T. Servais, M. Vecoli, J. Li, S.G. Molyneux, E.G. Raevskaya, and C.V. Rubinstein: The acritarch genus Veryhachium Deunff 1954 191

Palynology, 31 (2007): 191–203© 2007 by AASP Foundation ISSN 0191-6122

INTRODUCTION

Veryhachium Deunff 1954 is a well-documented andcommon acritarch. Specimens usually have polygonalvesicles with a few, simple, undivided, distally taperingand proximally open processes or spines that lie in a singleplane. Morphotypes include triangular, rectangular, or po-lygonal vesicles with three, four, or five or more processesrespectively. Acritarchs with simple morphologies are com-mon in marine sediments throughout the Phanerozoic, andwere recorded in pioneering works such as Eisenack (1938)

THE ACRITARCH GENUS VERYHACHIUM DEUNFF 1954:TAXONOMIC EVALUATION AND FIRST APPEARANCE

Abstract

Veryhachium Deunff 1954, originally described from the Ordovician of western France, is one of the most frequently recorded acritarchgenera. Over 250 species and subspecies, from the Cambrian to the Neogene, have been attributed to the genus. This genus has a simplemorphology; it displays a triangular, rectangular, or polygonal central vesicle, with a few, simple processes drawn out from the angles ofthe vesicle in a single plane, and sometimes with supplementary or auxillary processes arising from the vesicle body. Veryhachium has beenemended and revised numerous times. The number of valid species is excessive: most are probably synonyms. To facilitate effectiveclassification, only a few morphological categories should be retained. For the Lower Paleozoic, the use of two informal groups is proposed.These are the Veryhachium trispinosum group for triangular specimens, and the Veryhachium lairdii group for rectangular forms. Althoughgenerally abundant and widespread throughout the Phanerozoic, Veryhachium is of limited biostratigraphic, paleoecologic, or paleogeo-graphic value. However, its First Appearance Datum (FAD) is of great importance for Ordovician stratigraphy; the first Veryhachiummorphotypes appear in the Tremadocian Stage, making the genus an important biostratigraphic marker.

Key words: Ordovician; Tremadocian; acritarchs; organic-walled microphytoplankton; taxonomy; biostratigraphy.

and Deflandre (1946). However, it was Deunff (1954) whoerected the genus Veryhachium to include specimens withone to eight simple processes. The diagnosis of Veryhachiumby Deunff (1954) was rather broad, and overlapped withthose of other genera; this was characteristic of taxonomyat that time. This problematic diagnosis subsequently led toclassification problems that have been discussed at lengthby various authors (e.g. Turner, 1984; Sarjeant andStancliffe, 1994). Consequently Veryhachium, like otherbroadly-defined acritarch genera such as BaltisphaeridiumEisenack 1958 ex Eisenack 1959, Micrhystridium Deflandre

THOMAS SERVAIS1

MARCO VECOLILaboratoire de Paléontologie et Paléogéographie du PaléozoïqueUMR 8014 du CNRSUniversité des Sciences et Technologies de LilleBâtiment SN5 Cité ScientifiqueF-59655 Villeneuve d’AscqFrance1corresponding author, e-mail: thomas.servais@univ-lille1.fr

JUN LINanjing Institute of Geology and PalaeontologyChinese Academy of Sciences39 East Beijing Road210008 NanjingChina

STEWART G. MOLYNEUXBritish Geological SurveyKingsley Dunham CentreKeyworthNottingham NG12 5GGUnited Kingdom

ELENA G. RAEVSKAYAInstitute of Precambrian Geology and GeochronologyRussian Academy of SciencesMakarova Embankment 2Saint Petersburg 199034Russia

CLAUDIA V. RUBINSTEINCONICETUnidad de PalaeopalinologíaIANIGLA, CRICYT, C.C. 1315500 MendozaArgentina

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1937, Multiplicisphaeridium Staplin 1961, or PolygoniumVavrdová 1966, became a typical ‘waste-basket’ genus inwhich many morphotypes could easily be stored. Fensomeet al. (1990) listed over 250 species, subspecies, and vari-eties of Veryhachium. This number is excessively high, anddoes not reflect high biologic diversity or important mor-phologic disparity.

Numerous authors have discussed Veryhachium, andproposed modified classification schemes and emendeddiagnoses which are often contradictory. For exampleSarjeant and Stancliffe (1994), on the basis of a literaturereview only, restricted the genus to specimens with onlythree or four major processes. This excludes more than halfof the validly described species. It is not the intention hereto again review the classification of Veryhachium, or toprovide another emended diagnosis. Rather, the objectiveis to propose a simple classification scheme for the triangu-lar and rectangular forms of Veryhachium in the LowerPaleozoic. In addition, the oldest stratigraphic occurrencesof Veryhachium are reviewed in order to establish preciselythe First Appearance Datum (FAD) of the genus, which hasgreat biostratigraphic importance in the Early Ordovician.

TAXONOMIC CONCEPTS

Veryhachium was erected by Deunff (1954) based onspecimens from the Ordovician of Britanny, western Francewith the following generic diagnosis:

“Microorganismes planctoniques fossiles conservés àl’état de matière organique, le plus souvent de couleurjaune ou brune parfois noire. Coque à paroi lisse ougranuleuse. Forme générale dépendant du nombre deprocessus (de 1 à 8), non globuleuse, sauf lorsqu’il n’y aqu’une seule corne. Processus presque toujours pointus,généralement longs ou très longs, souvent recourbés.Diamètre du corps de la coque 10 à 40 µm, rarementinférieur ou supérieur. Envergure total pouvant atteindre100 µm et plus” (Deunff, 1954, p. 306).

This original diagnosis included specimens with vesiclewalls that are either smooth or granulate. The vesicleoutline was considered by Deunff (1954) to generallydepend on the number of processes, which was betweenone and eight. These processes (or spines, or appendices)were described as being almost always pointed. The com-plex history of Veryhachium has been reviewed by severalauthors, including Fensome et al. (1990) and Sarjeant andStancliffe (1994). Several authors have discussed the valid-ity of the genus and its type species, Veryhachium trisulcumDeunff 1951 ex Deunff 1959, in terms of botanical nomen-clature (e.g. Loeblich and Tappan, 1976; Fensome et al.,

1990). Others have questioned the validity of a taxonomicconcept that overlaps with other genera, for instance withBaltisphaeridium and Micrhystridium (e.g. Eisenack, 1959;Downie and Sarjeant, 1963). Many authors have discussedthe morphologic concept of the genus (e.g. Eisenack, 1959;Downie, 1960; Staplin, 1961; Wall and Downie, 1963), butonly a few have published emendations (Downie andSarjeant, 1963; Turner, 1984; Sarjeant and Stancliffe, 1994).Veryhachium was first emended by Downie and Sarjeant(1963, p. 92), who restricted it to polygonal or subpolygonalspecimens bearing a few, generally three to eight, hollow,pointed spines with closed tips. The major objective was todifferentiate Veryhachium from Micrhystridium, the latteralso including specimens with a polygonal body outline butwith more than eight processes.

Loeblich and Tappan (1969) did not, as indicated in therevision by Sarjeant and Stancliffe (1994), emend thegenus, but only commented that the major processes arelocated in a single plane, and that accessory processes mayappear at various positions on the vesicle. In addition,Loeblich and Tappan (1969, p. 45) proposed the termepityche (from the Greek meaning overfold or flap) for thecharacteristic opening in Veryhachium. This is consideredto be an excystment structure. The second validly pub-lished emendation was that of Turner (1984, p. 139) whoadopted the view of Loeblich and Tappan (1969), restrict-ing the genus to specimens with processes in a single plane.Subsequently, this concept has largely been accepted in theliterature. A third emendation was published by Sarjeantand Stancliffe (1994, p. 33), who presented a rather longemended diagnosis. This stated that the major processes inVeryhachium are in a single plane; this followed the recom-mendations of Loeblich and Tappan (1969) and Turner(1984). However, an important change in the taxonomicconcept of Veryhachium proposed by Sarjeant and Stancliffe(1994) was its restriction to acritarchs having triangular orquadrangular vesicles, and thus having only three or fourmajor processes. By doing this, Sarjeant and Stancliffe(1994) excluded many species from this genus. They attrib-uted these species to a number of genera, includingDorsennidium Wicander 1974, Neoveryhachium Cramer1970, and Polygonium, which were all emended by Sarjeantand Stancliffe (1994). Mullins (2001, p. 117) pointed outthat the emended diagnosis of Veryhachium by Sarjeantand Stancliffe (1994) is contradicted by their own discus-sion on the morphological features of the genus, andtherefore highly problematic.

Sarjeant and Stancliffe (1994) radically changed thetaxonomic concepts of Veryhachium and otherpolygonomorph genera. Micrhystridium was also com-pletely revised, and many related genera were emended,or reduced to the status of subgenera. The taxonomic

T. Servais, M. Vecoli, J. Li, S.G. Molyneux, E.G. Raevskaya, and C.V. Rubinstein: The acritarch genus Veryhachium Deunff 1954 193

concepts of other established acritarch genera were alsochanged. These include Comasphaeridium Staplin et al.1965, Estiastra Eisenack 1959, Filisphaeridium Staplinet al. 1965, Pulvinosphaeridium Eisenack 1954,Solisphaeridium Staplin et al. 1965, and StriatothecaBurmann 1970. These taxonomic reconsiderations com-plicate taxonomy and classification because they do notprovide generic attributions for many species that nolonger fit within a generic diagnosis. The introduction ofsubgenera by Sarjeant and Stancliffe (1994) and Stancliffeand Sarjeant 1996) is also problematic. Although acri-tarchs are sometimes classified at the subspecies andvarietas levels, the ranks between genus and species (i.e.subgenus, sectio, subsectio, series, subseries) are rarelyused. According to the International Code of BotanicalNomenclature (I.C.B.N., Article 4.2.; Greuter et al., 2000),the creation of subgenera is theoretically possible. How-ever in practice, the establishment of these additionaltaxonomic ranks is only recommended when they areuseful and helpful for classification purposes. The cre-ation of subgenera for Micrhystridium (subgeneraBrachiprojectidium, Lecithodinium, Microbaculidinium,Nannobarbophora, and Odontothrix, all erected as gen-era by Habib and Knapp, 1982) and Veryhachium (sub-genera Veryhachium (autonym) and TetraveryhachiumStancliffe & Sarjeant 1994) has not generally helped toelucidate the taxonomic relationships of these groups.The use of the subgenera proposed by Sarjeant andStancliffe (1994) has generally not been adopted by otheracritarch workers. A further fundamental problem withthe taxonomic reconsiderations of Sarjeant and Stancliffe(1994) and Stancliffe and Sarjeant (1994; 1996) is thatthey are entirely theoretical. These are based wholly onliterature studies without the benefit of observations on,or studies of, large populations that integrate morphomet-ric studies and multivariate statistical analyses. Thechanges to several original generic diagnoses by Sarjeantand Stancliffe (1994) meant that a number of speciescould no longer be included within previously definedgenera. Therefore, Sarjeant and Stancliffe (1994) wereobliged to erect new artificial genera, such as Barbestiastra,Chalaziosphaeridium, and Striatostellula.

Servais (1997), in a revision of Striatotheca, noted thatSarjeant and Stancliffe (1994) arbitrarily changed thediagnosis of this genus to include only triangular andquadrangular forms with processes arranged in a singleplane. This change was made to conform to the changesmade to the diagnosis of Veryhachium, but not by refer-ence to populations of Striatotheca. In doing this, Sarjeantand Stancliffe (1994) eliminated the widely acceptedgenus Arkonia Burmann 1970, which should have beengiven subgeneric status in order to be consistent with their

treatment of Veryhachium. Furthermore, Sarjeant andStancliffe (1994) erected the genus Striatostellula ofwhich ‘the … diagnosis is phrased to permit inclusion intothe genus of species not yet described’. The distinctionbetween Striatostellula and Striatotheca is based onwhether the processes are confined to one plane or not.Servais (1997) rejected the genus Striatostellula, andmaintained the original definitions of Arkonia andStriatotheca by Burmann (1970), keeping both taxa atgeneric level. The emended diagnosis of Veryhachium bySarjeant and Stancliffe (1994), in which Veryhachiumwas restricted to triangular and quadrangular forms withthe processes lying in one plane, has not generally beenadopted in place of the more traditional concept thatcorresponds to the emendation of Turner (1984).

Sarjeant and Stancliffe (1994), however, pointed out afundamental problem, which is that typical ‘waste-basket’genera often need taxonomic reconsideration. However, awide discussion is usually needed to build a broad taxo-nomic consensus. Before such a consensus is reached, theemendation of Sarjeant and Stancliffe (1994) is hereinrejected and the continued use of Veryhachium as in thewidely-accepted concept of Turner (1984) is advocated,based on the following emended diagnosis:

Emended diagnosis (Turner, 1984; based on commentsby Loeblich and Tappan, 1969):

Vesicle thin-walled, polygonal, with processes from theangles forming an integral part of the vesicle, majorprocesses in a single plane, commonly with accessoryprocesses at various positions on the vesicle, processesdistally closed and simple. Surface may be ornamentedwith grana or may be smooth. Excystment is by the forma-tion of an epytiche.

The correct, full taxonomic citation for the genus isVeryhachium Deunff 1954 ex Downie 1959 emend. Turner1984. The type species is Veryhachium trisulcum Deunff1951 ex Deunff 1959 (see discussion in Fensome et al.,1990, p. 526–527).

LOWER PALEOZOIC VERYHACHIUM

Veryhachium has been recorded from sediments of Or-dovician age onwards throughout the Phanerozoic. Theoldest specimens attributed to this genus are from theCambrian, but these taxa can no longer be included inVeryhachium (see below). The youngest Veryhachiumspecies are described from the Neogene (Mathur and Mathur,1980). According to the emended diagnosis of Turner(1984), the most important characteristics that distinguishVeryhachium from other genera are the simple processes in

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a single plane, and the smooth to granulate vesicle andprocess walls. Sarjeant (1967) and Loeblich and Tappan(1969) noted differences in morphology between Ordovi-cian to Devonian Veryhachium populations and those fromthe Permian to Jurassic. Most Ordovician, Silurian, andDevonian morphotypes have three to four spines, and thushave a typical triangular or rectangular central vesicle. Thethree-spined forms correspond to the type species,Veryhachium trisulcum. However specimens of Veryhachiumfrom the Permian, Triassic, and Jurassic usually have ahigher number of spines (eight and more) that are not all inthe same plane, and the vesicles are normally small (about20 µm in diameter). This makes these younger morphotypesdifficult to differentiate from Micrhystridium. Several au-thors have therefore referred to the term Micrhystridium–Veryhachium complex in the Late Paleozoic and Mesozoic(e.g. Wall and Downie, 1963).

Most Early Paleozoic Veryhachium specimens are trian-gular or rectangular in outline. Despite this simple mor-phology, they have been attributed to a number of species.These are generally distinguished by the length of theprocesses, the size of the central vesicle, and the processlength/central body ratio. Acritarch process length is ex-tremely variable (Servais, 1993; Servais et al., 2004;Stricanne et al., 2004). Given that statistical analyses ofbiometric data have not been included in the descriptions,it is probable that many of the triangular and rectangularVeryhachium species are synonyms.

Of the trispinose (three spined) veryhachid acritarchs themost cited species include, for example, Veryhachiumdowniei Stockmans & Willière 1962, Veryhachium edenenseColbath 1979, Veryhachium trispinosum (Eisenack 1938)Stockmans & Willière 1962, and Veryhachium trisulcum.‘Veryhachid acritarchs’ is an informal term used to desig-nate Veryhachium-like acritarchs. Wicander and Wood(1981) first used the term ‘complex’ when referring toVeryhachium trispinosum; in addition they provided acomplete synonymy for this species up to 1977. Among thequadrispinose veryhachids, with four spines and a rectan-gular central vesicle, five taxa have been most frequentlycited. These are Veryhachium lairdii Deflandre 1946 exLoeblich 1970, Veryhachium longispinosum Jardiné et al.1974, Veryhachium oklahomense Loeblich 1970,Veryhachium minutum Downie 1958, and Veryhachiumvaliente Cramer 1964. These selections are not comprehen-sive; only the most commonly used names are listed.

The number of processes in Veryhachium is variable,making it difficult to differentiate from Micrhystridium orPolygonium. Other variable parameters are the vesicle wallornamentation and the width of the base of the processes.The wall may be smooth, or bear small grana. Someveryhachid acritarchs, however, have more prominent or-

namentation, for example fine hair-like elements. Continu-ous morphologic variability from smooth to striated forms(e.g. Arkonia and Striatotheca), or taxa with grana or hairs(e.g. Villosacapsula Loeblich & Tappan 1976, orStellechinatum Turner 1984) occurs. This can lead totaxonomic difficulties. The end-members of these morpho-logic transitions are readily attributed to taxa; the interme-diate specimens, however, can be more difficult to classify.

Because the morphologic variability betweenVeryhachium specimens is extremely high, and because thecriteria used to differentiate species are mainly limited tothe process length and the central body diameter, it cansometimes be difficult to select an appropriate publishedtaxon name. For this reason, several workers, including thepresent authors, use an informal terminology to classifyVeryhachium. The trispinose specimens of Veryhachiumare termed Veryhachium trispinosum or the Veryhachiumtrispinosum group, and the rectangular specimens asVeryhachium lairdii or the Veryhachium lairdii group (e.g.Molyneux, 1987; Molyneux and Rushton, 1988; Servaisand Molyneux, 1997; Brocke et al., 2000; Servais andMette 2000; Vanguestaine and Servais 2002; Vecoli and LeHérissé, 2004; Achab et al., 2006; Molyneux et al., 2007).Before detailed revisions are made, and to facilitate com-munication, we advocate herein the usage of these twoinformal groups, at least for a provisional classification ofPaleozoic veryhachids. Thus the Veryhachium trispinosumgroup is proposed for triangular specimens, and theVeryhachium lairdii group for rectangular specimens. Rep-resentative specimens of both these groups are illus-trated in Plate 1.

PALEOGEOGRAPHIC ANDPALEOECOLOGIC DISTRIBUTION

Paleoecologic distribution

Veryhachium occurs widely in marine environments,however little is known about its paleoecology. Staplin(1961) recorded Veryhachium in quieter off-reef areasfrom the Devonian of Alberta. By contrast, Wall (1965)considered that Early Jurassic Veryhachium favouredopen marine environments. Jacobson (1979) erected sev-eral ‘classes’ for the paleoenvironmental interpretationsof acritarch assemblages. His ‘baltisphaerid–veryhachid–Polygonium’ class was attributed to open marine environ-ments in the Upper Ordovician. Dorning (1981) noted thatthree- and four-spined Silurian veryhachids were morecommon inshore. Furthermore, Dorning (1981) consid-ered acritarch assemblages of low to moderate abun-dance, including common Micrhystridium andVeryhachium, to be typical of nearshore environments.

T. Servais, M. Vecoli, J. Li, S.G. Molyneux, E.G. Raevskaya, and C.V. Rubinstein: The acritarch genus Veryhachium Deunff 1954 195

However, in a subsequent study, Dorning and Bell (1987)concluded that Veryhachium was present in most Silurianshallow open marine environments. Vecoli (2000) distin-guished a Veryhachium ‘class’ in his paleoenvironmentalinterpretation of the Ordovician of the North SaharaPlatform. This ‘class’ was considered to be dominant inlow-diversity assemblages, and was related to nearshore,

shallow marine environments, possibly indicative of re-stricted marine conditions. Li, Servais et al. (2004, table1) found Early–Middle Ordovician Veryhachium in near-shore to onshore marine settings of the Yangtze Platform.Li, Cao et al. (2004) noted that Permian Micrhystridium–Veryhachium-dominated assemblages indicate offshoremarine environments.

PLATE 1

Examples of typical Veryhachium morphotypes from the Upper Ordovician of North Africa. All specimens are from the Hirnantian ofborehole A1-70, Libya, North Africa (Vecoli, unpublished data). The scale bars all represent 10 µm.

1, 2 Veryhachium lairdii group. 3, 4 Veryhachium trispinosum group. Note the epityche(excystment structure) in 4.

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Paleogeographic distribution

Shortly after its first appearance during the Early Ordovi-cian, Veryhachium developed a wide paleogeographic dis-tribution, occurring on a number of paleocontinental blocksacross a range of latitudes. This is also true of Middle andLate Ordovician Veryhachium morphotypes, thereby elimi-nating them as paleobiogeographic indicators (Servais andFatka, 1997; Vecoli, 1999; Servais et al., 2003; Vecoli andLe Hérissé, 2004). Silurian and Devonian species ofVeryhachium were also cosmopolitan (Le Hérissé andGourvennec, 1995; Le Hérissé et al., 1997; Le Hérissé et al.,2000, table 1). Li, Cao et al. (2004, text-fig. 3) plotted allPermian localities with the Micrhystridium–Veryhachiumassemblages on a paleogeographic map, and demonstratedthat Veryhachium occurred across a wide range of latitudes,indicating a cosmopolitan distribution.

BIOSTRATIGRAPHY AND FIRST APPEARANCE

The species of Veryhachium described up to 1989 listedby Fensome et al. (1990, p. 510–528) indicate a Cambrianto Neogene range. Stancliffe and Sarjeant (1994, table 2)provided a global range chart of selected Veryhachiumspecies. Only Veryhachium dumontii Vanguestaine 1973 ispresent in the Cambrian, and the youngest species de-scribed is restricted to the Paleogene and Neogene. Thecatalog of Fensome et al. (1990) indicates that mostVeryhachium species were described from the Ordovician,Silurian, and Devonian, with more than 50 Ordovicianspecies erected, including the type species.

Records of Veryhachium from the Cambrian

Several species described from the Cambrian have beenattributed to Veryhachium. The best known is Veryhachiumdumontii, which is an excellent biostratigraphic marker forthe latest Cambrian. Vanguestaine (1973) describedVeryhachium dumontii from the Upper Cambrian of theStavelot Massif, Belgium, with a ‘flattened central body,triangular-shaped, with convex sides.’ As indicated byStancliffe and Sarjeant (1994), Veryhachium dumontii hasa non-equilateral vesicle. The central body has the shape ofan acute isosceles triangle. A detailed revision of this taxon,and of its sister taxon Dasydiacrodium caudatumVanguestaine 1973, indicates that both species are part ofa morphologic continuum (Raevskaya and Servais, unpub-lished data). Both taxa are typical of the latest Cambrianand clearly belong to the ‘diacrodian’ acritarchs, as does themorphologically similar genus Nellia Golub & Volkova inVolkova & Golub 1985, which was recently reviewed byStricanne et al. (2005). Veryhachium dumontii is thus a

‘diacrodian’ acritarch, with a bipolar body (one pole bear-ing a single process, the second pole bearing two pro-cesses), and not a ‘veryhachid’ acritarch. For this reason,Veryhachium dumontii should not be included within thegenus. It must be placed in a diacrodian genus. Moreover,Veryhachium dumontii was described as being coveredwith granules that are ‘connected by narrow ridges forminga network with meshes’ (Vanguestaine, 1973). Such a wallstructure has never been described for any other species ofVeryhachium.

Other Late Cambrian species have also been assigned toVeryhachium. Veryhachium mutabile Di Milia et al. 1989is almost circular in shape. It has a few spines that clearlydo not lie in a single plane, and thus does not correspondwith the concept of Veryhachium as emended by Turner1984. A possible Late Cambrian synonym of this specieswas described in open nomenclature by Martin and Dean(1981) as Veryhachium sp. A, with processes that areobviously not distributed in a single plane. Both species canpossibly be included in Dorsennidium. Other veryhachidspecies which appear in the Cambrian (Downie, 1984) areDorsennidium minutum (Downie 1958) Sarjeant &Stancliffe 1994 and Impluviculus milonii (Deunff 1968)Loeblich & Tappan 1969. Both species were first describedfrom the Lower Ordovician, but have subsequently beenfound in Cambrian sediments. Impluviculus milonii can bedistinguished from Veryhachium by its generally muchsmaller size and a circular opening in the center of thevesicle, and Dorsennidium minutum has processes that arenot located in a single plane. Several other acritarch speciesdescribed from Cambrian sediments have been assigned toVeryhachium. These include the Russian speciesVeryhachium parvum Timofeev 1959 ex Martin 1973,Veryhachium petrolitanum German in German & Timofeev1974, Veryhachium quadrangulum (Timofeev 1959)Fensome et al. 1990, Veryhachium quadricorne Timofeev1959 ex Martin 1973, and Veryhachium ramificatum Ger-man in German & Timofeev 1974, as well as the Chinesespecies Veryhachium yunnanense Tian 1983. None of thesespecies are consistent with the diagnosis of the genus asemended by Turner 1984 (see also Sarjeant and Stancliffe,1994), and need to be reassigned to other genera. In sum-mary, all species of Veryhachium reported from Cambrianstrata can be excluded from the genus as emended byTurner (1984). Typical Veryhachium morphotypes withprocesses in a single plane first appear in the LowerOrdovician.

First Appearance Datum (FAD)

Ordovician stratigraphy. The current Ordovician timescale is composed of three Global Series (Lower, Middle,

T. Servais, M. Vecoli, J. Li, S.G. Molyneux, E.G. Raevskaya, and C.V. Rubinstein: The acritarch genus Veryhachium Deunff 1954 197

and Upper Ordovician) and seven Global Stages(Tremadocian, Floian, Dapingian, Darriwilian, Sandbian,Katian, and Hirnantian) (Chen et al., 2006; unpublisheddata). In addition, Webby et al. (2004) introduced 19 time-slices that allow a precise international correlation, basedon chitinozoans, conodonts, and graptolites.

The oldest Veryhachium at high southern latitudes onthe margin of Gondwana. Li et al. (2003) summarized thedata on the FAD of selected Early and Middle Ordovicianacritarch taxa from the margin of Gondwana. RectangularVeryhachium morphotypes, within the Veryhachium lairdiigroup, first appear in the late Tremadocian Araneograptusmurrayi graptolite Biozone of the British biozonation. Thiscorresponds to time-slice 1c of Webby et al. (2004).Trispinose veryhachids (the Veryhachium trispinosumgroup) appear at a slightly higher level in the BritishAraneograptus murrayi graptolite Biozone, probably intime-slice 1d. Subsequently, Vecoli and Le Hérissé (2004,text-fig. 5) indicated a first occurrence of the Veryhachiumlairdii group in the Lagenochitina destombesi chitinozoanBiozone of early–middle Tremadoc age, and a first appear-ance of the Veryhachium trispinosum group at the base ofthe Arenig. The analyses of the FAD of Veryhachium

within the Cymatiogalea messaoudensis–Stelliferidiumtrifidum acritarch assemblage is summarized below, and inText-Figure 1. The first appearance is probably older thanpreviously suggested (e.g. Li et al., 2003).

Tunisia. The first appearance of the Veryhachium lairdiigroup is based on data from 1590 m in the Tt1 borehole,southern Tunisia (Vecoli and Le Hérissé, 2004, fig. 5.85),where the Veryhachium lairdii group occurs withAcanthodiacrodium angustum (Downie 1958) Combaz1967. The latter is a marker for the early and middleTremadocian in North Africa (Vecoli and Le Hérissé, 2004,text-fig. 5.31). Graptolites of the Rhabdinoporaflabelliformis group also occur at this level (Vecoli, unpub-lished data). However, the age of the first occurrence ofrectangular Veryhachium is not precisely known. Indirectcorrelation with the Lagenochitina destombesi chitinozoanBiozone suggests an assignment to time-slice 1b of Webbyet al. (2004), whereas the graptolites indicate an earlyTremadocian age, possibly corresponding to time-slice 1a.However the ages of the chitinozoans and graptolites, andtheir correlation to the time-slices of Webby et al. (2004),need to be better constrained. Triangular forms ofVeryhachium attributed to the Veryhachium trispinosum

Text-Figure 1. First Appearance Datum (FAD) of the Veryhachium lairdii group (rectangles) and the Veryhachium trispinosumgroup (triangles). The time-slices, global stages, and biozones are taken from Webby et al. (2004).

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group have not been recorded from the Tremadocian ofNorth Africa. Their first appearance is considered to be inthe lowermost Arenig (Vecoli and Le Hérissé, 2004, text-fig. 5.104), corresponding to the Conochitina symmetricachitinozoan Biozone.

United Kingdom and Ireland. Molyneux et al. (2007)reviewed acritarch assemblages at the Tremadocian–Floianboundary, and provided data on first occurrences that allowcorrelation of the boundary. In the boundary interval at theGondwanan margin, acritarch biostratigraphy provides evenmore precise dating than that of the graptolites, with fivesub-assemblages of the characteristic Cymatiogaleamessaoudensis–Stelliferidium trifidum acritarch Biozone.This acritarch Biozone spans the late TremadocianAraneograptus murrayi and Hunnegraptus copiosus grap-tolite biozones, and the early Floian (early Arenig)Tetragraptus phyllograptoides graptolite Biozone(Molyneux et al., 2007). In the English Lake District, theVeryhachium lairdii group first appeared in the Bitter BeckFormation, within sub-assemblage 1 of the Cymatiogaleamessaoudensis–Stelliferidium trifidum acritarch assem-blage. The Veryhachium trispinosum group first appears inthe overlying Watch Hill Formation, in sub-assemblage 2of the Cymatiogalea messaoudensis–Stelliferidiumtrifidum acritarch assemblage. Both groups thus appear inthe late Tremadocian, within the Araneograptus murrayigraptolite Biozone. This implies that, in the English LakeDistrict, the Veryhachium lairdii group probably appearsin time-slice 1c of Webby et al. (2004), or possibly in thelower part of time-slice 1d. Furthermore, the Veryhachiumtrispinosum group appears at a higher level, probably intime-slice 1d. The Cymatiogalea messaoudensis–Stelliferidium trifidum acritarch assemblage has also beenrecorded from other localities in the United Kingdom andIreland, and includes the Veryhachium lairdii group insouth Wales (Molyneux and Dorning, 1989) and Ireland(Connery and Higgs, 1999; Todd et al., 2000). Independentage control on these deposits is usually lacking (Molyneuxet al., 2007).

Spain. Another section with graptolite biostratigraphiccontrol is in the western Sierra Morena, southwest Spain(Servais and Mette, 2000). The Veryhachium lairdii groupappears in the Araneograptus murrayi and/or theHunnegraptus copiosus graptolite biozones in the BarrigaShale Formation which is tentatively correlated with sub-assemblage 3 to 4 of the English Lake District on the basisof acritarch assemblages (Molyneux et al., 2007, text-fig.4). Although of late Tremadocian age, the precise age is notknown. The acritarch-bearing horizons may range intotime-slice 1c of Webby et al. (2004) or earlier.

Germany. Servais and Molyneux (1997) recorded rect-angular Veryhachium in the Cymatiogalea messaoudensis–

Stelliferidium trifidum acritarch assemblage from Rügen,northeast Germany. In comparison with the English LakeDistrict, these horizons probably correspond to sub-assem-blage 1 (to 2) of the Cymatiogalea messaoudensis–Stelliferidium trifidum acritarch assemblage, which isequivalent to the Araneograptus murrayi graptolite Bio-zone and probably to time-slice 1c (Molyneux et al., 2007,text-fig. 4). The acritarch-bearing levels at Rügen areindependently dated by chitinozoans (the Lagenochitinadestombesi chitinozoan Biozone) that suggest a middleTremadocian age (Samuelsson et al., 2000; Servais et al.,2001), possibly corresponding to time-slice 1b of Webby etal. (2004).

Bohemia. A single sample (KL-7) from the lower KlabavaFormation of the Prague Basin, Czech Republic, containedspecimens from both the Veryhachium lairdii andVeryhachium trispinosum groups (Fatka, 1993). It alsocontains the chitinozoan Amphorachitina conifundusPoumot 1968, suggesting a latest Tremadocian age(Araneograptus murrayi or Hunnegraptus copiosus grap-tolite biozones).

Belgium. The Cymatiogalea messaoudensis–Stelliferidium trifidum acritarch assemblage from theLierneux Member of the Stavelot Inlier, eastern Belgium,investigated by Vanguestaine and Servais (2002) and Breuerand Vanguestaine (2004), has been correlated with thelatest Tremadocian sub-assemblage 4 of the English LakeDistrict (Molyneux et al., 2007, text-fig. 4). This assem-blage contains both the Veryhachium lairdii andVeryhachium trispinosum groups.

Turkey and Argentina. Similar assemblages attributedto the peri-Gondwanan acritarch province have been re-corded along the Gondwanan margin throughout the Lowerand Middle Ordovician (Servais et al., 2003). Assemblagesfrom southeast Europe, the Middle East, and Argentina aresimilar to those from European localities attributed to theGondwanan border. The Cymatiogalea messaoudensis–Stelliferidium trifidum acritarch assemblage of western andsouthern Europe has also been recorded from Turkey(Martin, 1996) and Argentina (Rubinstein and Toro, 1999;2001; Rubinstein et al., 1999). However, none of theseassemblages included Veryhachium. The first occurrencesof Veryhachium in Argentina are in the lower and middleArenig (Floian), with the Veryhachium lairdii group firstappearing in the South American Didymograptus deflexusgraptolite Biozone. The Veryhachium trispinosum groupfirst appears in the South American Didymograptus bifidusgraptolite Biozone (Rubinstein et al., 1999). Both of thesegraptolite biozones can be approximately correlated withthe upper Floian (lower to middle Arenig), correspondingto time-slices 2b and 2c. It is possible that Veryhachium ispresent earlier in Argentina.

T. Servais, M. Vecoli, J. Li, S.G. Molyneux, E.G. Raevskaya, and C.V. Rubinstein: The acritarch genus Veryhachium Deunff 1954 199

China. The South Chinese Yangtze Platform was alsoclose to the Gondwanan margin during the Ordovician, andthe Early and Middle Ordovician acritarch assemblagesbelong to the peri-Gondwanan acritarch province (Servaiset al., 2003). The FADs of both the Veryhachium lairdii andVeryhachium trispinosum groups in South China are in theTetragraptus approximatus graptolite Biozone at the baseof the Floian (earliest Arenig). This is based on occurrencesin the Tonggao Formation at the Xiayangao section, SanduCounty, southern Guizhou, China (Xu, 2001). Veryhachiumhas not been recorded from Chinese Tremadocian strata.

Baltica. Veryhachium has not been recorded from theTremadocian of Baltica. Uutela and Tynni (1991) first re-corded Veryhachium lairdii in the Baltoscandian KundaStage, of Darriwilian age. The oldest rectangular Veryhachiumfrom Baltica was recorded from the lower part of the LeetseFormation in the Lava River section, which is within theTetragraptus phyllograptoides graptolite Biozone of earlyFloian age (Molyneux et al., 2007, text-fig. 5).

Possible paleogeographic radiation

This review indicates that the Veryhachium lairdii groupprobably appeared in the middle Tremadocian, at horizonscorrelated with the Lagenochitina destombesi chitinozoanBiozone, corresponding to time-slice 1b of Webby et al.(2004), and possibly earlier, at levels where graptolites ofthe Rhabdinopora flabelliformis group occur. TheVeryhachium lairdii group is present in the Araneograptusmurrayi graptolite Biozone, possibly corresponding totime-slice 1c of Webby et al. (2004), or at least early intime-slice 1d. The Veryhachium trispinosum group firstoccurred slightly later in the Araneograptus murrayi and/or Hunnegraptus copiosus graptolite biozones, and there-fore probably in time-slice 1d (Text-Figure 1). The firstoccurrences are from localities at the Gondwanan margin inNorth Africa and from Avalonia (i.e. the English LakeDistrict and Rügen Island, Germany), which are consideredto be from high latitudes (> 60°) in the Southern Hemi-sphere (Servais et al., 2003). Veryhachium has not beenrecorded earlier than the earliest Floian (earliest Arenig) inChina, which was located at intermediate latitudes (be-tween 30° and 60° S), and in Argentina, located at similarlatitudes as China, Veryhachium has not been recordedlater than the middle Floian (early–middle Arenig). Thefirst occurrence of Veryhachium in Baltica is also in theearly Floian, but it did not become common until theDarriwilian. This suggests that Veryhachium first appearedin the Tremadocian at high latitudes before it radiated to thelower latitudes of the Gondwanan margin (China andArgentina) and Baltica during the Floian, to become cos-mopolitan by the Middle Ordovician.

CONCLUSIONS

Veryhachium is one of the most frequently recordedacritarch genera and has been revised and emended nu-merous times. The number of described species is clearlyexcessive and many names are probably synonyms. Fol-lowing previous studies, and in order to facilitate classi-fication, the use of two informal groups is proposed formorphotypes with simple morphologies. These are theVeryhachium trispinosum group for triangular specimens,and the Veryhachium lairdii group for rectangular speci-mens. However, these two groups (or complexes) shouldonly be used as utilitarian categories until detailed taxo-nomic revisions are complete. Such revisions will clarifythe precise status of all species of Veryhachium, and makeclear what species names are junior synonyms.

Veryhachium is of limited biostratigraphic, paleogeo-graphic, or paleoecologic value, because it has wide strati-graphic, biogeographic and ecologic distributions. How-ever, the FAD is of great importance for Ordovician stratig-raphy. The Veryhachium lairdii group probably first appearsin the middle Tremadocian (time-slice 1b of Webby et al.,2004). It is unequivocally present in the Araneograptusmurrayi graptolite Biozone in the late Tremadocian (time-slice 1c of Webby et al., 2004). The Veryhachium trispinosumgroup appears slightly later, in the Araneograptus murrayiand/or Hunnegraptus copiosus graptolite biozones in the lateTremadocian (time-slice 1d of Webby et al., 2004). Thismeans that both these easily identifiable morphotypes areimportant biostratigraphic markers for the Early Ordovician.The detailed revision of the first occurrences of the genusindicate that Veryhachium appeared at high latitudes duringthe earliest Ordovician, before it radiated to lower latitudesand became cosmopolitan by the Middle Ordovician.

ACKNOWLEDGMENTS

We acknowledge the careful reviews of Gary L. Mullins(Leicester, United Kingdom), Paul K. Strother (Boston,Massachusetts, U.S.A.), and Reed Wicander (Mount Pleas-ant, Michigan, U.S.A.), and the editorial work of James B.Riding (Nottingham, United Kingdom). This paper is aresult of a French–Argentinian ECOS-Sud collaborationprogramme (no. A05U01), a French–Chinese collabora-tion (CNRS–CAS), and a NSFC Grant (no. 40670214). Itis a contribution to the International GeoscienceProgramme IGCP 503 ‘Ordovician Palaeogeography andPalaeoclimate.’ Stewart G. Molyneux publishes with theapproval of the Executive Director, British GeologicalSurvey (NERC). Li Jun and Elena G. Raevskaya ac-knowledge the Université des Sciences et Technologiesde Lille, France, for the position of visiting professor.

200 PALYNOLOGY, VOLUME 31 — 2007

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