A NEW BASAL BALAENOPTERID WHALE FROM THE

PLIOCENE OF NORTHERN ITALY

by MICHELANGELO BISCONTIDipartimento di Scienze della Terra, Universita di Pisa, via Santa Maria 53, 56126 Pisa, Italia; e-mail: bisconti@dst.unipi.it

Typescript received 27 April 2006; accepted in revised form 13 September 2006

Abstract: A new basal balaenopterid genus and species,

Archaebalaenoptera castriarquati, is described and compared

with all the living and fossil members of the family Balae-

nopteridae and related fossil rorqual-like taxa. It was found

in the Lower Pliocene of northern Italy, and is characterized

by a supraoccipital with a transversely compressed anterior

process, the zygomatic process of the squamosal diverging

from the longitudinal axis of the skull, very long nasal bones,

and subtle exposition of the parietal on the dorsal wall of the

skull. It is primitive in having a maxilla with a long ascend-

ing process that is posteriorly unexpanded and round, and a

dentary that is straight and not bowed outward, unlike that

of living Balaenopteridae. In particular, the discovery of this

new genus suggests that, among the early members of Balae-

nopteridae, the acquisition of the typical sutural pattern

shown by maxilla, frontal, parietal and supraoccipital pre-

ceded the acquisition of the feeding-related traits that are

characteristic of the family. The primitive morphology of the

feeding-related structures of A. castriarquati (i.e. the straight

dentary and the flat glenoid fossa of the squamosal) suggests

that this whale was unable to undertake the intermittent ram

feeding typical of Balaenopteridae as efficiently as living

members of the family.

Key words: Balaenopteridae, Cetacea, Italy, Mysticeti, phy-

logeny, Pliocene, skull morphology.

The origin and early radiation of the family Balaenop-

teridae (including rorqual and humpback whales) is not

yet completely understood. Descriptions of several ror-

qual-like taxa from Europe and the eastern United States

were published during the second half of the nineteenth

century by van Beneden (1882) and Cope (1868, 1872,

1895). A few accounts also appeared during the twentieth

century. Among these, papers written by Japanese, Ameri-

can and Italian workers documented the presence of taxa

closer to the genera Balaenoptera and Megaptera in Late

Miocene and Pliocene sediments of Pacific, Atlantic and

Mediterranean basins (e.g. True 1912; Kellogg 1922;

Caretto 1970; Oishi et al. 1985; Demere 1986; Pilleri

1989; Sarti and Gasparri 1996).

Zeigler et al. (1997) published the first cladistic analy-

sis of Balaenopteridae; however, their study was not

assisted by a computer program; they suggested that the

problematic ‘Plesiocetus’ cortesii was the sister taxon of

the Balaenopteridae including the archaic Parabalaenop-

tera baulinensis and the modern subfamilies Balaenopter-

inae (rorquals) and Megapterinae (humpbacks). In that

paper, ‘P.’ cortesii was represented by the Mount Pulg-

nasco whale of Cortesi (1819), which had also been des-

cribed by van Beneden (1875) and Strobel (1881).

‘Plesiocetus’ cortesii is a Late Pliocene Mediterranean

taxon whose cranial morphology is intermediate between

the problematic cetotheres (Cetotheriidae sensu Sanders

and Barnes 2002) and the balaenopterids; in fact, it

shares with cetotheres the triangular and pointed anter-

ior end of the supraoccipital, transversely narrow inter-

orbital region of the frontal, and straight dentary. On

the other hand, it shares with balaenopterids the long

ascending process of the maxilla, a wide supraorbital

process of the frontal that is abruptly depressed from

the interorbital region of the frontal, and a superimposi-

tion of the parietal on the emergence of the supraorbital

process of the frontal so that the anterior border of the

parietal is anterior to the posteromedial corner of the

maxilla. A computer-assisted cladistic analysis of Balae-

nopteridae was provided by Demere et al. (2005; see

‘Discussion’).

Several fossil rorqual-like mysticetes have been found

in Late Miocene and Pliocene deposits of northern Italy.

Some of these are representatives of the earliest phases of

the morphological transformations that led to modern

balaenopterids (see Bisconti 2003a). In this paper, a

new early-diverging balaenopterid genus and species,

Archaebalaenoptera castriarquati, is described based on a

[Palaeontology, Vol. 50, Part 5, 2007, pp. 1103–1122]

ª The Palaeontological Association doi: 10.1111/j.1475-4983.2007.00696.x 1103

fairly complete skull from the Lower Pliocene Castell’Arq-

uato Formation of northern Italy.

The skull was found in 1983 by Roberto Volpi, Piero

Rusconi and Luigi Rusconi in the Carbonari River

erosion system near the village of Tabiano di Lugag-

nano (Text-fig. 1). It was collected through the joint

effort of the Museo Geopalaeontologico ‘Giuseppe Cor-

tesi’ of Castell’Arquato, the Istituto di Palaeontologia of

the University of Modena, the Gruppo Palaeontologico

‘La Xenophora’ and the Gruppo Palaeontologico e Min-

eralogico of Piacenza. The operations related to the dig-

ging and preparation of the skull were described by

Francou (1994). The skull is housed in the Museo Geo-

palaeontologico ‘Giuseppe Cortesi’ in the town of Cas-

tell’Arquato.

Institutional abbreviations. AMNH, American Museum of Nat-

ural History, New York; ChM, the Charleston Museum, Charles-

ton, South Carolina; IRSN, Institute Royal des Sciences Naturelles

du Belgique, Brussels; ISAM, Iziko South Africa Museum, Cape

Town; MGB, Museo Geopalaeontologico ‘Giovanni Capellini’,

Universita di Bologna; MGPC, Museo Geopalaeontologico ‘Gius-

eppe Cortesi’, Castell’Arquato (Italy); MGPT, Museo Geopalaeon-

tologico, Universita di Torino; MPST, Museo Palaeontologico di

Salsomaggiore Terme; Salsomaggiore Terme (Italy); NMB, Natu-

ur Museum Brabant, Tilburg (the Netherlands); SBAER, Soprin-

tendenza per i Beni Archeologici dell’Emilia Romagna (Italy);

SMNS, Staatliches Museum fur Naturkunde, Stuttgart; USNM,

United States National Museum of Natural History, Smithsonian

Institution, Washington DC; ZMA, Instituut voor Systematiek en

Populatiebiologie ⁄ Zoologisch Museum, Amsterdam; ZML,

Zoologisch Museum, Leiden.

Anatomical abbreviations. apmx, ascending process of the max-

illa; cp, coronoid process of the dentary; cd, condyle of the den-

tary; cs, coronal suture; d, dentary; irfr, interorbital region of the

frontal; ip, interparietal; lc, lambdoidal crest; mx, maxilla; md,

mandibular condyle; mxf, maxillary foramina; n, nasal; nf, narial

fossa; p, parietal; pg, postglenoid process of the squamosal; pmx,

premaxilla; soc, supraoccipital shield; soct, supraoccipital tuber-

cle; sop, supraorbital process of the frontal; sq, squamosal; zp,

zygomatic process of the squamosal.

SYSTEMATIC PALAEONTOLOGY

Class MAMMALIA Linnaeus, 1758

Order CETACEA Brisson, 1762

Suborder MYSTICETI Flower, 1864

Family BALAENOPTERIDAE Gray, 1864

Genus ARCHAEBALAENOPTERA gen. nov.

Derivation of name. Greek, archaios, old, primitive; Balaenoptera,

rorqual; Archaebalaenoptera, archaic rorqual.

Type species. Archaebalaenoptera castriarquati sp. nov.

Diagnosis. Archaebalaenoptera differs from the living spe-

cies of the genus Balaenoptera in having robust tubercles

for the attachment of neck musculature in the supraoc-

cipital, very long nasal bones with a triangular interorbital

region of the frontal interposed between them posteriorly,

and a mainly straight dentary. It differs from Megaptera

novaeangliae because the supraorbital process of its fron-

tal is not directed posteriorly, the postglenoid process of

the squamosal is not much lower than the zygomatic pro-

cess of the squamosal, its nasal bones are much longer,

and its dentary is mainly straight. It differs from

‘Plesiocetus’ cortesii because the anterior border of its

supraoccipital is rounded and not pointed. It differs from

Parabalaenoptera because it has shorter nasals, a narrower

rostrum, and a mainly straight dentary.

Archaebalaenoptera castriarquati sp. nov.

Text-figures 2–5

Derivation of name. After Castell’Arquato, which is the town

where the specimen is housed.

Holotype. The Rio Carbonari skull, housed in the MGPC, Cas-

tell’Arquato, Italy. Specimen SBAER 240536. The holotype skull

is the only specimen referred to this genus and species.

A B TEXT -F IG . 1 . Maps showing the

location of the discovery site of

Archaebalaenoptera castriarquati

holotype, SBAER 240536. A, the Italian

peninsula; the area in which the

discovery was made is indicated by a

white rectangle. B, detail of the

discovery site (*).

1104 P A L A E O N T O L O G Y , V O L U M E 5 0

Horizon and locality. Rio Carbonari (Carbonari River) is

located in the proximity of Piacenza and is one of the right

tributaries of the Chero River, which it joins near the village of

Tabiano in the administrative region of Lugagnano Val d’Arda

(Text-fig. 1). The confluence area includes an important Euro-

pean Community site (SIC), ‘Castell’Arquato-Lugagnano Val

d’Arda’, and is part of the Riserva Naturale Geologica del Pia-

cenziano (Natural Geological Reserve of the Piacenzian). The

Rio Carbonari basin is superimposed onto Pliocene marine sedi-

ments, which are mainly silty and pelitic at the base and sandy

at the top. Discrete sandy levels are intercalated in the pelites in

a way that the sandy content increases incrementally from the

base to the top of the section. These sediments are clearly

exposed in erosion areas excavated on both sides of the Rio

Carbonari Basin and form a section 45 m high (Monegatti et al.

1997; Raineri pers. comm. 2005).

Abundant mollusc faunas allow for a description of palaeo-

ecological trends that took place during the deposition of the

sediments. The base of the section has circalittoral characters;

in the highest portion of the section, the mollusc assemblage

suggests that the environment changed, becoming infralittoral,

similar to a submerged beach. Abundant mollusc species

include Gigantopecten latissimus, Hinnites crispus, Spondylus

crassicosta, Circomphalus foliaceouslamellosus, Callista puella and

Paphia vetula, which, according to Monegatti and Raffi (2001),

pertain to the MPM1 mollusc unit that is older than 3Æ0 Ma.

Additional information is provided by other molluscs including

members of the families Conidae, Cypraeidae and Terebridae.

These families reached high taxonomic diversity in Mediterra-

nean during the tropical conditions of the Early Pliocene and,

according to Monegatti and Raffi (2001) and Raffi et al.

(1985), became extinct before 3Æ1 Ma. Furthermore, the gastro-

pod Gyrineum marginatum is abundant at the top of the sec-

tion but absent from the base. According to Monegatti and

Raffi (2001) and Raffi et al. (1985), its extinction coincides

with the last occurrence of Globorotalia puncticulata in the

Mediterranean, which corresponds to an age younger than

3Æ55 Ma.

The Rio Carbonari skull was discovered in the first sandy level

at a height of 18 m above the base of the section. The geograph-

ical coordinates of the discovery site are 44�50¢25¢¢N and

9�46¢52¢¢E. Based on the mollusc content, the age of the skull

can be constrained to between 3Æ55 and 3Æ1 Ma (Piacenzian,

Early Pliocene).

Diagnosis. As for genus.

Description

The holotype material consists of a well-preserved skull display-

ing a wide injury in the right temporal fossa (Text-figs 2–3).

The right side of the skull lacks the following bones: squamosal,

exoccipital, basioccipital, and posterior portion of the parietal.

Ear bones and all the postcranial bones are absent with the

exception of the posterior process of the periotic. Linear meas-

urements are provided in Table 1.

Premaxilla. The rostrum is horizontal and flat. The premaxillae

and maxillae are well preserved; the anterior apex of the left pre-

maxilla is broken. The medial border of the premaxilla parallels

the longitudinal axis of the skull; the lateral border of the pre-

maxilla widens anteriorly and its anteriormost portion is broad

(Text-fig. 3, apmx). The dorsal surface of the premaxilla is flat

A

B

TEXT -F IG . 2 . Archaebalaenoptera castriarquati holotype skull,

SBAER 240536. A, dorsal view. B, left lateral view. Scale bar

represents 150 mm.

TABLE 1 . Linear measurements (in mm) of Archaebalaenoptera

castriarquati, MGPC holotype skull; see text for explanation of

abbreviations.

Character Measurement

Condylobasal length 2160

Length of left mx (from anterior apex to

posterior end of apmx)

1542

Length of left mx (from anterior apex to

base of apmx)

1220

Length of right mx (from anterior apex to

posterior end of apmx)

1640

Length of right mx (from anterior apex to

base of apmx)

1258

Length of left pmx 1500

Length of right pmx 1520

Maximum width of rostrum anterior to

lateral process

610

Maximum width of rostrum at level of lateral

processes

810

Length of soc 450

Maximum width of soc 500

Transverse diameter of left sop 310

Anteroposterior diameter of left sop 380

Transverse diameter of right sop 350

Anteroposterior diameter of right sop 400

Maximum length of left dentary (straight) 1935

Maximum length of left dentary (curve) 1950

Maximum length of right dentary (straight) 1605

Maximum length of right dentary (curve) 1618

Height of left dentary in the anterior quarter 111

Height of left dentary at mid-length 113

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1105

anterior to the narial fossa. In the anterior half of the rostrum,

the premaxillae are divided by a 30-mm-wide space that disap-

pears approaching the narial fossa, approximately 1270 mm pos-

terior to the anterior apex of the rostrum. The maximum

transverse diameter of the narial fossa is 135 mm. Lateral to the

narial fossa, the premaxilla becomes narrower and disappears

laterally to the nasal, being superimposed by the ascending pro-

cess of the maxilla (Text-fig. 3, apmx); the posterior end of the

premaxilla is located at the middle of the supraorbital pro-

cess of the frontal (Text-fig. 3, sop). There are no premaxillary

foramina.

Maxilla. The lateral border of the maxilla is straight from the

anterior end to the lateral process. The lateral border of the

maxilla converges with the longitudinal axis of the skull, giving

the rostrum a triangular shape in dorsal view. The anterior end

of the maxilla is slightly posterior to the apex of the premaxilla.

Posteriorly, the lateral process of the maxilla is transverse to the

longitudinal axis of the skull and parallels the anterior border of

the supraorbital process of the frontal. The left maxilla bears

seven maxillary foramina and the right maxilla bears two foram-

ina (Text-fig. 3, mxf). The posteromedial corner of the maxilla

projects posteriorly into an ascending process of the maxilla,

which superimposes onto the frontal. The ascending process par-

allels the longitudinal axis of the skull and its posterior end

approaches the anterior border of the supraoccipital. Differing

from the genus Balaenoptera, the medial and lateral borders of

the ascending process of the maxilla are parallel without display-

ing the posterior transverse expansion that can be observed in

the living balaenopterines. The lateral border of the ascending

process diverges abruptly anteriorly. Ventrally, the maxilla

projects under the supraorbital process of the frontal forming an

infraorbital plate.

Nasal. The nasal is long and narrow; its posterior end does

not make contact with the anterior border of the supraoccipi-

tal (Text-fig. 3). The anterior border of the nasal is concave.

The medial borders of the nasals meet along the midline over

the anterior three-quarters of the nasal length but diverge in

the posterior quarter. The anterior border of the nasal is pos-

terior to the emergence of the ascending process of the max-

illa and lies posterior to the antorbital corner of the

supraorbital process of the frontal. The nasofrontal suture is

located well within the interorbital region of the frontal on a

transverse line crossing the postorbital corners of the supraor-

bital processes of the frontal.

Frontal. The frontal is formed by two supraorbital processes and

a small interorbital region (Text-fig. 3, irfr). The left supraorbital

process is broken medially and displaced dorsally from its ori-

ginal position. The right supraorbital process of the frontal is

broken distally; only its postorbital process is preserved. It is also

broken medially and displaced slightly ventral to its original

position.

The supraorbital process of the frontal is flat and wide; it

projects transversely from the long axis of the skull; the anter-

ior border is backward-directed whereas the posterior border

is slightly onward-directed. There is no ascending temporal

crest on the dorsal surface of the supraorbital process of the

frontal. The process is located more ventrally with respect to

the ascending process of the maxilla, which gently ascends

dorsally toward the anterior process of the supraoccipital

(skull in lateral view). In other words, the supraorbital process

of the frontal emerges abruptly from a vertical depression lat-

eral to the ascending process of the maxilla; this depression is

typical of Balaenoptera, Megaptera and Parabalaenoptera (ror-

quals and rorqual-like mysticetes) together with such problem-

atic taxa as ‘Plesiocetus’ cortesii. This depression forms a

vertical wall over the emergence of the supraorbital process of

the frontal. The anterior corner of the parietal is superim-

posed on this vertical wall and is interdigitated with the post-

eromedial corner of the maxilla. The parietal terminates at a

small protrusion emerging from the vertical wall medial to

the emergence of the supraorbital process of the frontal

(Text-fig. 4); such a protrusion has been observed in some

living balaenopterids but its occurrence is subject to individual

variation. In fact, in some individuals it may be absent but

if present (e.g. in Megaptera novaeangliae specimen SAM

ZM39781, and in Balaenoptera acutorostrata specimens SAM

ZM15269 and AMNH 35680) it always represents the anteri-

ormost point reached by the parietal. The anteroposterior

length of the supraorbital process of the frontal is comprised

in the length of the ascending process of the maxilla. There is

a gap between the posterior border of the maxilla and the

anterior edge of the supraorbital process of the frontal. The

ventral surface of the supraorbital process of the frontal can-

not be examined and described (see below).

A complex system of sutures is present between the postero-

medial elements of the rostrum (including premaxilla, maxilla

and nasal), the frontal and the parietal. The nasal bones are

located medial to the ascending processes of the maxillae and

their length is comprised within the length of the supraorbital

processes of the frontal (i.e. their anterior borders are posterior

to the antorbital corner of the frontal); the interorbital region of

the frontal is much reduced and appears dorsally as a small tri-

angular surface in between the diverging posteromedial borders

of the nasals; for this reason, the nasofrontal suture is arrow-

TEXT -F IG . 3 . Archaebalaenoptera castriarquati holotype skull.

A, dorsal view. B, left lateral view. See text for explanation of

abbreviations. Scale bar represents 150 mm.

1106 P A L A E O N T O L O G Y , V O L U M E 5 0

shaped with an anterior apex (Text-fig. 5). The interfrontal

suture is not fused. The coronal suture is evident in lateral view

between frontal and parietal on the vertical wall over the emer-

gence of the supraorbital process of the frontal, and is curved

with anterior convexity.

Lacrimal. The lacrimals are located between the infraorbital pro-

cesses of the maxillae and the anterior borders of the supraorbit-

al processes of the frontal. They are transverse to the long axis

of the skull, have a rectangular form, and are located in the gap

between the maxilla and the frontal slightly ventral to the antor-

bital corner of the supraorbital process of the frontal. No ana-

tomical formations are detectable on these bones.

Parietal. The parietal is observed dorsal and medial to the

supraorbital process of the frontal and on the medial wall of the

temporal fossa anterior to the squamosal (skull in lateral view).

Its anterior process is anterior to the posteromedial corner of

the maxilla as in typical balaenopterids. The parietal is exposed

in the intertemporal region as a subtle sheet anterior to the ante-

riormost portion of the supraoccipital. Posterior to the frontal,

it is highly concave and forms the anteromedial wall of the tem-

poral fossa. Approaching the lambdoidal suture it becomes later-

ally convex. The posteromedial wall of the temporal fossa

(which is formed by the squamosal) is concave. The posterodor-

sal border of the parietal, the anterodorsal border of the squa-

mosal, and the posterolateral edge of the supraoccipital are

interdigitated in a complex manner at the level of the lambdoi-

dal suture (Text-fig. 5) as in modern balaenopterids.

A

B

TEXT -F IG . 5 . Restoration of the vertex structure of

Archaebalaenoptera castriarquati. A, photographic plate. B, line

drawing for explanation. Scale bar represents 100 mm.

A

sq

pmx

papmx

apmx

apmx

n

n

n

n

p

p

p

soc

sop

soc

apmx

apmx

n

nip irfr

mx

nf

p

sop

sq

irfr

irfr

ip

ip

C

B

TEXT -F IG . 4 . Protrusion marking the anterior border of the

parietal in balaenopterids (black arrows). A, Balaenoptera

acutorostrata (AMNH 35680). B, Archaebalaenoptera

castriarquati, left side. C, the same, right side. Not to scale.

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1107

Interparietal. The interparietal is a short, wide bone below and

anterior to the anterior border of the supraoccipital (Text-fig. 5,

ip). It separates the supraoccipital from the interorbital region

of the frontal.

Squamosal. In dorsal view the lambdoidal crest is triangular-

shaped, displaying a posterior acute apex between the posterior

portion of the temporal crest and the lateral squamosal crest

(Text-fig. 3). Like that of Megaptera, the posterior apex of the

lambdoidal crest is located more to the posterior than that of

the living Balaenoptera, but it does not protrude as much poste-

riorly as in archaeocetes and cetotheres. The zygomatic process

of the squamosal is long and dorsoventrally deep; its anterior

apex is broken but it is reasonable to hypothesize that it articu-

lated with the postorbital process of the supraorbital process of

the frontal as in the living Balaenoptera and Megaptera, and in

other fossil taxa. The zygomatic process of the squamosal

diverges from the longitudinal axis of the skull and develops

outward as in the living Megaptera and the fossil ‘Plesiocetus’

cortesii (Cortesi 1819; van Beneden 1875; Strobel 1881; Portis

1885). The postglenoid process of the squamosal appears broken;

for this reason the glenoid cavity seems flat. However, judging

from the curvature of the glenoid cavity in lateral view, it seems

that this cavity was not highly concave as in modern rorquals

and humpbacks. The secondary squamosal fossa, the squamosal

protrusion (sensu Sanders and Barnes 2002b), and a bulging of

squamosal and parietal into the temporal fossa are not observed

in the holotype skull. The temporal fossa is not overhung by the

temporal crest developed by the dorsal borders of parietal, squa-

mosal, and supraoccipital (Text-figs 2A, 3A).

Occipital region. The supraoccipital is a complex structure

formed by a horizontal anterior portion and vertically bent ex-

occipitals. The anterior portion is approximately triangular with

lateral sides slightly converging towards the longitudinal axis of

the skull; the anterior border is narrow and has a rounded

anterior apex. The supraoccipital is anteriorly narrowed by a

marked transverse constriction; its lateral borders diverge poste-

riorly. Posterior to the transverse constriction, the lateral edges

of the supraoccipital diverge and project toward the posterior

apex of the lambdoidal crest at the posterolateral corner of the

skull. The anterior border of the supraoccipital is located more

to the anterior than the anterior apex of the zygomatic process

of the squamosal. The anteriormost portion of the supraoccipital

is horizontal and flat; a sagittal crest begins 50 mm posterior to

the apex. It is impossible to follow the route of this crest owing

to destruction of the posterior of the bone. About 160 mm pos-

terior to the apex of the anterior process of the supraoccipital,

the bone becomes almost vertical. A pair of tubercles is located

between the horizontal anterior portion and the vertical exocci-

pitals; the dorsal surface of the tubercles is rough. These tuber-

cles are observed in several Cetotherium-like cetothere taxa and

eschrichtiids (see below). Morphological information about the

foramen magnum and occipital condyles is missing from the

specimen owing to poor preservation.

Dentary. The dentaries are partially crushed under the skull. The

condyle is deformed and pushed against the posterior wall of the

temporal fossa; the coronoid process is broken and has been

pushed downward by the pressure of the supraorbital process of

the frontal. The dentary is straight with a slight outward curva-

ture; it does not display any anterior torsion. Dorsal and ventral

borders are parallel; the anterior apex of the mandible is robust

and dorsoventrally deep. The medial wall of the dentary is verti-

cal (flat) over the whole length of the ramus; the lateral wall is

slightly convex; the dorsal border of the ramus is crest-like. The

mandibular channel appears at the anterior end of the dentary

where it develops ventrally, making an anterior opening evident.

The left dentary bears five mental foramina and the right den-

tary bears ten.

Basicranium. The ventral surface of the posterior portion of the

skull is badly damaged and virtually no features can be des-

cribed. By contrast, the anterior portion of the skull is in a good

state of preservation. The dentaries are closely associated with

the lateroventral borders of the maxillae and their position pre-

vents a detailed description of the infraorbital plate of the max-

illa and the ventral surface of the supraorbital process of the

frontal. The maxillae are flat and wide; on the median line they

have a ventral keel, which is round and wide. It is not clear if

the vomer appears between the maxillae on the median line

because of erosion of the medial borders of the maxillae. The

keel is attenuated on the distal quarter of the rostrum but does

not disappear completely. The suture between maxilla and pala-

tine is not observed because of poor preservation of the speci-

men in that region. Such details as the position of the foramen

pseudovale, the organization of the pterygoids, the pterygoid fos-

sae and the posterior morphology of the palatines are not pre-

served.

Comparative analysis

Archaebalaenoptera castriarquati differs from extant bala-

enopterids in the morphology of the anterior process of

the supraoccipital, the shape of the ascending process of

the maxilla, the pattern of the articulation between max-

illa and premaxilla, the caudal placement of the posterior

apex of the lambdoidal crest, the long nasal bones, the

slightly concave glenoid fossa of the squamosal, and the

long, straight dentary. Each of these features is analysed

in some detail below.

Supraoccipital. In living members of Balaenoptera and

Megaptera (including the living Megaptera novaeangliae

and the fossil M. miocaena; Kellogg 1922), the anterior

process of the supraoccipital is wide and nearly squared

(Text-fig. 6). In Parabalaenoptera baulinensis (Zeigler

et al. 1997), the lateral edges of the supraoccipital con-

verge towards the longitudinal axis of the skull and there

is no transverse constriction of the anterior portion of

that bone. The anterior border of the supraoccipital

in P. baulinensis is squared, resembling that of living

1108 P A L A E O N T O L O G Y , V O L U M E 5 0

rorquals, but it differs from them in being consistently

narrower. In A. castriarquati the anterior portion of the

supraoccipital is transversely compressed and its anterior-

most border has convex lateral edges with a narrowly

rounded apex. In living M. novaeangliae the anterior por-

tion of the supraoccipital is rounder than in Balaenoptera,

but it is less transversely compressed than A. castriarquati.

The latter shares the transverse compression of the anter-

ior portion of the supraoccipital with some rorqual-like

mysticetes such as Cetotherium (Cetotheriophanes) capelli-

nii (Capellini 1875), ‘Plesiocetus’ cortesii (as represented

by the skeleton from Cortandone MGPT13808, Piedmont;

Portis 1885), Plesiocetus dyticus (Cabrera 1926), Idiocetus

longifrons IRSN Ct.M.718 (van Beneden 1886), Mesocetus

longirostris (van Beneden 1886, pl. 34), and Metopocetus

durinasus (Kellogg 1968a). Interestingly, Fordyce et al.

(1995, fig. 6c) published the dorsal view of what they

called the ‘Balaenoptera sp. of Bearlin (Early Pliocene,

New Zealand, Mysticeti)’, in which the anterior portion

of the supraoccipital is round and the ascending process

of the maxilla is round with an unexpanded posterior

end; in these features this skull resembles that of

A. castriarquati.

Ascending process of the maxilla. In all the living members

of Balaenoptera the ascending process of the maxilla is

posteriorly expanded and terminates abruptly near the

supraoccipital. In B. musculus and B. siberi (Pilleri 1989) it

makes contact with the anterior process of the supraoccipi-

tal. In A. castriarquati it is transversely narrow and lacks

the posterior expansion; moreover, it is divided from the

supraoccipital by the interposition of a narrow sheet of

parietal exposed on the cranial vertex and by the interpari-

etal. This species differs from Parabalaenoptera baulinensis

in that the maxilla of the latter has a very long and subtle

ascending process (comparatively longer than that of living

rorquals, humpbacks and A. castriarquati). However, the

ascending process of the maxilla of A. castriarquati is more

similar to that of living rorquals than that of humpbacks

because in Megaptera this formation is shorter, wider and

terminates anterior to the orbit; in A. castriarquati, living

rorquals, and in the fossil B. siberi and P. baulinensis the

posterior end of the ascending process terminates at the

level of the posterior half of the orbit.

Borders of the maxilla. In living rorquals and humpbacks,

the lateral and medial sides of the maxilla are straight;

only in B. musculus does the lateral border of the maxilla

display a strong outward convexity, resembling that

observed in the fossil Pelocetus calvertensis (Kellogg 1965).

Moreover, in B. musculus the medial side of the maxilla

displays a medial convexity anterior to the narial fossa

allowing for the placement of the anteriorly expanded

premaxillae. This feature is also present in several fossil

mysticetes, such as ‘Aulocetus’ sammarinensis (Capellini

1901), Cophocetus oregonensis (Kellogg 1934a), Cetothe-

rium moreni (Kellogg 1934b), Diorocetus hiatus (Kellogg

1968b) and Aglaocetus patulus (Kellogg 1968c).

Lambdoidal crest. In archaic mysticetes (sensu Geisler and

Luo 1996 and including nominal cetothere taxa) and liv-

ing neobalaenids (Beddard 1901; Baker 1985) the poster-

ior apex of the lambdoidal crest is posterior to the

occipital condyles; this arrangement is observed in basi-

losaurines, dorudontines and early diverging odontocetes

(Fordyce 1981, 2002; Dubrovo and Sanders 2000), and in

mysticetes (e.g. Kellogg 1965); it is therefore regarded as a

primitive condition. In balaenids and living balaenopte-

rids the posterior apex of the lambdoidal crest is anterior

to the occipital condyles. In the Rio Carbonari skull it is

CA

DB

TEXT -F IG . 6 . Comparison of the

supraoccipital of Archaebalaenoptera

castriarquati (A) with those of other

balaenopterid species. B, Megaptera

novaeangliae. C, Balaenoptera

acutorostrata. D, Balaenoptera physalus.

Scale bars represent 100 mm.

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1109

located more to the posterior than in living rorquals and

humpbacks; the apex is, however, anterior to the condy-

les. In Balaenoptera acutorostrata, it is located approxi-

mately at the middle of the distance between the

zygomatic process of the squamosal and the postglenoid

process; in other balaenopterids and Parabalaenoptera

baulinensis it is located slightly posteriorly; in

Archaebalaenoptera castriarquati it is located very

posteriorly.

Nasal bones. The shape of the nasal bones is one of the

most typical characteristics of A. castriarquati. The nasals

are elongated and transversely narrow; their posterior

borders are located well within the frontal approaching

the anterior process of the supraoccipital; the frontal is

interposed between their posterolateral corners. As shown

in Table 2, the longitudinal length of the nasal bones of

A. castriarquati approaches four times their combined

width. The ratio between nasal length and combined

width of this species is approximately twice that of

living rorquals; however, this value is close to that of

P. baulinensis (Zeigler et al. 1997).

Glenoid fossa of the squamosal. The glenoid fossa of the

squamosal is nearly flat in A. castriarquati while in

rorquals it is very concave and half-moon shaped. A flat

glenoid fossa is also found in several archaic mysticetes,

such as Diorocetus hiatus, Parietobalaena palmeri (Kellogg

1968c, d), and Aulocetus sammarinensis (Capellini 1901).

Dentary. A straight dentary like that of A. castriarquati is

found in several fossil mysticetes including cetotheres

(such as Mesocetus siphunculus, Diorocetus hiatus and

Parietobalaena palmeri; Kellogg 1968a–c), balaenids (e.g.

Balaenula astensis; Bisconti 2000) and rorqual-like mystic-

etes such as Cetotherium (Cetotheriophanes) capellinii

(Capellini 1875) and ‘Plesiocetus’ cortesii (van Beneden

1875). Extant rorquals and humpbacks have outward

arched dentaries.

Other comparisons. The Rio Carbonari skull also differs

from living rorquals and humpbacks in having tubercles

on the dorsal surface of the supraoccipital; in this feature

it is similar to cetotheres (such as Cetotherium rathkei,

Metopocetus durinasus and Mixocetus elysius) and the grey

whale Eschrichtius robustus in which these formations are

emphasized.

Archaebalaenoptera castriarquati shares with Megaptera

novaeangliae the outward projection of the zygomatic

process of the squamosal, which is divergent from the

longitudinal axis of the skull in dorsal view; moreover, it

shares with living rorquals and humpbacks the abruptly

depressed supraorbital process of the frontal, the presence

of a maxilla with a long and definite ascending process,

and the wide, flat supraorbital process of the frontal. It

differs from M. affinis in the morphology of the maxilla

(van Beneden 1882, pl. 42); the anterolateral border of

the maxilla of M. affinis is convex and round like that of

Balaenoptera musculus and B. siberi, whereas it is straight

in A. castriarquati. Moreover, in M. affinis the anterior-

most portion of the premaxilla is not transversely expan-

ded as in A. castriarquati.

Balaenoptera sibbaldina is represented by a newborn

skull, some periotics and tympanic bullae, and several

postcranial bones (van Beneden 1882, pls 49–51). There is

no adult skull to compare with A. castriarquati. I suggest

that it should be re-studied in order to assess its validity

as a taxon; the morphological evidence on which it is

based seems too scanty and ambiguous.

Archaebalaenoptera castriarquati differs from B. muscu-

loides in the outward curvature of the dentary; the man-

dible of B. musculoides is bowed outward (van Beneden

1882, pl. 52) while that of A. castriarquati is mainly

straight. Moreover, A. castriarquati is smaller overall than

B. musculoides. The outward curvature of the dentary is

also the principal difference between A. castriarquati and

B. borealina (van Beneden 1882, pl. 66).

Archaebalaenoptera castriarquati differs from B. rostra-

tella (van Beneden 1882, pl. 76) in several ways. The latter

has occipital condyles that are dorsoventrally shorter than

those of A. castriarquati; the dentary is bowed outward

while that of A. castriarquati is straight; the vertex struc-

ture differs from that of all of the other balaenopterids,

including A. castriarquati, in that the parietals meet along

TABLE 2 . Relationship between length and width (in mm) of

the nasals in selected balaenopterid mysticetes. #, specimen

number.

Taxon l ¼ nasal

length

w ¼ width of

both nasals

l ⁄ w Mean

Archaebalaenoptera

castriarquati*

250 70 3Æ57 3Æ57

Parabalaenoptera

baulinensis�250 64 3Æ90 3Æ90

Balaenoptera

musculus�#1: 320 #1: 200 #1: 1Æ6 1Æ36

#2: 280 #2: 250 #2: 1Æ12

Balaenoptera

physalus�#1: 250 #1: 200 #1: 1Æ25 1Æ215

#2: 130 #2: 110 #2: 1Æ18

Balaenoptera

borealis�#1: 260 #1: 130 #1: 2 1Æ75

#2: 266 #2: 152 #2: 1Æ75

#3: 165 #3: 100 #3: 1Æ65

#4: 160 #4: 100 #4 : 1Æ6Balaenoptera

acutorostrata�#1: 84 #1: 55 #1: 1Æ53 1Æ345

#2: 111 #2: 110 #2: 1Æ009

#3: 105 #3 : 70 #3: 1Æ5

*This paper.

�Zeigler et al. (1997).

�Tomilin (1967).

1110 P A L A E O N T O L O G Y , V O L U M E 5 0

the midline in front of the anterior process of the supra-

occipital forming a longitudinally evident sagittal suture.

With respect to this last point, B. rostratella resembles the

archaic cetotheres.

‘Burtinopsis’ similis differs from A. castriarquati because

it has an outward-bowed dentary. ‘Burtinopsis’ minutus is

very poorly known (van Beneden 1882, pls 97–102); it is

not possible to compare it with A. castriarquati. ‘Burtin-

opsis’ was placed in synonymy with Balaenoptera by

Demere (1986).

Balaenoptera sursiplana (as reviewed by Kellogg 1965)

is represented by few skeletal elements and cannot be

compared with A. castriarquati. Eschrichtius cephalus (Kel-

logg 1965) differs from A. castriarquati because the dorso-

ventral diameter of its dentary diminishes anteriorly

instead of being constant. Archaebalaenoptera castriarquati

differs from Balaenoptera davidsonii (Demere 1986)

because the dentary of the latter is c. 900 mm longer and

has a slighter outward curvature.

PHYLOGENETIC ANALYSIS

Material and methods

The phylogenetic relationships of A. castriarquati were

investigated through a cladistic analysis of 165 characters

scored for 35 taxa. The name, repository (only for speci-

mens I examined), age, and relevant literature for the taxa

employed in this study are given in the Appendix along

with a character list and taxon · character matrix. The

characters used are discussed in Bisconti (2003a, b, 2005);

they are derived partly from my own observations on the

specimens listed in the Appendix and partly from the lit-

erature. In particular, I prepared the character list after

having studied the evidence provided in the papers of

Miller (1923), Kellogg (1928, 1931, 1965, 1968a–c), Fraser

and Purves (1960), Barnes and McLeod (1984), McLeod

et al. (1993), Fordyce (1994), Geisler and Luo (1996,

1998), Messenger and McGuire (1998), Luo and Ginge-

rich (1999), Bisconti (2001, 2003a, b, 2005), Kimura and

Ozawa (2002), Sanders and Barnes (2002), Geisler and

Sanders (2003) and Demere et al. (2005).

The goal of the study was to understand the phylo-

genetic position of A. castriarquati with respect to the

other balaenopterid whales, and to assess the phylogenetic

relationships of Balaenopteridae and Eschrichtiidae with

respect to cetotheres, Balaenidae and Neobalaenidae. I

have not tried to resolve the phylogenetic relationships of

the cetotheres but the analysis does provide some sugges-

tions about their position among the baleen whales. The

taxonomic sample was chosen in an attempt to include

representatives of all of the major mysticete radiations.

Two of the taxa used in the phylogenetic analysis require

comment. ‘Plesiocetus’ cortesii was described by Cortesi

(1819) and subsequently by others (Cuvier 1823; van Ben-

eden 1875; Strobel 1881) up to its destruction during a

bombing raid over the Museo di Storia Naturale, Milano,

where it was stored during the Second World War; it

consisted of a nearly complete skeleton of a basal

balaenopterid. This was also used by Zeigler et al. (1997)

in an analysis of the phylogenetic relationships of

Parabalaenoptera baulinensis. Given that the specimen is

lost, the morphological assessment herein relies on a

reconstruction based on images (Bisconti, in press b).

Specimen MPST 240505 represents a Late Miocene bala-

enopterid from northern Italy that has been described

elsewhere (Bisconti 2003a).

Character states were treated as unordered and un-

weighted by PAUP 4.0b10 (Swofford 2002) under the

ACCTRAN character-state optimization. The search for

the most parsimonious cladograms was made by tree-

bisection-reconnection (TBR) with ten replicates and one

tree held at each step during stepwise addition followed

by bootstrap analysis with 1000 replicates. A randomiza-

tion test was performed by PAUP to assess the distance

of the results from 10,000 cladograms sampled equiproba-

bly from the set of all possible trees generated from the

original matrix; the test was performed by combining ten

different randomization tests each of which generated a

random distribution of 1000 cladograms sampled equi-

probably from the set of all possible trees.

The degree of agreement between the phylogenetic

results and the stratigraphic occurrence of the taxa was

evaluated by the calculus of the Stratigraphic Consis-

tency Index (SCI) developed by Huelsenbeck (1994).

This index is obtained by dividing the number of strati-

graphically consistent nodes against the total number of

nodes on the cladogram excluding the root; the total

number of nodes is calculated as the total number of

taxa minus 2 (for discussions on the SCI, see Siddall

1995; Clyde and Fisher 1997; Hitching and Benton

1997). The index ranges from 0 to 1, the latter being

the maximum agreement between phylogenetic results

and stratigraphic age of the taxa.

Results

The TBR algorithm found nine most parsimonious trees

that were 503 steps long. A strict consensus of them is

shown in Text-figure 7, and the tree statistics are presen-

ted in the corresponding caption. The randomization test

provided significant results because the mean length of

10,000 trees generated equiprobably from the matrix used

in the cladistic search was 973,887 steps with a standard

deviation of 46Æ763, which is much higher than that of

the most parsimonious trees found by TBR (503 steps).

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1111

Thus, the probability that the TBR results were due to

chance was significantly low (P < 0Æ0001).

The calculus of the SCI was negatively influenced by

the presence of two unresolved polytomies in the strict

consensus tree. These polytomies lowered to 25 from a

total of 33 the number of nodes for which it was possible

to assess the stratigraphic consistency. The SCI of the

strict consensus TBR tree of Text-figure 7 was 0Æ757. The

SCI calculated for the cladograms found by Kimura and

Ozawa (2002) ranged from 0Æ3 to 0Æ5 depending on the

number of taxa and on the balaenid species included. The

SCI calculated for the cladogram of Dooley et al. (2004)

was 0Æ562 and the SCI calculated for the morphology-

based cladogram of Demere et al. (2005, fig. 3) was 0Æ44.

In conclusion, despite the negative influence of the unre-

solved polytomies, the SCI of the most parsimonious

trees found in this study is comparatively much higher

than those of other recent studies, suggesting that the

phylogenetic results are in better agreement with the

stratigraphic occurrence of the taxa.

In the strict consensus tree, A. castriarquati occupies a

basal position in the Balaenopteridae. It is the sister spe-

cies of a clade including ‘Plesiocetus’ cortesii, Parabalae-

noptera, Balaenoptera and Megaptera. Parabalaenoptera

forms a clade together with ‘Balaenoptera’ borealina (spec-

imens assigned to this species are listed in the Appendix

and are limited to earbones), and MPST 240505. They

form the sister clade of Megaptera and Balaenoptera. The

living M. novaeangliae forms a clade together with

M. miocaena and M. hubachi. The living Balaenoptera

includes two clades, one formed by B. physalus, B. muscu-

lus and B. acutorostrata, the other including B. edeni,

B. borealis and B. omurai.

The grey whale Eschrichtius robustus and the Pliocene

‘Balaenoptera’ gastaldii are the sister taxa of the three Ceto-

therium-like mysticetes Cetotherium rathkei, Mixocetus

elysius and Metopocetus durinasus. Cetotheres from the Cal-

vert Formation, USA (Parietobalaena palmeri, Diorocetus

hiatus, Pelocetus calvertensis), and from Japan (Isanacetus

laticephalus) are located in basal positions in the lineage

leading to Balaenopteridae. This lineage also includes

‘Aulocetus’ sammarinensis from the Middle Miocene of

Italy, which is the sister species of a clade including Balae-

nopteridae, Eschrichtiidae and Cetotherium-like mysticetes.

The 50 per cent majority rule cladogram only partially

supports the above results (Text-fig. 8). In the bootstrap

tree Balaenoptera, Megaptera and Parabalaenoptera col-

lapse, forming an unresolved node; the basal position of

MCA 240536 and of ‘Plesiocetus’ cortesii is confirmed as

the sister group of ‘Aulocetus’ sammarinensis and the

clade including Eschrichtiidae, Balaenopteridae and

Cetotherium-like cetotheres. The monophyly of Balae-

nopteridae, Eschrichtiidae, Balaenoidea, Balaenomorpha,

Chaeomysticeti, Aetiocetidae and Mysticeti is supported by

the analysis. High bootstrap values support the monophyly

of Mysticeti, Chaeomysticeti, Balaenomorpha, Balaenoidea,

Aetiocetidae and Balaenopteridae. In conclusion, the over-

all pattern of mysticete phylogeny as depicted by the most

parsimonious strict consensus tree of Text-figure 7 is con-

firmed by the bootstrap analysis but more evidence needs

to be provided to support species relationships among

Balaenopteridae, Cetotherium-like mysticetes, and such

archaic taxa as Pelocetus calvertensis, Diorocetus hiatus,

Parietobalaena palmeri and Isanacetus laticephalus.

DISCUSSION

Phylogenetic remarks

The phylogenetic analysis reinforces a traditional view in

which Balaenopteridae includes three subfamily rank

groups, namely Balaenopterinae, Megapterinae and

Parabalaenopterinae. The morphological support for the

Parabalaenopterinae is weak but the monophyly of this

group represents the most parsimonious solution found.

Together with the recognition of these groups, the results

also show that A. castriarquati and ‘Plesiocetus’ cortesii are

TEXT -F IG . 7 . Phylogenetic relationships of Archaebalaenoptera

castriarquati. Strict consensus tree from nine equally

parsimonious trees. Tree statistics: tree length, 503 steps;

Consistency Index (CI), 0Æ5447; Retention Index (RI), 0Æ8115;

Homoplasy Index (HI), 0Æ4553; Rescaled CI, 0Æ4421.

1112 P A L A E O N T O L O G Y , V O L U M E 5 0

the most basal balaenopterids. These forms are from

Early–Late Pliocene deposits in northern Italy and their

primitive morphology contrasts sharply with their relat-

ively young age, suggesting that the Mediterranean Sea

played a role in preserving ancient balaenopterid diversity

when more advanced forms (Megaptera, Parabalaenop-

tera) were already living elsewhere.

At present, A. castriarquati may be considered the most

primitive balaenopterid mysticete but its position will

probably change in due course; there is a rich fossil

record of balaenopterid mysticetes around the world and

it is anticipated that new taxa will be described. One of

the most surprising results of my study is that A. castri-

arquati is more primitive than ‘Plesiocetus’ cortesii, which

has been regarded as the most primitive balaenopterid

since Zeigler et al. (1997).

It is apparent that current morphological evidence

for the phylogenetic relationships of the species belong-

ing to Balaenoptera, as reviewed by Demere et al.

(2005), is deceptive. Both the results presented herein

and those of Demere et al. (2005) are characterized by

insufficient bootstrap support values to warrant a

robust interpretation. I think that this situation is not

a result of scanty morphological analysis, rather that

the inclusion of other fossil balaenopterid taxa will

enhance our ability to resolve the phylogenetic history

of recent Balaenoptera species. Descriptions of new fos-

sil rorqual-like mysticetes are currently in progress (Bis-

conti in prep.; Bisconti and Demere in prep.), which

will serve future analyses.

Feeding adaptations

Sanderson and Wassersug (1993) reviewed knowledge of

the feeding behaviours of living mysticetes. They des-

cribed (p. 40) three feeding types and provided a list of

synonyms of the behavioural nomenclature proposed in

previous literature. The feeding types are: continuous ram

feeding (typical of balaenids), intermittent suction feeding

(supposed to be typical of eschrichtiids) and intermittent

ram feeding (typical of balaenopterids). Bisconti and

Varola (2000) used the conceptual framework of Sander-

son and Wassersug (1993) to infer the feeding behaviour

of a Late Miocene cetothere with double coronoid process

on its dentary.

Archaebalaenoptera castriarquati shows primitive charac-

ters in feeding-related structures: a squamosal with a

nearly flat glenoid fossa (Text-figs 2–4) and a straight den-

tary. These characters must have influenced the feeding

TEXT -F IG . 8 . Phylogenetic

relationships of Archaebalaenoptera

castriarquati: 50 per cent majority rule

tree obtained from the data matrix in

the Appendix. Numbers above the

branches are bootstrap support values.

Tree statistics: CI, 0Æ568; RI, 0Æ7582; HI,

0Æ5173; rescaled CI, 0Æ3659.

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1113

behaviour of this taxon. The glenoid fossa of living bala-

enopterids is strongly concave (True 1904). Among living

baleen whales, only rorquals and humpbacks possess an

elastic tissue at their cranio-mandibular joint (CMJ; see

Kimura 2002 and references therein), which is of great

importance in feeding behaviour (Pivorunas 1979). Miller

(1923) suggested that the osteological correlate of the elas-

tic tissue is represented by the strongly concave glenoid

fossa of the squamosal. Archaic mysticetes, with some

exceptions, are characterized by flat glenoid fossae, and

this suggests that they did not possess elastic tissue at the

CMJ (see Kimura 2002). This hypothesis was also suppor-

ted by Bisconti and Varola (2000) based on the reconstruc-

tion of the musculature of a dentary with bifid coronoid

process. Here it is hypothesized that A. castriarquati did

not possess the elastic tissue at its CMJ because the glenoid

fossa of its squamosal is flat.

Lambertsen et al. (1995) defined the types of motions

affecting the dentary of balaenopterids during feeding:

alpha-rotation (inward and outward motion of the den-

tary during opening and closing of the mouth), delta-

rotation (depression and elevation of the dentary) and

omega-rotation (medial and lateral rotation of the

condyle of the dentary). They suggested that the alpha-

rotation is enhanced by the outward curvature of the

dentary, i.e. that a straight dentary should alpha-rotate

less efficiently than an outward bowed dentary. It is

therefore hypothesized that the alpha-rotation of the

nearly straight dentary in A. castriarquati was less marked

than the dentaries of living rorquals and humpbacks.

In conclusion, A. castriarquati had primitive feeding-

related structures that did not enable intermittent ram

feeding in the same way as in living rorquals and hump-

backs. It is likely that it did not possess elastic tissue at

the CMJ, and that it was unable to open and close its

mouth as efficiently as living balaenopterids.

CONCLUSIONS

Archaebalaenoptera castriarquati represents a new genus

and species of Balaenopteridae. It is basal in the radiation

of this group and more primitive than ‘Plesiocetus’ cort-

esii. Its feeding-related traits prevented it from inter-

mittent ram feeding, which is typical of the living

Balaenopteridae, as efficiently as in modern rorquals and

humpbacks. It is primitive in several respects including in

the orientation of the zygomatic process of the squamo-

sal, the mainly straight dentary, long nasal and anteriorly

expanded premaxilla. Its relatively young age (Early Plio-

cene) contrasts with its primitive morphology, suggesting

that the Mediterranean played a role in preserving ancient

balaenopterid diversity at a time when more advanced

forms (Megaptera, Parabaenoptera) were already living.

Acknowledgements. I thank Carlo Francou (MGPC) who invited

me to study the mysticete fauna of Castell’Arquato and provided

logistic assistance. Giancarlo Artoni kindly helped me during my

numerous visits to MGPC. I thank Gianluca Raineri (Riserva

Naturale Geologica del Piacenziano, Castell’Arquato) very much

for providing stratigraphic data and information on the mollusc

content of the Rio Carbonari Basin; moreover, he provided very

helpful logistical assistance on a number of occasions. Walter

Landini read and commented on an early draft of the paper.

Annalisa Berta and Tom Demere provided interesting discus-

sions on the relationships of the whale described. Thanks are

also due to the referees and editors for their help. The research

was supported by the PhD funds of the Dipartimento di Scienze

della Terra, Universita di Pisa.

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APPENDIX

List of specimens employed in the cladistic analysis

Protocetus atavus: SMNS 11084 (holotype); Middle Eocene. Geor-

giacetus vogtlensis: Hulbert et al. (1996), Hulbert (1998); Middle

Eocene. Zygorhiza kochii: USNM 4748, 16638, 449538; Kellogg

(1936), Uhen (1998); Late Eocene. Chonecetus goedertorum: Bar-

nes et al. (1994); Late Oigocene. Aetiocetus polydentatus: Barnes

et al. (1994); Late Oligocene. Eomysticetus whitmorei: ChM

PV4253 (holotype), Sanders and Barnes (2002); Late Oligocene.

Caperea marginata: AMNH AMO 36692, IRSN 1536, ISAM ZM

41126, 19944, 40626, 14407; Beddard (1901), Baker (1985);

Recent. Balaena mysticetus: USNM 257513; ZML 1680, 3997,

2563, 2001, ‘Balaena japonica’ (1–2); Bisconti (2003a), Burns

et al. (1993), Reeves and Leatherwood (1985); Recent. Balaena

montalionis: MSNT MC CF 31 (holotype); Bisconti (2000,

2003a); Early Pliocene. Balaenula astensis: MSNT MC CF 35

(holotype); Bisconti (2000); Early Pliocene. Eubalaena glacialis:

AMNH 42752, 256803, 90241; MSNT 264; USNM 267612,

3339990, 23077, 301637; Bisconti (2003a), Cummings (1985),

True (1904); Recent. Eubalaena australis: ISAM ZM 2284, 40710,

48950, 13370; Cummings (1985). Pelocetus calvertensis: USNM

11976 (holotype); Kellogg (1965); Early Miocene. Isanacetus lati-

cephalus: Kimura and Ozawa (2002); Early Miocene. Parietobal-

aena palmeri: AMNH 128885; USNM 10677, 16570, 24883,

10909; Kellogg (1968d); Early Miocene. Diorocetus hiatus: USNM

16783 (holotype), 205990; Kellogg (1968c); Early Miocene. Ceto-

therium rathkei: Pilleri (1986); Middle Miocene. Mixocetus elysi-

us: Kellogg (1931); Middle Miocene. Metopocetus durinasus:

USNM 60460 (holotype); Kellogg (1968a); Middle Miocene.

Eschrichtius robustus: AMNH 181374, 34260, 1750 (‘Eschrichtius

cephalum’), A; NMB 42001; USNM 364969, 364580, 571931,

364969, 364977, 364970, 364973, 504305; ZML St20350, St13130,

630 (‘Eschrichtius gibbosus’); True (1904), Wolman (1985);

Recent. ‘Balaenoptera’ gastaldii: MGPT 13802 (holotype); Portis

(1885); Early Pliocene. ‘Aulocetus’ sammarinensis: MGB 9073

1CMC172 (1–6) (holotype); Capellini (1900), Bisconti (in press);

Middle Miocene. Archaebalaenoptera castriarquati: MCA 240536

(inventory of the Soprintendenza per i Beni Archeologici

dell’Emilia Romagna; holotype); Bisconti (2003b); Middle Plio-

cene. ‘Plesiocetus’ cortesii, the Mount Pulgnasco whale: Cortesi

(1819), Cuvier (1823), van Beneden (1875), Strobel (1881), Bis-

conti (in press b); Middle Pliocene. MPST 240505 (inventory of

the Soprintendenza per i Beni Archeologici dell’Emilia Romag-

na); Bisconti (2003b); Late Miocene. Balaenoptera borealina:

IRSN CtM775a–b, 774 (type), 777, 778; van Beneden (1882);

Early Pliocene. Parabalaenoptera baulinensis: Zeigler et al.

(1997); Late Miocene. Megaptera hubachi: Dathe (1983); Middle

Pliocene. M. miocaena: Kellogg (1922); Late Miocene. M. novae-

angliae: AMNH 24679; MSNT 263; USNM 269982, 486175 (1–

2), 13656 ⁄ 16252, 21492; ZMA 14964–14967, 14953 (1–2), 14952

(1–2); ISAM ZM 39781, 2288; Winn and Reichley (1985),

Clapham and Mead (1999); Recent. Balaenoptera acutorostrata:

AMNH 181411, 35680; IRSN 1537; MSNT 260, 261; ZMA

12873; ISAM ZM 40626, 36715, 39672; Stewart and Leatherwood

(1985), True (1904); Recent. B. physalus: AMNH 35026, 256796;

MSNT 251–253, 255, 257, 258; ZMA 14950 (1–2), 14927 (1–2),

14935 (1–2), 23353, 14947; Gambell (1985); Recent. B. musculus:

AMNH 234949, 256797, 256798; MSNT 250; ZMA 23354–23356,

14946, 14942, 14961; True (1904), Yochem and Leatherwood

(1985); Recent. B. edeni: USNM 504692, 236680 (1–3); ISAM

ZM 12962, ZM 40449; Junge (1950); Recent. B. omurai: Wada

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1117

et al. (2003); Recent. B. borealis: USNM 504698, 504699, 504701,

504244, 486174; Gambell (1985); Recent.

Character list

Character states are from personal observations and literature

listed in the phylogenetic analysis section (see ‘Material and

methods’). Some of the characters are commented on or des-

cribed in detail whenever their telegraphic description may leave

room for ambiguous interpretations.

1. Suprameatal area of petrosal: 0, low; 1, high.

2. Air sinus: 0, absent; 1, present around the tympanic bulla.

3. Ascending temporal crest: 0, absent; 1, present. The ascending

temporal crest represents the anteriormost attachment site for

the temporalis muscle and is located on the dorsal surface of

the supraorbital process of the frontal.

4. Parietal and squamosal are bulged into the temporal fossa: 0,

no; 1, yes.

5. Ascending process of maxilla: 0, absent; 1, present and nar-

row; 2, present and wide.

6. Plate-like infraorbital process of the maxilla: 0, absent; 1,

present.

7. Zygomatic process of maxilla bears a steep face that clearly

separates the rostrum from the antorbital process of the fron-

tal: 0, no; 1, yes.

8. Wide and bulbous basioccipital crest: 0, no; 1, yes.

9. Mandibular symphysis: 0, present; 1, absent (groove for men-

tal ligament present).

10. Tympanic membrane: 0, present; 1, modified into glove

finger. This is a soft-tissue character. Fraser and Purves

(1960) found that the tympanic membrane was modified

into a glove finger-like shape in all of the living mysti-

cetes they analysed.

11. Foramen ‘pseudo-ovale’: 0, absent; 1, present and perfor-

ating styliform process of squamosal.

12. Posterior process of petrosal: 0, absent; 1, present.

13. Sternum: 0, formed by manubrium and several seternebra;

1, formed by manubrium only.

14. Number of ribs attached to the sternum: 0, several pairs; 1,

one pair.

15. Teeth in the adult: 0, present; 1, absent.

16. Dental generations developed during embryology: 0, poly-

ophiodonty; 1, monophiodonty.

17. Baleen plates: 0, absent; 1, present.

18. Lateral squamosal crest: 0, absent; 1, present. The lateral

squamosal crest is an acute keel developed along the

dorsolateral border of the squamosal being continued on

the dorsal edge of the zygomatic process of the

squamosal; it is evident in many mysticetes with the

exception of Balaenopteridae in which the crest is highly

rounded.

19. Temporal crest either partially or entirely on the dorsal sur-

face of the supraorbital process of the frontal: 0, no; 1, yes.

20. Craniomandibular joint: 0, dentary and squamosal closely

articulate each other; 1, dentary and squamosal are not clo-

sely articulated. A loose articulation is observed in all

baleen-bearing mysticetes.

21. Dentary in dorsal view: 0, straight; 1, slightly bowed; 2,

strongly bowed.

22. Parietal moved onto the posterior portion of the interorbital

region of the frontal: 0, no; 1, yes. Miller (1923) and Kellogg

(1928) described the pattern of bone interdigitation

observed in the cetacean skull. In mysticetes they found that

in cetotheres and archaic forms the parietal is exposed at the

cranial vertex; in such taxa as Parietobalaena palmeri, Dio-

rocetus hiatus, Pelocetus calvertensis and Isanacetus laticepha-

lus the anterior border of the parietal is superimposed on

the interorbital region of the frontal, which therefore nar-

rows. In Balaenidae the parietal is also partially superim-

posed onto the interorbital region of the frontal (Bisconti

2002).

23. Posterior process of periotic: 0, short; 1, long to very long.

In Basilosaurinae, Odontoceti (not included in this study)

and Eomysticetidae the posterior process of the periotic is

short; the other mysticetes have long to very long posterior

processes.

24. Supraorbital process of frontal: 0, horizontal (same height as

interorbital region); 1, gently descending; 2, horizontal

(abruptly depressed from infraorbital region).

25. Median keel on palate: 0, absent; 1, present.

26. Mandibular fossa: 0, wide; 1, small.

27. Fossa for malleus on petrosal: 0, fully developed; 1, poorly

developed or absent.

28. Fusion of posterior process of petrosal and posterior process

of tympanic bulla: 0, no; 1, yes.

29. Fusion of lateral lip of tympanic bulla with anterior process

of petrosal: 0, no; 1, yes.

30. Posterior wall of tympanic bulla: 0, convex; 1, bilobated; 2,

keeled; 3, flat.

31. Dorsoventral fissure in posterior wall of tympanic bulla: 0,

present; 1, absent.

32. Coronoid process of dentary: 0, high; 1, low (at level of dor-

sal surface of condyle or lower).

33. Rostrum in lateral view: 0, mainly straight; 1, slightly arched;

2, strongly arched.

34. Parietal exposition on the dorsal wall of the skull: 0, parietal

present; 1, parietal absent (located under the supraoccipital);

2, parietal absent (divided into two halves by the interposi-

tion of the supraoccipital). The parietal is evident at the cra-

nial vertex in archaeocetes, Aetiocetidae, Eomysticetidae,

Parietobalaena palmeri, Diorocetus hiatus, Pelocetus calverten-

sis and Isanacetus laticephalus. It is superimposed by the su-

praoccipital in Balaenidae and Neobalaenidae. It is mainly

divided into two halves by the interposition of the supraoc-

cipital in Balaenopteridae, Eschrichtiidae and, possibly, in

Cetotherium-like mysticetes.

35. Axis of main squamosal development: 0, anteroposterior; 1,

dorsoventral. A dorsoventral development of the squamosal

is observed in Balaenidae and Neobalaenidae.

36. Glenoid fossa of squamosal: 0, short and concave; 1, short

and mainly flat; 2, long and strongly concave.

37. Zygomatic process of squamosal: 0, long and slender; 1,

short and stocky; 2, long and crescent-shaped.

38. Articular surface of mandibular condyle: 0, posterodorsal; 1,

dorsal; 2, posterior.

1118 P A L A E O N T O L O G Y , V O L U M E 5 0

39. Baleen length: 0, short; 1, middle-sized (eschrichtiids); 2,

very long.

40. Manus: 0, small and slender; 1, large and wide; 2, long and

narrow.

41. Dorsoventral compression of tympanic bulla: 0, absent

(ovoid bulla, high tympanic cavity); 1, present (low bulla,

low tympanic cavity).

42. Sigmoid process of tympanic bulla: 0, high; 1, very low.

43. Dorsal border of round window: 0, round; 1, straight.

44. Anterolateral corner of tympanic bulla: 0, not evident; 1,

abruptly rounded and short; 2, gently rounded and long; 3,

squared; 4, strongly rounded and long.

45. Location of pterygoid: 0, anterior; 1, close to the posterior

border of the skull.

46. Pterygoid partially covered by palatines: 0, no; 1, yes.

47. Ventral lamina of pterygoid: 0, absent; 1, present.

48. Cervical vertebrae: 0, free; 1, fused.

49. Mylohyoidal sulcus on ventromedial surface of dentary: 0,

absent; 1, present.

50. Anterior torsion in dentary: 0, absent or slight; 1, present

and strong.

51. Dorsal fin: 0, present; 1, absent.

52. Ventral throat grooves: 0, absent; 1, present.

53. Stylomastoid fossa: 0, short and shallow; 1, long and shallow

with posterior tubercle; 2, short and deep as a notch with

floor; 3, short and deep without floor but with roof; 4, long

and shallow with roof.

54. Stylomastoid fossa: 0, not prolonged on the posterior pro-

cess of petrosal; 1, prolonged.

55. Lateral protrusion of anterior process of petrosal: 0, absent;

1, long and triangular.

56. Skull length about one-third of total body length: 0, no,

skull shorter; 1, yes.

57. Skull deep: 0, no, skull slender; 1, yes.

58. Dorsolateral borders of maxilla: 0, transversely compressed;

1, wide and flat.

59. Internal opening of the facial canal small and tubular: 0, no;

1, yes.

60. Infundibulum: 0, absent; 1, complete; 2, incomplete.

61. Large foramen transversarium in axis: 0, absent, a small

foramen is present; 1, absent at all; 2, present.

62. Lateral borders of supraoccipital: 0, continuously convex; 1,

sigmoid convexity; 2, continuously concave; 3, straight.

63. Anterior tip of supraoccipital: 0, round; 1, narrow and

squared; 2, pointed; 3, narrow and round; 4, wide and

round; 5, wide and squared.

64. Postcoronoid crest and postcoronoid fossa in dentary: 0,

absent; 1, present and wide; 2, present but highly

reduced.

65. Internal opening of facial canal coalescent into internal

acoustic meatus during late ontogeny: 0, yes; 1, no.

66. Superior process of petrosal: 0, high; 1, low.

67. Base of rostrum: 0, wide (lateral process of maxilla short); 1,

narrow (lateral process long).

68. Proportions of scapula: 0, high and very short; 1, high and

short; 2, high and very long.

69. Squamosal cleft: 0, absent; 1, present.

70. Number of digits in forelimb: 0, five; 1, four.

71. Interorbital region of frontal: 0, wide; 1, narrowed antero-

posteriorly; 2, reduced to a subtle sheet posterior to the cau-

dal tip of the ascending process of the maxilla.

72. Posteromedial elements of rostrum strongly indented: 0, no;

1, yes.

73. Caudal tip of ascending process of maxilla posterior to mid-

orbit: 0, no; 1, yes.

74. Exposition of interparietal on the dorsal wall of the skull: 0,

absent; 1, small; 2, large.

75. Dorsal surface of petrosal posterior to the anterior process:

0, strongly raised; 1, not raised.

76. Position of posterolateral corner of exoccipital relative to

postglenoid process of squamosal: 0, far and medial; 1, far

and posterior; 2, close and medial.

77. Lateral and medial borders of ascending process of maxilla:

0, parallel; 1, divergent; 2, strongly divergent.

78. Anterior tip of zygomatic process of squamosal: 0, anterior

to anterior border of supraoccipital; 1, posterior.

79. Temporal crest of parietal in front of supraoccipital: 0, pre-

sent and forming a sagittal crest; 1, absent; 2, present and

forming two opposite concavities on both sides of interpari-

etal.

80. Antorbital notch on lateral process of maxilla: 0, absent; 1,

present.

81. Posterior tip of ascending process of maxilla: 0, pointed; 1,

rounded; 2, squared.

82. Temporal crest lateral to supraoccipital: 0, not covering the

lateral wall of braincase in dorsal view; 1, overhanging and

covering the lateral wall.

83. Position of posterior apex of the lambdoid crest: 0, at level

of occipital condyles; 1, posterior to the condyles; 2, anterior

to the condyles.

84. Angular process of dentary: 0, high and squared, pterygoid

groove absent; 1, low and squared, pterygoid groove absent;

2, low and round, pterygoid groove absent; 3, very low and

squared, pterygoid groove present.

85. Anterior process of petrosal: 0, absent; 1, present and round;

2, present and squared; 3, present and triangular (lateral and

medial borders converging anteriorly).

86. Rostral end of anterior process of petrosal: 0, wide (squared

or gently rounded); 1, narrow; 2, pointed.

87. Dorsomedial border of tympanic cavity: 0, sharply depressed

from posterior to anterior; 1, not depressed.

88. Lateromedial diameter of promontorium: 0, short; 1, long.

89. Groove under the internal acoustic meatus: 0, absent; 1,

present.

90. Ascending temporal crest on supraorbital process of the

frontal: 0, at the posterodorsal edge of the process; 1, at

middle of the process; 2, moved on the anterior border of

the process.

91. Anterolateral portion of zygomatic process of squamosal: 0,

parallel to long axis of the skull; 1, slightly divergent; 2,

strongly divergent.

92. Round window confluent into perilymphatic foramen: 0, no;

1, yes.

93. Anterior tip of zygomatic process of squamosal: 0, posterior

to postorbital corner of supraorbital process of frontal; 1,

very close; 2, under the postorbital corner.

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1119

94. Ventral border of dentary: 0, transversely round; 1, crest-

like.

95. Dorsal border and ventral border of dentary parallel anterior

to coronoid crest: 0, yes; 1, no (dorsal border depressed); 2,

no (dorsal border has complex profile).

96. Proportions of the forelimb: 0, humerus longer than radius

and ulna; 1, humerus slightly shorter than radius and ulna;

2, humerus much shorter than radius and ulna.

97. Coracoid process of scapula: 0, present; 1, absent.

98. Acromial process of scapula: 0, present; 1, absent.

99. Posteromedial corner of anterior process of petrosal reaches

the anteromedial corner of promontorium in dorsal view: 0,

yes; 1, no.

100. Anterior border of nasal: 0, straight; 1, notched.

101. Medial emergence of anterior process of petrosal: 0, absent;

1, present and small; 2, present and robust.

102. Lateral emergence of anterior process of petrosal: 0, absent;

1, present and small; 2, present and robust.

103. Lateral border of anterior process of petrosal: 0, straight or

slightly convex; 1, concave.

104. Perilymphatic foramen opens into a cavity: 0, cavity small;

1, cavity large.

105. Groove for facial nerve prolonged under the posterior pro-

cess: 0, no; 1, yes, it forms a deep groove under the pro-

cess; 2, yes, the route is bounded by a robust lamina; 3,

yes, the route is bounded by a subtle lamina.

106. Anterior expansion of premaxilla: 0, absent; 1, present.

107. Lateral border of maxilla anterior to lateral process (when

present): 0, straight; 1, continuously convex; 2, sharp cor-

ner evident in posterior portion of maxilla that divides the

bone into a short posterior part (straight border parallel to

long axis of the skull) and a long anterior part (straight

border sharply converging toward long axis of the skull).

108. Posterior border of supraorbital process of frontal: 0, direc-

ted transversely; 1, directed anteriorly; 2, directed posteriorly.

109. Postorbital corner of supraorbital process of frontal projec-

ted posteriorly: 0, no; 1, yes.

110. Anterior border of supraorbital process of frontal: 0, directed

transversely; 1, directed anteriorly; 2, directed posteriorly.

111. Nasofrontal suture: 0, anterior to the interorbital region of

frontal; 1, located well into the interorbital region of fron-

tal; 2, obliterating interorbital region of frontal.

112. Anterior border of nasal in dorsal view: 0, in the anterior

half of the rostrum; 1, in the posterior half of the rostrum;

2, very close to the base of rostrum; 3, located well into the

interorbital region of frontal.

113. Contacts of alisphenoid in temporal fossa: 0, alisphenoid

in between squamosal, parietal, and palatine; 1, no alisph-

enoid exposed in temporal fossa; 2, alisphenoid in

between squamosal, parietal, and pterygoid; 3, alisphenoid

in between squamosal and pterygoid; 4, alisphenoid in

between parietal and pterygoid.

114. Alisphenoid exposition in temporal fossa: 0, large; 1, small.

115. Contact of alisphenoid with squamosal: 0, large contact

(alisphenoid nearly squared); 1, very small contact (alisphe-

noid dorsoventrally compressed, pointed contact).

116. Relationships of pterygoid and squamosal: 0, pterygoid

does not appear in temporal fossa; 1, anterolateral diameter

of pterygoid not narrowed by the interposition of the falci-

form process of squamosal; 2, anterolateral diameter of

pterygoid narrowed dorsal to hamular process owing to an

anteroventral expansion of falciform process of squamosal;

3, pterygoid subdivided into two distinct halves by the

interposition of the falciform process of squamosal.

117. Position of foramen ‘pseudo-ovale’: 0, foramen within

pterygoid; 1, foramen in between squamosal and pterygoid;

2, foramen within squamosal, contact with pterygoid (when

present) by a suture.

118. Optic tube location: 0, under the supraorbital process of

frontal; 1, slightly in front of posterior border of supraor-

bital process of frontal.

119. Optic tube: 0, ventrally open; 1, ventrally closed by a lam-

ina from the anteroventral surface of the supraorbital pro-

cess of the frontal.

120. Postglenoid process of squamosal: 0, slightly lower than

ventral surface of zygomatic process of squamosal; 1, same

level as zygomatic process of squamosal; 2, markedly lower

than zygomatic process.

121. Coronoid crest: 0, long; 1, short.

122. Medial surface of superior process: 0, flat; 1, convex; 2,

concave.

123. Dorsolateral and ventromedial surfaces of anterior process

of petrosal parallel: 0, no; 1, yes.

124. Dorsolateral surface of anterior process of petrosal oblique:

0, yes; 1, no.

125. If convex, medial surface of superior process: 0, crest-like;

1, round; 2, complex.

126. Intertemporal constriction: 0, narrow and long; 1, wide

and long; 2, wide and short; 3, narrow and short.

127. Anterior process ‘blade-like’: 0, no; 1, yes.

128. Protuberance present on premaxilla at anterolateral corner

of nasal bone: 0, no; 1, yes.

129. Elongate notch present in posterior border of palatine at

posterior end of palate: 0, no; 1, yes.

130. Lateral process of maxilla and supraorbital process of fron-

tal forms a right angle in lateral view: 0, no, the lateral pro-

cess is prolonged posteriorly and the angle is obtuse; 1, yes.

131. Ascending temporal crest developed distally over the supra-

orbital process of frontal: 0, no; 1, yes.

132. Ascending temporal crest high and sharp: 0, yes; 1, no.

133. Position of glenoid fossa of the squamosal: 0, posterior to

orbit; 1, under the orbit.

134. Lateral squamosal crest projecting anteriorly: 0, no; 1, yes.

135. Roof of stylomastoid fossa: 0, absent; 1, poorly developed;

2, developed as a strong and long structure whose border

is round.

136. Floor of stylomastoid fossa: 0, absent; 1, present and flat; 2,

present and enveloping the fossa ventrally and posteriorly.

137. Round window dorsoventrally compressed: 0, no; 1, yes.

138. Position of coronal suture: 0, anterior to the anterior bor-

der of the supraoccipital; 1, posterior.

139. Curvature of premaxilla: 0, no curvature; 1, regular curva-

ture; 2, irregular curvature. In Balaenula astensis and Eubal-

aena the anterior 25 per cent of the premaxilla is directed

ventrally, interrupting the regular curvature of the rostrum

in that region

1120 P A L A E O N T O L O G Y , V O L U M E 5 0

140. Curvature of the dorsal surface of the skull: 0, skull mainly

straight; 1, regular curvature; 2, irregular curvature. A regu-

lar curvature is observed in Balaena and Balaenella. Irregu-

lar curvature is present in Eubalaena and Balaenula.

141. Distal portion of the infraorbital plate of the maxilla: 0,

present; 1, absent.

142. Orientation of the nasals and the proximal rostrum: 0,

onward; 1, upward.

143. Relief on the parietal squama: 0, absent; 1, present.

144. Spreading of the anterolateral portion of the parietal onto

the emergence of the supraorbital process of the frontal: 0,

absent; 1, present. The spreading of the parietal onto the

emergence of the supraorbital process of the frontal is

observed in Balaenula and Eubalaena among the Balaeni-

dae.

145. Dome on the supraoccipital: 0, absent; 1, present.

146. Posterior outline of the exoccipital in lateral view: 0,

squared; 1, round.

147. Height of the ventral surface of the exoccipital: 0, lower

than the orbit; 1, at the level of the orbit; 2, higher than

the orbit.

148. Groove for the tensor tympanic muscle: 0, present; 1,

absent.

149. Dorsoventral groove medial to the zygomatic process of the

squamosal: 0, absent; 1, present.

150. Hamular process of pterygoid: 0, undefined; 1, projecting

posteriorly; 2, projecting medially.

151. Development of ascending temporal crest: 0, mainly

straight; 1, distal half abruptly projecting posterolaterally.

152. Supraorbital process of frontal: 0, very short; 1, short; 2,

long.

153. Posterior side of tympanic bulla: 0, transverse crest-like

posterior edge present; 1, straight surface.

154. Tympanic cavity: 0, a single cavity; 1, cavity divided into

two halves the anterior of which is separated by the poster-

ior one through a crest-like formation.

155. Supraoccipital breadth: 0, supraoccipital strictly compressed

transversely at the level of the posterior apex of the lamb-

doidal crest (the crest projects posteriorly and medially); 1,

supraoccipital not compressed (the crest projects posterior-

ly and laterally); 2, supraoccipital compressed at the level

of the posterior apex of the lambdoidal crest (the crest pro-

jects only posteriorly).

156. Supraoccipital length in dorsal view: 0, short length com-

pared with maximum breadth; 1, supraoccipital very long

and narrow when compared with the maximum breadth

(character observed only in Eomysticetus and Cetotheriop-

sis); 2, supraoccipital long but not narrow.

157. Dorsal surface of supraoccipital: 0, strongly concave; 1, flat;

2, anteriorly convex and posteriorly concave; 3, mainly

convex.

158. Lateral squamosal crest on the zygomatic process of the

squamosal: 0, absent; 1, present.

159. Mandibular foramen: 0, wide; 1, small.

160. Mandibular foramen: 0, round; 1, triangular.

161. Position of maximum rising of the dorsal surface of the

petrosal relative to the pars cochlearis: 0, over the pars coc-

hlearis; 1, anterior to the pars cochlearis.

162. Secondary squamosal fossa: 0, absent; 1, present.

163. Anterior process of parietal squama: 0, more posterior than

posterior border of ascending process of the maxilla; 1,

more anterior.

164. Intertemporal region distinctly depressed anterior to the

anterior border of the supraoccipital: 0, yes; 1, no.

165. Lacrimal exposed dorsally: 0, no; 1, yes.

Taxon · character matrix

Numbers refer to character states described in the list above; ?,

characters impossible to score owing to their incomplete or null

preservation; –, characters absent from a taxon but present in

other taxa.

Protocetus atavus

000000000000??00000000-000000000000000-?0000000000??00-?00

0-?0000–?0?00-0-0-000-0000-000-000????-00–?-?0000-000000-000?

????0-00—0-??000–000000000-0000000???0-0?

Georgiacetus vogtlensis

0000000000000000000000-000000000000000-00000000000??00-00

00-00000–00000-0-0-000-0000-000-0000000-00–0-00000-000000-

0000????0-00—0-??000–000000000-000000000?0-00

Zygorhiza kochii

11111000000000000000000000000100000001-00000000000??00-00

00-000000-000000000001010000-00000000000-000-0-00000-0000

00-000000000-00-000-00000–010000000000100000001001

Chonecetus goedertorum

111111111?11??0?0000000200?00100000020-?0000000000??????01?

0?0200?0?000000?000 101000??0??00000000?00???0011010110000?

0020????1011-000-???00—00001000000 0?1200???0001

Aetiocetus polydentatus

111111111?11??0?0000000200?00100000020-?0000000000??????01?

0?0200?0?000000?000101000??0??00000000?00???0011010110000?-

0020????1011-000-???00–000010000000?1200???0000

Eomysticetus whitmorei

111101111?11111111110000000001000002200?0000000000??00000

100002000000?00-000-000-0001000001000000-0000000110101100

0??011-0100110?-000-02000-?00001000000011100000100?

Balaena mysticetus

1110211111111111111121111111101121111121111111111110111-

11012001-00110010-002-1-0-1222010111010110-1000011002020

210021011-00102001001012011111110012 000021022311000010

Balaena montalionis

?110?111??11??111111?1?1?????????2111?21????111?????????10?2?01??-

???0?10-0?2-1-0-12??????11?1?????1????????2?20210021001?????2?01?0

101???1?1?110012?0002??2231???0010

Eubalaena glacialis

1110211111111111111121111111101121111121111111111110111-

11012004-00110010-002-1-0-1222011111010100-10000210000002

10021011-001020011100120112200011020000210 12311000010

Balaenula astensis

111021111111111111111111111110112111112?1111111111??11?1-

1012003-00110?10-012-1-0-1222010111010100-100001100000021

0021011-0010200?11011201122000101100 0021012311000010

Caperea marginata

11102111111111111111011011111011211111211111111100010?0-

0111-003-00121110-012-1-0-112??10110010200-10000?200202022

00100001201-2000-0110111111000101 1100011022301000010

B I S C O N T I : N E W P L I O C E N E B A L A E N O P T E R I D W H A L E F R O M I T A L Y 1121

Pelocetus calvertensis

111121111?11??111111111111111010000002010004000000??200?0

1011221000210100000111000112000111010200-00000111101012

41012000100003000-110010000-000001000 0021?22010011000

Parietobalaena palmeri

111121111?11??1111112111111110100000020?0000000000??200?0-

101?1211002??100000111000110000111010???-0000011110101241

012000101003000-010010000-0000010000 021?22210001000

Isanacetus laticephalus

111121111?11??1111111111111110100000020?0000000000??200?0-

101132?000?0?100000111000112000111010???-0000011110101241

012000100003000-010010000-000000000?02 1?2201??00001

Diorocetus hiatus

111121111?11??1111111111111110100000020?0003000000??200?0-

101112?11120?100010111000113100110010?00-000001112010124

1012000111003000-000010000-000001000 0021?22210010000

Cetotherium rathkei

111111111?11??1111111111111110110201120?0003000000??????01-

?1111???1???21121120211011??00?1001?????00????11201122210120-

011????2?00-0100???00-0000010?1?011?1201???0110

Mixocetus elysius

111111111?11??11111111111111101102011?0?0003000000?????001-

?1133???1???21121120211011??00?1001?????00?????1201122210120-

011????2?00-0000???00-0000000?11011?1201???0110

‘Aulocetus’ sammarinensis

?11111011?11??11111121?110?????10002320?????000000??????01?12-

001??0?0?2111?200200011?????20?000????0?????10111122101??011?-

???3?00-1100???00-0000000?0002??220001?0000

Metopocetus durinasus

11111??1??11???11111?1????111????2011?0?000?000000????0?0?01?1-

3?10??1?211211202110113100??001????-

00000??1???12221012????11113000-???010000-

?00?00?0??????122???10110

Eschrichtius robustus

111111111?1111111111011111111011120111100002000000110?0-

001011310111?11211211002110203101110110100101000?202011-

2221012001-210-2000-110010001-00000?00121 11012211000110

Balaenoptera acutorostrata

1110111111111111101121121111121102022202000200000001300-

0010111521112112111120100212332110200212001010102002202-

2221021101111002000-100011000-000000010102 1012201000110

Balaenoptera physalus

1110111111111111101121121111121102022202000200000001410-

001011152111211211112010021233211020021200?110113002102-

2341-11101011002000-100011000-0000000101 021012201000110

Balaenoptera musculus

1111111111111111101121121111121102022202000200000001??0-

001011152?1021121111201002023321102002120001?????0111022-

341-32101011022000-100011000-0000000101021 012201000110

Balaenoptera borealis

1110111111111111101121121111121102022202000200000001300-

0010111521112112111120100212332010201212000021112002002-

2241-21101111002000-100011000-000000010102 1012201000110

Balaenoptera edeni

1110111111111111101121121111121102022202000200000001300-

0010111521112112111120100212332010200212000021112002002-

2221121101111002000-100011000-000000011102 1012201000110

Balaenoptera omurai

1110111111111111101121121111121102022202000200000001???0-

01011152??12112111?201002123?????20?21200?0?????00100222211-

211011????2000-100011000-000000010102 1012201000110

Megaptera novaeangliae

1110111111111111111121121111121102022202000200000001300-

00101113-1112112111

120100112332010220212111110001001202231–21102-10002000-

100011000-000000010102 1012201000110

Megaptera hubachi

111111111?1111111011211211?11211020222020002000000????00-

01?11151?11211211112010011233201?220212110?200??00110222?-

??1110111?0?2000-100011000-000000010102 1012201000110

Megaptera miocaena

11111111??11??111111?1121?11111102022?0?0002000000????0?01-

01115?111?1?2111120100112?320102201????00?000???1102221–?11

02?11002000-10001100?-000000010102101220??00110

‘Plesiocetus’ cortesii

111111111?1111111?11111211111111020222000002000000?????00-

1?11121??12??2111?101001113?????22?1?000?0?????01211222?????10?

1????2?00-1000???00-0000000?0?021?122010?0110

MPST 240505

111?111?1?1111111?112112111112110202220?0002000000??41000-

1011??1110????1110?0??01??331111??1?1???0?21003111??12?????????-

11102?00?-????100?0-00??0???????10??1?110????

‘Balaenoptera’ borealina

111?1???1?11??111?11111?111112110?022?0?0002000000????00010-

11??111????????0????0????31011??1??2??0?2101??????2???????????1102?-

0???????1?0??????????0????10??????0????

Parabalaenoptera baulinensis

111011111?11??111011211211?????10202220?0002000000??????01?-

11310??0?1?2111?201000123?????22?11????0?????01110222????2102-

0????2?00-1000???00-0000000?0?021?122010?0110

Archaebalaenoptera castriarquati

?11011111?11??111111011211??????02021?0?????000?00??????01?1?1-

0???1?1?2111?10010110??????22?100????0?????12111223110?101?????-

2?00-0100???00-0000000?0?01??1220???0110

‘Balaenoptera’ gastaldii

?11111?11?11??11111121?201?110110001110?00?0011000??????01?-

12230????0?2112?1002?1020?????12?100?0??0?????1?1?012???110012-

????2000-1100???00-0000010?1211??122110?0110

1122 P A L A E O N T O L O G Y , V O L U M E 5 0