillae, telopodite, first article, ratio of length
to width: (0) 2.4–4.0; (1) 1.0–2.0.
In most mecistocephalid species, the first article of the
second maxillary telopodite is long and slender (Fig. 11B),
whereas in other species it is stout (Fig. 11A). This differ-
ence was evaluated as the ratio of the maximum length to
the maximum width.
71. Second maxillae, telopodite, distal article, ratio of length
to width: (0) 1.8–3.5; (1) 1.3–1.6.
In a few mecistocephalid species, the distal article of the
second maxillary telopodite is quite swollen, wider than
the second article (Fig. 11B); in most species it is
slender (Fig. 11D); in Takashimaia ramungula it is typically
constricted. This difference was evaluated by the ratio of
the maximum length to the maximum width of the
distal article. Only two intervals were recognized because the
ratio is affected by allometric changes during growth, by
interindividual differences and (rarely) by asymmetry.
72. Second maxillae, telopodite, praetarsus: (0) present;
(1) absent.
In most mecistocephalid species, the second maxillary
telopodite bears a tiny apical claw, the praetarsus
(Fig. 11E), usually a subconic rigid process, slightly curved
inwards. Its shape is highly variable, even between the two
telopodites of the same specimen, possibly because of devel-
opmental problems or secondary damage due to feeding
activity. It often bears short accessory spines at the base
and, in rare instances, it is forked. Sometimes it is not
pointed but in the shape of a stout tubercle crowned with
short spines. In all these species, however, the praetarsus is
present in all individuals, independent of age or sex. In
other species, the praetarsus is regularly lacking
(Fig. 11A). In both lithobiomorphs and scolopendro-
morphs, the praetarsus is always present, in the shape of a
well-developed claw, more evident than in mecistocepha-
lids. Accessory processes are also typically present. In Ades-
mata, the praetarsus is highly variable among species, from
well developed to completely absent (see Borucki, 1996).
73. Second maxillae, telopodite, distal article, setae on the
external side: (0) less numerous than on the internal
side; (1) as numerous as on the internal side.
In most mecistocephalid species, the setae covering the
third article of the second maxillary telopodite are not evenly
placed on the entire surface. They are usually aggregated on
the internal distal part of the article, but virtually absent on
the proximal external side of the same article (Fig. 11E). Only
in a few species, the setae are dispersed almost evenly on the
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entire surface of the article (Fig. 11B). In Adesmata, litho-
biomorphs and scolopendromorphs, at least in the outgroup
species considered here, the pattern of setae is heterogeneous,
as in most mecistocephalids.
Forcipular segment
74. Forcipular segment, tergum, length to width ratio: (0)
0.2; (1) 0.4–0.5; (2) 0.6–0.8.
All mecistocephalids are characterized by the reduction
of the width of the forcipular tergum and by the corres-
ponding dorsal overgrowth of the forcipular pleura. Two
different degrees of reduction occur in different species, as
expressed by the ratio between the medial length and the
maximum width of the tergum (Fig. 12A,B). In some spe-
cies, e.g. in Anarrup flavipes, an additional sclerite, tiny and
weakly sclerotized, is visible just anterior to the forcipular
tergum. This sclerite, possibly recognizable as a praetergum,
was disregarded when measuring the tergum. This character
does not apply to scolopendromorphs because in this group
an independent forcipular tergum is not recognizable: in all
scolopendromorphs, a single large tergum covers the for-
cipular segment and the first leg-bearing segment; this scler-
ite was often considered to be derived from the ‘fusion’ of
the forcipular tergum and the following tergum (Eason,
1964; Lewis, 1981), but its developmental and evolutionary
origin is actually unknown. In all lithobiomorphs and in
most Adesmata, the forcipular tergum is about as wide as
the whole forcipular segment. Thus, the ratio considered
A B
C D
Fig. 12. Forcipular segment (dorsal view; head detached) of some mecistocephalids. Only the left forcipule is illustrated. The areolation of the
tergum is omitted, but the margins of areolate areas are indicated as dashed lines. Setae on pleurae and forcipules are omitted. A, Arrup
dentatus, /, adult, Hokkaido; B, Takashimaia ramungula, ?, adult, Honshu; C, Mecistocephalus tahitiensis, /, adult, Palawan; D,
Mecistocephalus microporus, /, subadult, Cebu. Scales¼ 1mm.
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here is very low. In some geophilids, the tergum is strongly
reduced, as in mecistocephalids.
75. Forcipular segment, tergum, areolation: (0) uniform; (1)
evident along the anterior and the lateral margins,
virtually absent on the remaining surface; (2) evident
along the anterior and the lateral margins and along 2
paramedian stripes, virtually absent on the remaining
surface.
In most mecistocephalid species, the areolation on the
forcipular tergum is virtually limited to a broad band run-
ning along the anterior and lateral margins (Fig. 12B). In a
few species, it also extends along two paramedian stripes. In
a few other species, the entire surface of the tergum is
uniformly areolate. Because of interindividual variability,
both in the extension and the appearance of the areolation,
each species was coded according to the most frequent
pattern. This character does not apply to scolopendro-
morphs because in this group an independent forcipular
tergum is not recognizable (see ch. 74). In lithobiomorphs
and Adesmata, the areolation is so weak that the entire
tergum appears to be uniformly areolate.
76. Forcipular segment, tergum, mid-longitudinal sulcus: (0)
virtually absent; (1) present.
In mecistocephalids, a mid-longitudinal furrow may be
present on the anterior part of the forcipular tergum
(Fig. 12B). Its occurrence was checked under incident
light. Its presence is quite variable among conspecific indi-
viduals, but the species with a distinct sulcus may be distin-
guished from those in which no more than a trace is
detectable. This character does not apply to scolopendro-
morphs because in this group an independent forcipular
tergum is not recognizable (see ch. 74). In both lithobio-
morphs and Adesmata, no furrow is visible.
77. Forcipular segment, pleuron, dorsal ridge: (0) virtually
absent, not sclerotized; (1) present, well sclerotized.
In some mecistocephalid species, a shallow dorsal ridge
runs longitudinally on each forcipular pleuron (Fig. 12C).
Species bearing distinct sclerotized ridges were distin-
guished from those in which no more than a trace was
detectable under incident light. In all other centipede
groups, the forcipular pleura do not have ridges.
78. Forcipular segment, pleuron, scapular point: (0) reaching
the anterior margin of the coxosternum; (1) not
reaching the anterior margin of the coxosternum.
The position of the anterior tips of the forcipular pleura
(scapular points) in relation to the forcipular coxosternum
was observed from above after removing the head. In some
mecistocephalid species, the pleura extend forward to reach
the anterior margin of the coxosternum and in some cases
they overreach the margin (Fig. 12C). In other species, the
scapular points are far from the coxosternal margin
(Fig. 12A).
79. Forcipular segment, pleuron, scapular point: (0) not
elongate; (1) elongate.
In a few mecistocephalid species, the anterior tip of each
forcipular pleuron (scapular point) is evidently elongate as a
slender projection (Fig. 12B). In the other species, as well as
in the outgroup taxa, it appears stout (Fig. 12A).
80. Forcipular segment, coxopleural sutures: (0) anterior
part dorsal, posterior part ventral; (1) entirely ventral.
In all mecistocephalids, the coxopleural sutures, i.e. the
sutures between the forcipular coxosternum and the pleura
of the same segment, run ventrally in their posterior part,
turning dorsally in their anterior part (Fig. 12). The condi-
tion is the same in all lithobiomorphs and in a few Ades-
mata. In scolopendromorphs and most Adesmata, these
sutures run on the ventral side for their whole length.
81. Forcipular segment, coxosternum, chitin-lines: (0) absent;
(1) present.
Chitin-lines are a pair of sclerotized paramedian lines
present on the ventral surface of the forcipular coxoster-
num. They are characteristic of some Adesmata, e.g. geo-
philids, but they are always lacking in mecistocephalids.
82. Forcipular segment, coxosternum, condylar processes:
(0) absent; (1) present.
In a few mecistocephalid species, a pair of elongate for-
ward pointing projections emerge from the anterior margin
of the forcipular coxosternum, close to the dorsal condyli of
the articulations between the coxosternum and the trochan-
teropraefemur (Fig. 12B). These projections are here called
the condylar processes. They may be well sclerotized, slen-
der and sinuous. Some interindividual variability in the
degree of elongation occurs. Similar projections are com-
pletely absent in most mecistocephalid species (Fig. 12A), as
well as in the other centipede groups, at least in the out-
group species considered here.
83. Forcipular segment, coxosternum, anterior marginal
teeth: (0) absent; (1) present.
In most mecistocephalid species, a pair of short teeth is
present on the anterior margin of the forcipular coxoster-
num (Fig. 12A), but these teeth are variably distinct among
individuals. In a few species, the teeth can be considered as
virtually absent because only two shallow processes are
present. In lithobiomorphs, scolopendromorphs and Ades-
mata, no teeth of this kind are present. Anterior plates, each
with two to eleven tiny teeth, are inserted on the anterior
margin of the coxosternum in all lithobiomorphs and in
some scolopendromorphs. These plates, however, are not
considered homologous to the teeth of mecistocephalids
because their anatomical position is not the same.
84. Forcipular segment, coxosternum, cerrus, lateral groups
of setae: (0) absent; (1) present.
In mecistocephalids, a system of short setae (cerrus) is
usually present on the dorsal surface of the forcipular coxo-
sternum (Crabill, 1970). It appears quite variable in extent and
pattern, but it can easily be described as composed of a lateral
group and a paramedian row on each side (Fig. 12D), usually
well separated but sometimes coalescent. The cerrus is often
virtually absent in juveniles: the setae appear and increase in
number during growth. The cerrus is regularly present in some
species, but completely absent in others. The occurrence and
pattern of the cerrus were observed after detaching the head
from the trunk. The occurrence of the lateral groups is quite
independent from that of the paramedian rows (Fig. 12B). In
the outgroup taxa, at least in the species considered, no setae
are present on the dorsal surface of the coxosternum. In
Evolution of segment number in Mecistocephalidae 571
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
lithobiomorphs, a few small setae are present on the anterior
plates only, but these are not interpreted as a cerrus.
85. Forcipular segment, coxosternum, cerrus, paramedian
rows of setae: (0) absent; (1) present.
In some mecistocephalid species, the cerrus (see ch. 84)
includes, in addition to the lateral groups of setae, two
paramedian rows of setae. These rows are typically conver-
gent forwards, either straight or widely curved (Fig. 12D).
Usually the setae are quite precisely aligned, but in Mecis-
tocephalus punctifrons and other species they are scattered
inside two wide bands.
86. Forcipular segment, trochanteropraefemur, length to
width ratio: (0) 1.7–1.9; (1) 0.6–1.2; (2) 1.3–1.6;
(3) 2.0–2.1.
The elongation of the forcipular trochanteropraefemur
was expressed as the ratio between the length and the max-
imum width of the article. The length was conventionally
measured in dorsal view, after detaching the head, as the
distance between the two condyli (Fig. 12). The width was
measured at mid-length, perpendicular to the lateral sides.
To cope with possible allometric changes and interindividual
variability, the ratio was calculated, whenever possible, from
series of conspecific adults. Within mecistocephalids, four
intervals were tentatively recognized. In lithobiomorphs and
scolopendromorphs, the trochanteropraefemur is not very
elongated, whereas in Adesmata different conditions occur.
87. Forcipular segment, ratio of trochanteropraefemur length
to coxosternum width: (0) 0.2–0.6; (1) 0.6–0.7; (2) 0.7–0.8.
The ratio between the length of the forcipular trochanter-
opraefemur and the width of the corresponding coxoster-
num was used to describe the general elongation of the
forcipules with respect to the body. Both measures were
taken in dorsal view after detaching the head (Fig. 12): for
the trochanteropraefemur, the distance between the dorsal
condyli; for the coxosternum, the maximum transverse
width between the lateral sides. To cope with possible allo-
metric growth and interindividual variability, measures
were taken, whenever possible, from series of conspecific
specimens. Within mecistocephalids, three intervals were
tentatively recognized. In all lithobiomorphs, scolopendro-
morphs and Adesmata, forcipules are typically stout with
respect to body width.
88. Forcipular segment, trochanteropraefemur, proximal
tooth: (0) virtually absent; (1) present.
In all mecistocephalids, a weak incomplete sutural line
runs on the internal side of the trochanteropraefemur, prob-
ably marking the ancestral joint between two separate arti-
cles. In some species, a sclerotized tooth (here called the
proximal tooth) develops just proximal to the sutural line
(Fig. 12C). The proximal tooth is usually reduced compared
with the distal tooth (see ch. 89), although it exhibits con-
spicuous intraspecific variability. In some species, however,
it is virtually absent and the internal surface is only slightly
swollen (Fig. 12B). Lithobiomorphs, scolopendromorphs
and Adesmata do not have proximal teeth.
89. Forcipular segment, trochanteropraefemur, distal tooth:
(0) virtually absent; (1) present.
In all mecistocephalid species, the trochanteropraefemur
bears a distal tooth, which emerges at the end of the internal
side of the corresponding article (Fig. 12A). It is usually the
most conspicuous tooth of the forcipule. In lithobiomorphs,
the trochanteropraefemur always lacks teeth, whereas in
scolopendromorphs a distal tooth is sometimes present.
The pattern is more diverse in Adesmata.
90. Forcipular segment, articulation between trochantero-
praefemur and tarsungulum: (0) absent; (1) present.
In most Epimorpha (except for some Cryptops; Borucki,
1996), the trochanteropraefemur and the tarsungulum of
each forcipule are directly articulated by means of a scler-
otized hinge on the external side (Fig. 12). The intermediate
articles, i.e. the femur and the tibia, are thus incomplete. In
all other centipede groups, the trochanteropraefemur and
the tarsungulum are never directly in touch. This feature
has long been recognized as a synapomorphy of Epimorpha
(see, e.g. Dohle, 1985; Borucki, 1996).
91. Forcipular segment, tibia, tooth: (0) virtually absent;
(1) present.
In most mecistocephalid species, a sclerotized tooth is
present on the internal side of the third article of the for-
cipule (Fig. 12B). It is usually small and variable in size.
Thus, its occurrence was checked, whenever possible, in
series of conspecific specimens. In lithobiomorphs, scolo-
pendromorphs and Adesmata, the forcipular tibia is always
devoid of teeth.
92. Forcipular segment, tarsungulum, teeth: (0) none; (1) 1;
(2) 2, dorsal and ventral, respectively.
In all mecistocephalids, the forcipular tarsungulum is
typically swollen at the base of the internal side. In some
species, one or two sclerotized teeth emerge at this level
(Fig. 12C). These teeth are usually tiny compared with
other forcipular teeth, but intraspecific differences occur.
No teeth are present on the forcipular tarsungulum of
lithobiomorphs and scolopendromorphs. In Adesmata, the
condition is diverse.
93. Forcipular segment, calyx: (0) reaching the intermediate
articles only; (1) reaching the distal part of the
trochanteropraefemur; (2) reaching the trochantero-
praefemur mid-length.
In all centipedes, a channel runs inside the forcipule from
the poison gland to the tarsungulum, where it opens on the
external side close to the tip. The innermost part of this
channel, bearing short secondary channels, is called the poi-
son calyx. In mecistocephalids, the calyx is very elongate,
uniformly wide but not perfectly straight (Fig. 12). In most
species, it ends at the level of the distal part of the trochan-
teropraefemur. In a few species it is shorter, reaching the
intermediate articles only. In other species, it deepens to the
mid-length of the trochanteropraefemur. Slight variation
also occurs among conspecifics. This character was evaluated
by observing the forcipules from above in adequately cleared
specimens. In lithobiomorphs, the calyx is quite deep,
whereas in scolopendromorphs it is similar to most mecisto-
cephalids. In most Adesmata, it does not overreach the
intermediate articles (Foddai & Minelli, 2000).
572 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Leg-bearing trunk
94. Leg-bearing trunk, segments: (0) heteronomous;
(1) homonomous.
All geophilomorphs are characterized by a homonomous
leg-bearing trunk: segments are very similar to one another,
with the exception of the forcipular segment and the ter-
minal ones. Morphological changes along the body axis are
gradual and a mid-length transition or anomaly is detect-
able in some groups only (Demange, 1963; Minelli et al.,
2000). In all lithobiomorphs and scolopendromorphs, a
homonomous pattern is present only on the ventral side of
the trunk, whereas lateral and dorsal sides are characterized by
a heteronomous pattern involving tracheal spiracles and terga.
95. Leg-bearing trunk, praetergum: (0) absent; (1) present.
In all geophilomorphs, each segment is covered by two
dorsal sclerites and the anterior one (praetergum) is shorter
than the posterior one (tergum). In both lithobiomorphs
and scolopendromorphs, each segment is covered by only
one sclerite (tergum); transverse lines actually separate a
shorter anterior part from a longer posterior part, but this
pattern is probably not homologous to that of geophilo-
morphs (see Eason, 1964 vs Lewis, 1981).
96. Leg-bearing trunk, praesternum: (0) absent; (1) present.
In all Epimorpha, the main ventral sclerite (sternum) of
each leg-bearing segment is accompanied by an anterior
sclerite (praesternum), which is shorter than the sternum
and is often reduced to two separate paired elements. Only
the first leg-bearing segment lacks a praesternum. Praes-
terna and sterna are traditionally considered different scler-
ites, but their actual separation has been questioned (Fusco
& Minelli, 2000b). Mecistocephalus microporus has long
been considered as lacking the praesternum of the last leg-
bearing segment (Attems, 1928, 1947; Wang, 1951; Crabill,
1964), but our observations proved this is not true (Bonato
et al., 2001). In lithobiomorphs, praesterna are not recognizable.
97. Leg-bearing trunk, tracheae, longitudinal anastomoses:
(0) absent; (1) present.
In all Epimorpha, the tracheae of each leg-bearing seg-
ment are fused to those of other segments, producing inter-
segmental anastomoses or, at least, intersegmental bridges
between adjacent stigmata of the same side (Fuller, 1960;
Manton, 1965). In lithobiomorphs, tracheae of different
segments do not match. This feature was checked by obser-
ving cleared specimens from the dorsal side.
98. Leg-bearing trunk, tracheae, transverse anastomoses:
(0) absent; (1) present.
In all geophilomorphs, right and left tracheae anasto-
mose within each leg-bearing segment (Fuller, 1960;
Manton, 1965; Minelli, 1985). Similar anastomoses are not
present in lithobiomorphs and are rare in scolopendro-
morphs. This feature was checked by observing cleared
specimens from the dorsal side.
99. Leg-bearing trunk, sternum, endosternal process:
(0) absent; (1) present.
In all mecistocephalids, each sternum of the trunk has a
tongue-shaped posterior process, completely covered by the
following sternum and usually called the endosternal pro-
cess (Brolemann, 1930). The endosternal processes are more
extended in the anterior part of the trunk, gradually
decrease in length towards the posterior part and com-
pletely fade at about mid-length of the trunk. These pro-
cesses were observed through the integument in adequately
cleared specimens. Endosternal processes are absent in
lithobiomorphs, most scolopendromorphs and all Adesmata.
In cryptopids, similar processes are possibly homologous to
the endosternal processes of mecistocephalids. Worth notice
are similar processes in the extinct devonobiomorphs, basal
to scolopendromorphs (Shear & Bonamo, 1988).
100. Leg-bearing trunk, sternum, sternal apodema and mid-
longitudinal sulcus: (0) absent; (1) present.
In all mecistocephalids, the sternum of each leg-bearing
segment is thickened along a mid-longitudinal line, corres-
ponding to an internal projection which extends from about
the mid-length of the sternum to the end of the endosternal
process. This structure is called the sternal apodema or
rhachis (Crabill, 1959, 1964, 1970). The external surface of
the sternum is enfolded in correspondence to the apodema,
forming a mid-longitudinal sulcus, visible under incident
light. No such feature is known in the other centipede
groups, although the longitudinal thickenings or furrows
found on the sternal surface in some Strigamia species
(Geophilomorpha: Linotaeniidae), would be worth closer
attention, as would the possibly homologous sulci found in
Cryptops, which are, however, very weak and do not reach
the posterior margins of the sterna.
101. Leg-bearing trunk, sternum, mid-longitudinal sulcus:
(1) not furcate; (2) furcate.
In some mecistocephalid species, the mid-longitudinal
sulcus of each sternum divides forwards into two short
diverging branches. This bifurcation is more evident in the
most anterior segments, fading gradually towards the pos-
terior part of the trunk. The width of the angle between the
two branches gradually changes along the trunk. The occur-
rence of this bifurcation was checked under incident light.
This character does not apply to the outgroup taxa, because
they lack a mid-longitudinal sulcus. The presence vs
absence of the bifurcation has long been used as an
important taxonomic character in mecistocephalids, but
some inconsistencies appeared in the literature. For
instance, all Tygarrup species have a weak bifurcation, but
different authors describe it as either completely absent
(in most species), only shortly branched (in Tygarrup
takarazimensis; seeMiyosi, 1957; Titova, 1965, 1975) or evident
(in Tygarrup intermedius Chamberlin, 1914; see Chamberlin,
1914). Furthermore, some Tygarrup specimens were erro-
neously identified as belonging to Mecistocephalus (see, e.g.
Pocock, 1891; Silvestri, 1895, 1919; Attems, 1907).
102. Leg-bearing trunk, sternum, pore field: (0) absent;
(1) present.
In most mecistocephalids, the sterna of the trunk are not
pierced by the usual sternal pores found in most geophilo-
morphs. Only males (but not females) of some species of
Tygarrup have pores, grouped into pairs of lateral elliptical
fields which decrease in area towards the posterior part of
the trunk (Verhoeff, 1942; Titova, 1983). No sternal pores
Evolution of segment number in Mecistocephalidae 573
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occur in lithobiomorphs, scolopendromorphs and neogeo-
philid geophilomorphs. Most of the other groups of Ades-
mata are characterized by peculiar pore fields, without any
sexual difference. These pores are the openings of glands
which produce sticky secretions and cyanide derivatives
(Hopkin & Gaywood, 1987; Hopkin et al., 1990; Hopkin
& Anger, 1992; Turcato et al., 1995). These products are
thought to repulse predators and parasitic micro-organisms.
The homology between the male pore fields of Tygarrup and
those of most geophilomorphs is dubious (Foddai & Minelli,
2000; Bonato & Minelli, 2002). Until now, pores were
recorded in only two species of Tygarrup, i.e. T. poriger
from the Himalayas and T. javanicus originally described
from Java (Verhoeff, 1942; Crabill, 1968).
103. Leg-bearing trunk, leg, tarsus: (0) divided into 2
articles; (1) undivided.
In all mecistocephalids, the telopodite of all the legs,
except the last pair, is invariably composed of five articles
(trochanter, praefemur, femur, tibia and tarsus) and ends
with a sclerotized claw. The same condition is found in all
other geophilomorphs. In many lithobiomorphs (but not in
Monotarsobius and various Henicopidae), the telopodite
comprises six articles, with two articles (tarsus I and tarsus
II) corresponding to the single tarsus of geophilomorphs.
Scolopendromorphs are characterized by a pattern of arti-
cles similar to that of geophilomorphs, but an independent
trochanter is not detectable and the legs of the penultimate
pair have two tarsal segments, in Cryptops at least.
104. Leg-bearing trunk, ratio of leg I to leg II length:
(0) 0.7–0.9; (1) 0.3–0.6.
In all mecistocephalid species, the first pair of legs is
shorter and more slender than the following legs, but two
degrees of size reduction can be distinguished. This was
estimated as the ratio between the length of the telopodite
of the first pair and that of the second pair. This ratio
ranges from 0.3, e.g. in Mecistocephalus angusticeps, to
0.9, e.g. in Mecistocephalus satumensis Takakuwa, 1938
[according to Ribaut (1914) and Takakuwa (1938), respect-
ively]. In lithobiomorphs, scolopendromorphs and Ades-
mata, the first pair of legs is always smaller than the
following pair, but the difference is not so consistent as in
most mecistocephalids.
Last leg-bearing segment
105. Last leg-bearing segment, sternum, lateral notches:
(0) absent; (1) present.
In some mecistocephalid species, the sternum of the last
leg-bearing segment is characterized by a pair of weak con-
strictions, at about mid-length of the lateral margins
(Fig. 13C). These notches are variably marked among con-
specific individuals and anomalous specimens occur. In other
mecistocephalids, as well as in the other centipede groups, the
last sternum is usually shaped as a simple shield, e.g. tri-
angular or trapeziform, without any lateral notch (Fig. 13B).
106. Last leg-bearing segment, sternum, pillowlike posterior
process: (0) absent; (1) present.
In some mecistocephalid species, the sternum of the last
leg-bearing segment appears as a simple shield, with a regu-
larly curved posterior margin (Fig. 13B). In other species,
the sternum has a short pillowlike posterior projection
(Fig. 13A). The relative size of this process is affected by
both inter- and intraspecific variation and anomalous speci-
mens occur. Thus, this character was checked, whenever
possible, in series of conspecific specimens. In lithobio-
morphs, scolopendromorphs and Adesmata, the last ster-
num is usually simple, without a posterior process.
107. Last leg-bearing segment, sternum: (0) not constricted
by the coxopleura; (1) constricted by the coxopleura.
In a few mecistocephalid species, the sternum of the last
leg-bearing segment is peculiarly elongate and constricted
between the coxopleura, so that the lateral margins are
concave rather than convex. In all other centipede groups,
no similar shape occurs. Different authors described this
shape in different ways, thus failing to recognize the actual
similarity among some species [cf. the illustrations ofMecis-
tocephalus diversisternus, M. mirandus, M. takakuwai and
M. smithii by Silvestri (1919), Verhoeff (1934), Takakuwa
(1940) and Takashima & Shinohara (1952)].
108. Last leg-bearing segment, posterior part of the sternum
and internal part of the coxopleura, thick pilosity:
(0) absent; (1) present.
In all mecistocephalids, short and dense setae cover the
posterior part of the sternum and the postero-internal parts
of the coxopleura, on the ventral side of the last leg-bearing
segment (Fig. 13). These setae become gradually longer and
less dense towards the anterior part of the sternum and
towards the lateral parts of the coxopleura. The condition
is usually similar in males and females. Although the
setae increase in number during growth, the thick pilosity
is already visible in juveniles. In lithobiomorphs, scolo-
pendromorphs and Adesmata, no differentiated area is
recognizable.
109. Last leg-bearing segment, coxopleuron, coxal pores on
the dorsal surface: (0) absent; (1) present.
The coxal pores are the external openings of peculiar
organs placed inside the coxopleura (Fig. 13). The anatomy
and function of these organs were not investigated in mecis-
tocephalids, but they most probably play a function in
water balance, as in lithobiomorphs, scolopendromorphs
and Adesmata (Rosenberg, 1982, 1983a,b; Littlewood,
1983; Rosenberg & Bajorat, 1984). In most mecistocephalid
species, the coxal organs open on the ventral and lateral
sides of each coxopleuron. Only in a few species do some
pores open on the dorsal side as well. The number and area
covered by coxal pores increase during growth. Thus, the
pattern was evaluated in adult specimens. In lithobio-
morphs and scolopendromorphs, the coxal pores are ven-
tral and lateral only, whereas in Adesmata the distribution
patterns are very diverse.
110. Last leg-bearing segment, coxopleuron, macropore:
(0) absent; (1) present.
Mecistocephalid species differ in the adult pattern of
coxal pores, in terms of number, size and position. These
differences correspond to differences in the developmental
574 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
schedule of the pores. In some species, juveniles hatch with
no pores, but they soon develop a set of similar pores on
each coxopleuron. In a few species, however, one large pore
(macropore) develops before all other pores and remains
recognizable as the largest one throughout growth
(Fig. 13A). This pattern was well studied in Dicellophilus
carniolensis (Verhoeff, 1902–1925). There are no sexual dif-
ferences. The occurrence of this developmental pattern was
evaluated by observing either juveniles (in which the macro-
pore is more conspicuous) or grown individuals (in which
the macropore may be distinguished from the other pores).
A similar developmental pattern is unknown in lithobio-
morphs, scolopendromorphs and Adesmata.
111. Length ratio of last leg to penultimate leg: (0) 1.2–2.0;
(1) 2.2–3.0.
In all mecistocephalid species, the telopodites of the last
pair of legs are longer than those of all other legs, but to a
different degree. The length ratio between the last and the
penultimate legs was taken as a measure of relative elonga-
tion. Sexual dimorphism in the last pair of legs, when pre-
sent, does not affect this ratio.
112. Last leg: (0) as slender in males as in females;
(1) swollen in males, slender in females.
The legs of the last pair are similar in both sexes in some
species of mecistocephalids, but are evidently swollen in the
males of other species. This sexual dimorphism is even
A B C
Fig. 13. Last leg-bearing segment and terminal segments (ventral view) of some mecistocephalids. Only the left telopodite is illustrated. Setae
on the right coxopleuron and on the terminal segments are omitted. A, Dicellophilus latifrons, /, subadult, Honshu; B, Tygarrup
muminabadicus, /, subadult, Kashmir; C, Mecistocephalus punctifrons, /, subadult, India. Scales¼ 0.5mm.
Evolution of segment number in Mecistocephalidae 575
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
stronger in many Adesmata, the last legs differing some-
times in both width and structure.
113. Last leg, short setae: (0) absent; (1) present.
In some mecistocephalid species, some short but strong
setae are interspersed among the common setae on the
telopodites of the last pair of legs, particularly on the ven-
tral side (Fig. 13A). In these species, short setae are present
in all individuals, but their density may be affected by age
and sex. Similar setae are also present in scolopendro-
morphs and Adesmata, at least in the species considered
here as outgroups, but are absent in lithobiomorphs, even
though short sensilla occur in the same position.
114. Last leg, short setae: (0) as dense in males as in
females; (1) more dense in males than in females.
In mecistocephalid species bearing short setae on the last
pair of legs (see ch. 113), the pattern of these setae may be
either similar or different in the two sexes. When sexual
dimorphism occurs, the short setae are more numerous
and dense in males than in females. This character does
not apply to species lacking short setae. The pattern of
setae is often sexually dimorphic in Adesmata, but not in
scolopendromorphs.
115. Last leg, praetarsus: (0) a well-developed claw; (1) a
group of short spines; (2) 1 short slender spine;
(3) none.
In most mecistocephalid species, the legs of the last pair
bear a short and slender spine on the tip. This spine is
usually interpreted as homologous with the claws of the
other legs and the well-developed praetarsus of the last
pair of legs in other centipedes. The spine may not be
detected in all specimens of a given species. In other mecis-
tocephalids, the praetarsus is represented by a stout
rounded tubercle, crowned by small spines. In some other
species, no spine or tubercle is present. Because of the large
interindividual variation, we examined this feature, when-
ever possible, in many specimens of each species. In all
lithobiomorphs and most scolopendromorphs and Ades-
mata, the praetarsus of the last legs is a well-developed
claw. In some scolopendromorphs and Adesmata, however,
it is either reduced or absent.
Terminal segments
116. Genital segment, female gonopods: (0) of 3 articles,
with claws; (1) of 2 articles, without claws.
In all adult mecistocephalids, gonopods are short two-
article appendages (Fig. 13). Male gonopods are slender and
well separated, whereas female gonopods are subtriangular
and usually in touch. Gonopods of females, in particular,
are undeveloped in the first juvenile stages, and have only
one article when they first appear. Female gonopods are
variable in Adesmata: for instance, a pair of two-article
gonopods similar to those of mecistocephalids are present
in the himantariids, whereas only a very rudimentary struc-
ture is present in geophilids. In all lithobiomorphs, the
female gonopods are well-developed three-article appen-
dages with accessory spurs. In scolopendromorphs, these
appendages are virtually absent. From the literature, it is
apparent that developmental changes were often over-
looked, so that the gonopods of mecistocephalid females
were erroneously assumed to be separated in some species
and in contact in other species, and either of one or two
articles (see, e.g., Haase, 1887; Attems, 1929; Verhoeff,
1937, 1939; Lewis, 1991).
Number of segments
117. Number of leg-bearing segments, interindividual vari-
ation at adult stage: (0) absent; (1) present.
In most mecistocephalid species, the number of leg-bear-
ing segments is the same in all specimens, without any age-
or sex-related variation. The number, however, may be
different in different species (see Introduction). To date,
interindividual variation is known only in Mecistocephalus
microporus, where the number of leg-bearing segments
ranges from ninety-three to 101 at least (Bonato et al.,
2001). However, this character has been coded as unknown
for species known from one specimen only, either directly
observed by ourselves or recorded in the literature. Intra-
specific variation in the adult stage is unknown in lithobio-
morphs and scolopendromorphs, whereas it is documented
in most Adesmata and it is supposed to be a common
features of this latter group.
118. Number of leg-bearing segments, number at adult stage:
(0) 15; (a) 21; (b) 41; (c) 43; (d) 45; (e) 47; (f) 49; (g) 51;
(h) 53; (i) 57; (j) 59; (k) 63; (l) 65; (m) 93–101;
(n) 43–47; (o) 83–111.
Different codes have been assigned to all different numbers
of leg-bearing segments recorded in the species considered.
For species with intraspecific variation (see ch. 117), different
codes have been assigned to different ranges of variation.
576 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Appendix
2.Data
matrix
forthecladisticanalysis.
Specieswereenteredin
random
order.Speciesnames
correspondto
those
inTable
1.Character
numberscorrespondto
those
inAppendix
1.Plesiomorphic
statesare
coded
as’0’;
unknownstatesare
indicatedbyaquestionmark
(?).Whereacharacter
wasim
possible
todefineordoes
notapply
toaspecies,itisindicatedbyadash
(-).Characters117and118are
relatedto
segmentationandwereusedasoptionalin
ouranalyses(see
Materialsandmethods).
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111111
0000000001111111111222222222233333333334444444444555555555566666666667777777777888888888899999999990000000000111111111
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678
Lithobiusforficatus
000–00000000000000–00–00?000000000––000000000??000000000000000000–0000000000000000000000000000000000–000000000000–0000
Krateraspismeinerti
011?11??1000?1111112130030?01120011100001011130?120001111??3101111102000?2??10?00?1??200111?11111111101?000100?????10d
Arrupdentatus
011211111000111111111122300011300131000010111100110011111011100011001100011000000010020011111111111110100001000010210b
Mecistocephalussp.A
0112110110000111111112003001113011120000101111001310010112021011111020000211100000100011111211111111101?0101000?0–210e
Cryptopsanomalans
001–2100001–111000–00–00?010000000––000001000??000000102000000000–00–0000–––000100000200010010011010–01000000000100–0a
Mecistocephalussp.B
?11111010000011111111200300111301112000010111200131101011001102111102000021111000011131111121111111110110101000?1??10g
Dicellophilusanomalus
011111011002111111100222201011200121101001111201120001021113100111001010121010000111010011121111111110100101010111110b
Tygarrupsp.A
01121111100001111110021130001120011100001011120012000101100210111100200002101100001002001110111111111111000100000–210c
Mec.(M
.)angusticeps
111?11?1100001111111120030?1113011120000101113001310010212?2101111102000021110?00?1??011111??111111110110101000?0–210e
Krateraspissselivanovi
011?11??1000?1111112130030?01120011100001011130?120001021??310111110200002??1??00?1??200111?11111111101?000100?0???1?h
Mec.(M
.)guildingii
0112110?000001111111120030011130111?0000?01112001311010210?210111110200002111??00?1??321111?011111112010010110010–210f
Dicellophiluslatifrons
011111011000111111100222101011200121101001111201110001021112100111001010121010000111010011121111111110100001010111110b
Mecistocephalussp.C
0111110100000111112112003011113011120000001114001311010111021021121020001221110000111011111111111111201?0101101?1?21?h
Geophilusinsculptus
01111111101–111100–00–00?000000000––0000111?100000101000000000010–0001000100000110000100010101111100–11000000001110–1n
Mec.(P.)superior
111?11??10000111111112003??111??111201000?1114001211010010?210211210200002??10?00?1??011111??1111111201?01011010???10f
Tygarruptakarazimensis
011111112000011111100211300011200111000010111300130001011002101111002000021011000010020011101111111110110001000?0–210d
Mec.(M
.)conspicuus
1111110?100001111111120030?1113011120000101112001311010111?210111110200002?110?00?1??211111??11111111011010100?????10f
Arrupholstii
011211011000111111111122300011300131000010111300120011111011101011011101011000000010020011112111111110110001100011210b
Mec.(M
.)diversisternus
01111101000101111112122131011130011200000011130013110112110210211110200002211110011103211111111111111011001100001?21?i
Mec.(M
.)itayai
111111??100101111112120030?1113011121000101113001311011211?210211110200002??10?00?1????11112?1111111201?00?1?0?????10f
Anarrupnesiotes
011111??1100111111100221?0?0111??1?100?0??1113101210010110?211110–002000121010000?1??100111??1111111201?0001?001???10b
Mecistocephalusjaponicus
01111101000101110112122131011130011100000111130013110112111310211110200002111010011100211110111111111010001110001031?k
Mec.(B.)mirandus
01111101000101110112122131011130011200000111130013110112111310211110200002211010011100211100111111111010001110001?31?l
Proterotaiwanella
sculptulata
011111??10001111111111023100112001?10001101113011?0001??1???10?1110?2?0002?0??00001????01110?111111110100001000????10f
Evolution of segment number in Mecistocephalidae 577
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Appendix
2.Continued.
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001111111111111111111
0000000001111111111222222222233333333334444444444555555555566666666667777777777888888888899999999990000000000111111111
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678
Mec.(F.)longichilatus
011111??10??01111111120010?11100111?000010111100131?011310?410111110200002??1??00??????1111??1111111101???01000????10f
Mec.(M
.)modestus
111111111000011111111200300111301112000010111100131101011002101111102000021111000010000111120111111110110101000011210f
Mec.(M
.)multidentatus
011111010000011111211200300111301112000000111300131101021003102112102000021111000001101111111111111120111101101010210f
Mec.(M
.)nannocornis
011111010000011111111200310111301112000010111300131001011202100111102000021111000010020111121111111110110101000010210d
Mecistocephalusbenoiti
111111000000011111211200301111201112000000111300131101011201102112102010021111000011101111122111111120110101000010210f
Agnostruppaucipes
011?11??00001111111112023000112001410000101112011300011212?21021111111010??0??00001??2001101?1111111101?000100?????1?b
Mec.(M
.)tahitiensis
01111101100001111111120031011130111200001011110013100101120210111210200002111100001000011112111111111011010100000–210e
Dicellophiluscarniolensis
011111011100111101100222101011200121101001111101110001001002101111001000121010000011010011111111111110100001010111110c
Mec.(M
.)takakuwai
01111101000101111112120131011130011200000011130013100112110210211110200002111010011103211112111111111011001100101031?j
Mec.(M
.)punctifrons
111111000000011111211200301111311112000000111300121101021202102112102000021110000011101111121111111120110101100010210f
Tygarrupmuminabadicus
11111111210101111110021130001120011100001011130012000101100210111100200002101100001002001110111111111110000100000–210d
Mec.(M
.)mikado
11111101100001111121120030111121111200000011130012110101100210111210200002111000001110011112111111111011110110100–210f
Mecistocephalusmicroporus
01111100000001111111120031111130111200001011130012110102100310211210200002111110001110211111111111112011100110100–211m
Nannarruphoffmani
01121101001–1111111111023000113001?10000??11110?1100011110?110111101110101?00000001002001101111111111010000100001?210b
Stigmatogaster
gracilis
111111110000111100–00–2??000000110––0000101103000000101100?000210–0001100000000110000100110011111100–1100000100111211o
Sundarrupflavipes
011111011100111111100221?0101111112100101011131012100101100211110–002000121010000001010011122111111110110001100?1?110b
Proterotaiwanella
tanabei
01111101101–111111111102310011300131000110111301120001011002102111012000020110000111001011100111111110100001000?1?11?d
Mec.(D
.)subgigas
1111110110000111112112003101112111220100011114101311010111021021121020001211110000111011111??11111112010010111001?210f
Takashim
aia
ramungula
0111110120001111011002003111113001?1000010111300120001011202101111102000021110100111020011101111111110110001000011210d
Dicellophiluslimatus
011111011002111111100222201011200121101001111101120001021112100111001010121010000111010011121111111110100001010111110d
Tygarrupjavanicus
01121111200001111110020131001120012100001011130012000101100210111100200002100100001002001110111111111111000100000–210d
Mecistocephaluslongiceps
011?11??00000111111112003??111?011?20000101113001?1?01??1???10?11?10200002??1??00?1??3211112?11111112011??01?0?0??21?f
Mec.(M
.)lifuensis
011?11??000001111111120030?1112011120000101112001311010210?210111110200002??1??00?1??011111??111111120110?01?0?0??210g
Arruppylorus
011211??100011111111112230?0113001?10000101111001200111110?110101100110101?0???00?1??2001111?1111111101000010000???10b
Mec.(M
.)spissus
011211010000011111111200301111301112000010111200131001011202101112102000021111000?1002011111?1111111101101010000??210d
Tygarrupanepipe
011211??10000111111002?13??0112001?1000010111?001200010?10??10?11100200002????000?1????0110??11111111?1?00010000??210d
578 L. Bonato et al.
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
Appendix 3. Main synapomorphies supporting the clades of the phylogenetic trees.
Relevant characters and state transitions are indicated for each clade. Clade numbers correspond to those plotted on the trees
(Figs 2 and 3). Character number and state codes correspond to those in Appendix 1.
Clade Character: state changes
1 3: 0!1 15: 0!1 90: 0!1 96: 0!1 103: 0!1
2 2: 0!1 16: 0!1 94: 0!1 95: 0!1
3 102: 0!1 117: 0!1
4 18: 0!1 29: 0!1 30: 0!1 34: 0!1 49: 0!1 69: 0!1 100: 0!1
5 70: 0!1 72: 0!1
6 22: 2!1 31: 2!3
7 53: 0!1 64: 1!0
8 68: 1!0
9 74: 1!2
10 115: 2!1
11 22: 2!1 40: 0!1
12 23: 0!2 27: 0!1 35: 3!2 39: 0!1 73: 0!1
13 24: 2!1 31: 2!1 47: 0!1 48: 1!0 51: 0!1 62: 0!1 65: 1!0
14 37: 0!1 41: 1!0 42: 0!1 110: 0!1
15 58: 0!1 59: 0!1 71: 0!1 82: 0!1
16 12: 0!2 25: 1!2
17 13: 1!0 24: 2!1 35: 3!1 48: 1!0
18 7: 0!1 9: 1!2 23: 0!1 78: 0!1
19 102: 0!1
20 4: 1!2
21 9: 2!1
22 67: 0!1 76: 0!1
23 22: 2!3 60: 2!3
24 28: 0!1 31: 2!3
25 20: 0!1 33: 0!1 36: 1!2 50: 2!3 51: 0!1 88: 0!1 106: 0!1
26 9: 1!0
27 86: 2!0
28 113: 1!0
29 –
30 –
31 1: 0!1
32 –
33 – -
34 84: 0!1
35 9: 1!0
36 56: 1!2
37 –
38 46: 2!3
39 12: 0!1 20: 1!2
40 23: 0!2 24: 0!1 26: 0!1 33: 1!0
41 115: 2!3
42 17: 1!0 42: 0!1 59: 0!1 60: 2!3 92: 2!0 109: 0!1
43 78: 0!1 85: 0!1
44 –
45 –
46 19: 1!2 27: 0!1 41: 1!0 66: 1!2
47 109: 0!1
48 1: 1!0
49 60: 2!3 105: 0!1
50 32: 0!1
51 –
52 38: 0!1 46: 3!4
Evolution of segment number in Mecistocephalidae 579
# 2003 The Royal Entomological Society, Systematic Entomology, 28, 539–579
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