A New Gobiosuchid Crocodyliform Taxon from the Cretaceous ...

Copyright q American Museum of Natural History 2004 ISSN 0003-0082

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Number 3458, 31 pp., 11 figures October 28, 2004

A New Gobiosuchid Crocodyliform Taxon fromthe Cretaceous of Mongolia

DIEGO POL1 AND MARK A. NORELL2

ABSTRACT

We describe a new fossil crocodyliform, Zaraasuchus shepardi, found in the CretaceousRed Beds of Zos Canyon (Gobi Desert, Mongolia). Z. shepardi shares numerous derivedcharacters with Gobiosuchus kielanae, also known from the Late Cretaceous of Mongolia(Bayn Dzak locality). However, it is distinguished from the latter by the presence of a mod-erately large infratemporal fenestra, anterior margin of infratemporal fenestra almost com-pletely formed by the postorbital, retroarticular process with a well-developed ornamentedposterolateral pointed process, and extremely well-developed keels on dorsal and lateral cer-vical osteoderms (the heights of which are approximately as long as the lateromedial extensionof the dorsal osteoderms).

A phylogenetic analysis indicated that these two taxa form a monophyletic group locatedbasally among crocodyliforms. This clade is diagnosed by 14 synapomorphies (e.g., anteriorand posterior palpebrals sutured to each other and to the frontal, excluding it from the orbitalmargin, external surface of ascending process of jugal exposed posterolaterally, dorsal surfaceof posterolateral process of squamosal ornamented with three longitudinal ridges, dorsal sur-face of osteoderms ornamented with anterolaterally and anteromedially directed ridges, cer-vical region surrounded by lateral and ventral osteoderms sutured to the dorsal elements, andclosed supratemporal fenestra).

INTRODUCTION

Numerous fossil vertebrates were foundduring the last decade by joint expeditions ofthe Mongolian Academy of Sciences and the

1 Division of Paleontology, American Museum of Natural History ([email protected]).2 Division of Paleontology, American Museum of Natural History ([email protected]).

American Museum of Natural History toCretaceous beds of the Gobi Desert (Dash-zeveg et al., 1995; Novacek, 1996, 2002).Fossil crocodyliforms from these beds arenot abundant, although several taxa have

2 NO. 3458AMERICAN MUSEUM NOVITATES

been described (see Storrs and Efimov, 2000;Pol and Norell, 2004).

Here we report a new form from Zos Can-yon, a poorly known locality, yet one that isrich in crocodyliforms. Recently we de-scribed another taxon, Zosuchus davidsoni,from the same beds (Pol and Norell, 2004).The phylogenetic relationships of these taxaare analyzed through a parsimony analysis inthe context of Crocodyliformes. The newtaxon, Zaraasuchus shepardi, shares severalderived characters with Gobiosuchus kielan-ae, forming with the latter a basal crocody-liform clade. This is in accordance with theprevious hypotheses of the relationships ofGobiosuchus kielanae (Clark, 1986; Ortegaet al., 2000; but see Wu et al., 1997).

The following acronyms are used through-out this work:

AMNH American Museum of Natural Histo-ry, New York

BSP Bayerische Staatssammlung fur Pa-laontologie und Geologie, Munich,Germany

CNM Chongqing Natural Museum, Sich-uan, People’s Republic of China

DGM Departamento de Producao Mineral,Rio de Janeiro, Brazil

GPIT Institut und Museum fur Geologieund Palaontologie, Universitat Tu-bingen, Tubingen, Germany

IGM Mongolian Institute of Geology,Ulaan Bataar, Mongolia

IVPP Institute of Vertebrate Paleontologyand Paleoanthropology, Beijing, Peo-ple’s Republic of China

LACM Los Angeles County Museum, LosAngeles, CA

MAL Malawi Department of Antiquities,Malawi

MACN Museo Argentino de Ciencias Natur-ales, Buenos Aires, Argentina

MAL Malawi Department of Antiquities,Malawi

MB Institut fur Palaontologie, Museumfur Naturkunde, Humbolt-Universitat,Berlin, Germany

MCZ Museum of Comparative Zoology,Harvard University, Cambridge, MA

MLP Museo de La Plata, La Plata, Argen-tina

MOZ Museo Profesor J. Olsacher, Zapala,Argentina

MUC-PV Museo de Geologıa y Paleontologıa,Universidad Nacional del Comahue,Neuquen, Argentina

PVL Instituto Miguel Lillo, Tucuman, Ar-gentina

RCL Museo de Ciencias Naturales, Ponti-ficia Universidade Catolica de MinasGerais, Brazil

SAM-K South African Museum, Cape Town,South Africa

SMNS Staatliches Museum fur NaturkundeStuttgart, Stuttgart, Germany

UA University of Antananarivo, Mada-gascar

UCMP Museum of Paleontology, Universityof California, Berkeley, CA

ZPAL Instytut Paleobiologii PAN, Warsza-wa, Poland

SYSTEMATIC PALEONTOLOGY

CROCODYLOMORPHA WALKER, 1970

CROCODYLIFORMES HAY, 1930(SENSU CLARK, 1986)

GOBIOSUCHIDAE OSMOLSKA, 1972

Zaraasuchus shepardi, new genus,new species

HOLOTYPE: IGM 100/1321, posterior re-gion of the skull and lower jaws preservedin articulation with cervical vertebrae, osteo-derms, and forelimb elements.

ETYMOLOGY: Zaraa, Mongolian for hedge-hog in reference to the spiny character of theskull and osteoderms, and shepardi, in ref-erence to Dr. Richard Shepard, a friend ofthe expedition for many years.

DIAGNOSIS: Small crocodyliform diag-nosed by the following combination of char-acters: sculptured skull bones that are orna-mented with thin and continuous ridges; an-terior margin of infratemporal fenestra al-most completely formed by the postorbital;retroarticular process with a pointed, well-developed posterolateral process, the surfaceof which is ornamented; extremely well-de-veloped keels on dorsal and lateral cervicalosteoderms, the heights of which are approx-imately equal in length to the lateromedialextension of the dorsal osteoderms.

DESCRIPTION

SKULL

The skull of IGM 100/1321 has most ofits dorsal and lateral postorbital elements inarticulation with the posterior region of thelower jaws (figs. 1, 3). Zaraasuchus shepardi

2004 3POL AND NORELL: NEW GOBIOSUCHID CROCODYLIFORM

Fig. 1. Holotype of Zaraasuchus shepardi IGM 100/1321 in dorsal view.


Fig. 2. Right supratemporal region of Zaraasuchus shepardi IGM 100/1321 in dorsal view.

has large, laterally facing orbits. The supra-temporal fenestrae are almost completelyobliterated by a lateral expansion of the pa-rietals and frontals and by a medial expan-sion of the squamosals. These expansions aredepressed in respect to the rest of the skullroof, although this could be a preservationalartifact. A narrow oblique slit between thesquamosal, parietal, and frontal is the onlyremnant of the supratemporal opening (figs.1, 2). This differs from the derived conditionseen in Gobiosuchus kielanae, where the su-pratemporal fenestra is completely closedand the squamosal and parietals are suturedalong their entire length (ZPAL MgR-II/68and 69). This character, however, is probablysubject to ontogenetic change. In some livingcrocodylians (Osteolaemus tetraspis and Pa-leosuchus trigonatus) the supratemporal fe-nestrae may close during ontogeny. The in-fratemporal fenestra is reduced due to thewide ascending process of the quadratojugal(fig. 3). This fenestra, however, is not as re-duced as in Gobiosuchus kielanae (ZPALMgR-II/67), since the postorbital process and

the infratemporal bar of the jugal are not aswide in Zaraasuchus shepardi as in Gobio-suchus kielanae. The skull table is verybroad, being as wide as the infratemporal re-gion, as in Gobiosuchus kielanae (Osmolskaet al., 1997; ZPAL MgR-II/67, 68, and 69)and Sichuanosuchus shuhanensis (Wu et al.,1997; IVPP V 10594). The external surfaceof the skull is ornamentated with a uniquepattern of extremely thin ridges and grooves.These thin ridges are more marked and con-tinuous in comparison with the slightlymarked ornamentation preserved in some ofthe specimens of Gobiosuchus kielanae(ZPAL MgR-II/67 and 69), although this dif-ference could relate to preservational or on-togenetic causes. However the more markedsculpture of the cranium in Zaraasuchus she-pardi suggests a more advanced ontogeneticstage than that of specimens of Gobiosuchuskielanae, while the previous character of anopen supratemporal fenestra suggests a youn-ger comparable stage.

A large anterior palpebral forms most ofthe dorsal margin of the orbit of Zaraasuchus


Fig. 3. Skull of the holotype of Zaraasuchus shepardi IGM 100/1321 in (A) left lateral view; (B)right lateral view.

shepardi. The palpebral is tabular rather thantriangular as in all crocodyliforms. Its ante-rior contact with the prefrontal is not pre-served in IGM 100/1321. The dorsal surfaceof this element is heavily sculptured withthin ridges and is sutured to the frontal alongits medial margin (fig. 1) excluding the fron-tals from the orbital margin. Its posteriormargin is sutured to the the posterior palpe-

bral (fig. 1), extensively overlapping the de-pressed articular facet of this element (figs.2, 3). A similar morphology is present in Go-biosuchus kielanae (Osmolska et al., 1997;ZPAL MgR-II/68), although in this form thetwo palpebrals are completely fused andmore tigthly sutured to the frontal.

The posterior palpebral is much shorterthan the anterior element (fig. 1). This pal-


pebral dorsally covers the posterior part ofthe orbit and is firmly sutured to the post-orbital and the frontal. The large anterior pal-pebral overlaps a depressed facet of the pos-terior palpebral. Its medial edge contacts thefrontal along a straight and posterolaterallydirected suture. The posterior edge of thispalpebral overlaps the postorbital and pro-jects a pointed posterolateral process alongthe lateral edge of the postorbital (figs. 1, 3).On its ventral surface, the posterior palpebralhas a short descending process that anteriorlycovers the dorsal end of the descending post-orbital bar (figs. 3, 6).

The frontals are not completely fused asin some specimens of Gobiosuchus kielanae(ZPAL MgR-II/67 and 68) and other basalcrocodyliforms (e.g., Protosuchus AMNH3024; Orthosuchus SAM-K 409). The ante-rior half of the suture between the frontals isstraight, while the posterior third of this su-ture is interdigitated (fig. 1). Between thesetwo regions, the suture is not visible and thefrontals seem to be fused, at least superfi-cially. The interfrontal suture extends alonga slightly elevated ridge, similar to that pre-sent in one of the specimens of Gobiosuchuskielanae that has fused frontals (ZPAL MgR-II/69) and several other basal mesoeucrocod-ylians. The dorsal surface of these elementsis ornamented with thin ridges which radiatefrom the interfrontal suture. The frontals areposteriorly broad at their contact with the pa-rietal and postorbital and they narrow ante-riorly markedly, with their straight lateraledges forming an acute angle (fig. 1), resem-bling the condition of Gobiosuchus kielanae(ZPAL MgR-II/68).

The posterior contact with the parietal istransverse on the medial elevated region ofthe skull roof. It projects slightly anteriorlyalong the medial margin of the supratempor-al depression and then is directed laterally,entering into the supratemporal depressionwhere it continues to the slitlike supratem-poral opening (fig. 2). The frontal forms theanterolateral margin of the supratemporal slitand meets the postorbital at the anteriormosttip of this opening. Anterior to this point, thefrontal narrows, laterally contacting the pal-pebrals through a robust suture excluding thefrontal from the orbital margin (fig. 1). Theanterior tip of the frontal and its contact with

the prefrontal and nasals are not preserved inIGM 100/1321.

The ventral surface of the frontal has anextremely well-developed crista cranii (fig.4). The space between them, which enclosedthe olfactory tract of the forebrain, is verynarrow, and it was probably closed ventrallyby a ventromedial extension of the cristaecranii or an ossification fused to them (fig.4). This peculiar condition is also found inGobiosuchus kielanae (ZPAL MgR-II/68).

The parietals are fused into a single ele-ment as in all crocodyliforms (fig. 1). Theirdorsal surface is ornamented like the rest ofthe skull roof and bears a slight longitudinalridge, which is also found in Gobiosuchuskielanae and several other basal crocodyli-forms. The medial region of its dorsal sur-face is flat, resembling the condition of mostcrocodyliforms. This area is bordered by twolaterally concave ridges which demarcate theflat dorsal surface of the skull table from thesupratemporal depressions (figs. 1, 2).

The parietal is broad at its anterior edgeand continuously narrows toward the occip-ital margin of the skull, as in Gobiosuchuskielanae (Osmolska et al., 1997; ZPALMgR-II/68). The anterolateral edge of the pa-rietal forms the posterormedial margin of thesupratemporal slit opening and contacts thesquamosal at the posteriormost tip of this ap-erture (fig. 2). Posteriorly, the squamosal-pa-rietal suture is straight and extends postero-medially along the supratemporal depression.This suture continues in the same directionposterior to the supratemporal depressionreaching the posterior edge of the skull roof(fig. 1). Only the right side of the posteriormargin of the parietal is preserved in IGM100/1321. In this region, the parietal has aposterolaterally directed crest running fromthe medial ridge to the squamosal-parietalsuture, close to its posterior end (fig. 1). Un-fortunately, in this specimen, it cannot be de-termined if the parietal extended onto the oc-cipital region of the skull.

The dorsal surface of the squamosal isvery long and roughly triangular, with itsapex directed anteriorly. Its dorsal surfacehas the same ornamentation pattern as therest of the skull roof (fig. 1). Anteriorly itforms the lateral part of the supratemporaldepression and laterally it overhangs the otic


Fig. 4. Ventral surface of frontals of Zaraasuchus shepardi IGM 100/1321.

recess as in most crocodyliforms. As de-scribed previously, the squamosal contactsthe parietal along an anterolaterally directedsuture, entering the supratemporal depressionnear the posterior end of the supratemporalslit. Anterior to this point, the squamosalforms the lateral margin of the reduced su-pratemporal opening (fig. 2). The squamosalcontacts the postorbital at the anterior apexof the supratemporal opening, where thisbone overlaps the squamosal. The squamosalfacet receiving the postorbital extends ventralto it, reaching the base of the descending pro-cess of the postorbital (fig. 3). On the dorsalsurface of the skull, the postorbital-squamo-sal contact is directed posterolaterally withinthe supratemporal depression toward the lat-eral edge of the skull roof (fig. 2). This is incontrast to the laterally directed suture of Go-biosuchus kielanae (ZPAL MgR-II/69).

The skull roof is separated from the lateraledge of the squamosal by a well-developedlongitudinal ridge that runs along most of the

length of the squamosal (figs. 1, 3). Lateralto this ridge, the lateral edge of the squa-mosal has a wide, concave surface exposedlaterodorsally (fig. 3A). This longitudinalridge and the wide concave surface ventralto it closely follows the morphology pre-served in one of the specimens of Gobiosu-chus kielanae (ZPAL MgR-II/69) and resem-bles the groove for the attachment of themovable dorsal earflap on the squamosal ofextant crocodylians. In Zaraasuchus shepar-di, this concave surface is smooth, except forthe presence of several slightly markedgrooves. The ventral margin of the lateralsurface of the squamosal bears a narrow anddeep groove near its ventral margin which ispreserved only on the right side of IGM 100/1321 (fig. 3B). Posterior to the supratemporaldepression, the concave lateral surface of thesquamosal opens onto the dorsal surface ofthe skull due to a medial deflection of thelongitudinal ridge that forms its dorsal mar-gin (figs. 1, 3A).


Fig. 5. Right posterolateral process of the squamosal of Zaraasuchus shepardi IGM 100/1321 indorsal view.

The dorsal surface of the squamosal pos-terior to the supratemporal depression is bor-dered anteriorly by a transversal groove. Thisis not present in any of the Gobiosuchus kie-lanae specimens, yet it might be accentuatedby preservation, although it is present onboth squamosals in a symmetrical way (fig.1). Posterior to this transverse groove, thesquamosal bears a long posterolateral processthat, as in Gobiosuchus kielanae (Osmolskaet al., 1997; ZPAL MgR-II/68), extends to

reach the level of the posterior end of themandibular ramus. The dorsal surface of thislong process is ornamented and bears threewell-developed and sinuous crests orientedlongitudinally near its base (fig. 5). This re-gion is poorly preserved in all the specimensof Gobiosuchus kielanae; however, the spec-imen ZPAL MgR-II/68 preserves the internalmold of the posterolateral processes of thesquamosals showing similar, yet not identi-cal, ridges on its dorsal surface. The distal


Fig. 6. Ventral surface of the postorbital ofZaraasuchus shepardi IGM 100/1321.

end of the posterolateral process of the squa-mosal is distinctly outurned, as in the typespecimen of Gobiosuchus kielanae (ZPALMgR-II/67). Despite these similarities, in Za-raasuchus shepardi the posterolateral pro-cess of the squamosal is directed horizontal-ly, approximately at the same level as theskull roof, while in Gobiosuchus kielanae(ZPAL MgR-II/68) and more derived cro-codyliforms it is ventrally deflected.

Unfortunately, the occipital flange of thesquamosal and its descending process havenot been preserved in IGM 100/1321.

The dorsal surface of the postorbital is anarrow and curved bar which forms the an-terolateral margin of the skull roof (fig. 1).Posteriorly the postorbital overlaps a de-pressed articular surface of the squamosal.here the dorsal surface of the postorbital issmooth and slightly concave, continuouswith the dorsolateral concave surface of thesquamosal. Medial to this surface the post-orbital surface is ornamented and borders thesquamosal near the supratemporal slit open-ing, of which it forms the anterior apex (fig.2). In Gobiosuchus kielanae (ZPAL MgR-II/68) the postorbital contacts the parietal at itsposteromedial corner, while in Zaraasuchusshepardi this contact is not present, probablydue to the presence of the vestigial supratem-poral opening. Anterior to the supratemporalslit margin, the medial area of the postorbitaldorsal surface contacts the frontal overlap-ping this element (figs. 1, 2). The anterolat-eral margin of the dorsal surface of the post-orbital is convex and contacts the posterorpalpebral along most of its anterior margin.

The descending process of the postorbitalis covered anteriorly by the descending pro-cess of the posterior palpebral (fig. 6). Ven-trally, the descending process of the postor-bital is a flat and smooth lamina of bone thatextends medially to the ascending process ofthe jugal, reaching almost to the base of thepostorbital bar. This thin and laminar post-orbital bar is not exposed laterally as in mostbasal crocodyliforms, but projects posteriorly(thus facing posterolaterally). A similar con-dition is also present in Gobiosuchus kielan-ae (Osmolska et al., 1997; ZPAL MgR-II/67). The postorbital forms most of the ante-rior margin of the infratemporal fenestra, acondition that differs from the interpretation

of Osmolska et al. (1997) concerning thecondition in Gobiosuchus kielanae (althoughthis region is poorly preserved in all theZPAL specimens of this taxon). The poste-rior edge of the descending process of thepostorbital extensively contacts the quadra-tojugal, reaching the posterodorsal margin ofthe infratemporal opening. The broad partic-ipation of the postorbital in the posterodorsalmargin of the infratemporal fenestra in Za-raasuchus shepardi is very different from thecondition in Gobiosuchus kielanae (Osmol-ska et al., 1997).

The jugal is preserved anterior to the post-orbital bar and closely resembles the mor-phology of Gobiosuchus kielanae. The lat-eral surface of this region is exposed later-oventrally, resembling Gobiosuchus kielanae(Osmolska et al., 1997; ZPAL MgR-II/67).This surface is distinctly ornamented withslightly marked, thin grooves, except for itsventral margin, which is smooth (fig. 3A, B).

The ascending process of the jugal is, likethe descending process of the postorbital, aflat lamina facing posterolaterally. Its antero-lateral edge is sharp and superficial, while itsposterior edge is inset medially from the lat-eral ridge of the jugal (fig. 3). This laminarprocess is compressed anteromedial–postero-laterally, but is wide along its posteromedial–anterolateral axis. This peculiar morphology


is identical to that of Gobiosuchus kielanae(Osmolska et al., 1997; ZPAL MgR-II/67,69). The base of the postorbital process ofthe jugal is ornamented along its anterolat-eral edge, as in basal crocodyliforms, but itis distinctly smooth on its posteromedial re-gion (fig. 3). The ornamentation of this re-gion cannot be determined in any specimenof Gobiosuchus kielanae due to poor pres-ervation.

Below the postorbital ascending process,the external surface of the jugal bears a well-defined longitudinal ridge that divides the ju-gal into a dorsal surface facing dorsomedi-ally and a ventral surface facing ventrolat-erally (fig. 3). The latter is continuous withthe external surface of the suborbital processof the jugal and bears the same ornamentedpattern bordered ventrally by a smooth mar-gin. The dorsal surface is less ornamented,although there are some slightly markedridges and grooves on its anterior end. Thedorsal edge of this region of the jugal formsthe entire ventral margin of the infratemporalfenestra and contacts the quadratojugal at theposterior corner of this opening (fig. 3). Pos-terior to the infratemporal fenestra, the ex-tensive jugal-quadratojugal projects poster-oventrally, probably approaching the quad-rate condyles (not preserved in IGM 100/1321).

This region of the jugal is also identical tothat of Gobiosuchus kielanae (Osmolska etal., 1997; ZPAL MgR-II/68 and 69), exceptfor the ornamentation pattern that is barelypresent in this taxon (possibly due to pres-ervational causes). A similar longitudinalridge on the infratemporal region of the jugalis also present in Sichuanosuchus shuhanen-sis (IVPP V 10594), but this taxon lacks theother similarities of the jugals of Zaraasu-chus shepardi and Gobiosuchus kielanae.

The quadratojugal is preserved on theright side of IGM 100/1321. The quadrato-jugal’s posteroventral region is thickened andsculpted at its contact with the jugal (fig.5B). The ascending process is broad and di-rected anterodorsally as in basal crocodyli-forms. This region forms most of the poste-rior edge of the infratemporal fenestra andits surface is smooth. It contacts the postor-bital extensively dorsally to the infratemporalfenestra (fig. 5B). Unfortunately, its posterior

contact with the quadrate has not been pre-served.

MANDIBLE

Only the posterior regions of the mandib-ular rami of Zaraasuchus shepardi are pre-served in IGM 100/1321. Most of the lateraland ventral surfaces are ornamented with asimilar pattern to the skull bones (fig. 3). Themandibular ramus is dorsoventrally high andthe external mandibular fenestra is complete-ly closed, a condition only present in Go-biosuchus kielanae (Osmolska et al., 1997;ZPAL MgR-II/69) among basal crocodyli-forms, but also present in some derived me-soeucrocodylians (e.g., atoposaurids, somegoniopholids, Bernissartia).

Only the posterior end of the right den-tary is preserved in IGM 100/1321. Its lat-eral surface is smooth and bears a single,small neurovascular foramen. The dorsal re-gion of the lateral surface of the dentary be-low the orbits is projected medially, beingexposed laterodorsally rather than laterally(figs. 3, 4). This would produce an insetmandibular toothrow, similar to the conditionof most non-neosuchian crocodyliforms.Posteriorly, the dentaries contact the suran-gular to the level of the postorbital bar andthey seem to extensively overlap the angular,although this contact is not well preserved.

The angular is heavily ornamented andforms most of the ventral half of the lateralsurface of the mandibular ramus (fig. 3).Dorsally, the angular is bordered by the sur-angular, and the suture between them extendsposteriorly and is deflected slightly ventrallynear the posterior end of the mandibular ra-mus (fig. 3). The ventral edge of the angularbears a sharp and well-defined longitudinalridge dividing the lateral surface from a ven-tromedially facing surface of the angular (fig.7B). This morphology is not known in othercrocodyliforms except for Gobiosuchus kie-lanae (ZPAL MgR-II/68), although Shantun-gosuchus hangjinensis seems to have a sim-ilar, but less developed condition (Wu et al.,1994a). This ridge is directed posteriorlyalong a horizontal plane (fig. 3), in contrastto the condition in derived crocodyliformswhere the angular is deflected dorsally. The


Fig. 7. Posterior region of the mandibular ra-mus of Zaraasuchus shepardi IGM 100/1321 in(A) posterolateral view; (B) ventral view.

posterior end of the angular reaches the levelof the quadrate-mandibular articulation.

The surangular anteriorly contacts theposterodorsal region of the dentary near thedorsal margin of the lower jaw at the levelof the postorbital bar. Posterior to this pointthe surangular bows slightly to form the dor-sal margin of the mandible. The lateral sur-face of the surangular is heavily ornamentedand has a sharp, prominent ridge that extendsposteroventrally from its dorsal margin (atthe level of the posterior edge of the infra-temporal fenestra) up to the level of the cran-io-mandibular articulation (figs. 3, 7A). Pos-terior to this point, the ridge ventrally de-flects abruptly, forming the lateral border ofthe reduced retroarticular process (figs. 3,7A). A similar feature is also present in Go-biosuchus kielanae (Osmolska et al., 1997;ZPAL MgR-II/68) and Sichuanosuchus shu-anensis (IVPP V 10594). Medial to thisridge, the surangular is exposed laterodorsal-ly and is slightly ornamented (fig. 7A). Itsdorsomedial edge is smooth and forms thelateral wall of the articular surface for thequadrate condyles. Posterior to this point,this smooth surface of the surangular deflectsventrally, contacting the retroarticular pro-cess medially and the surangular ridge lat-erally (fig. 7A).

The dorsal surface of the articular is ex-posed posteriorly to the articular facets forthe quadrate. The lateromedial extension ofthe articular surface is reduced although itsmedial extent is poorly preserved. Posteri-orly, a reduced, flat, and triangular-shaped re-troarticular process extends ventrally, resem-bling the condition seen in most basal cro-codyliforms. The distal (posteroventral) endof the retroarticular process of Zaraasuchusshepardi, however, is uniquely autapomorph-ic in that it has a laterally curved conicalprocess ornamented with slight ridges andgrooves and four well-developed apicallyconverging ridges. This condition is absentin Gobiosuchus kielanae (fig. 7).

The ventral surface of the articular has adorsomedially directed shelf forming thesupport for the articular facet with the quad-rate. This shelf is subtriangular and is slight-ly concave on its ventral surface. A similarprocess is present in Gobiosuchus kielanae(medial process of Osmolska et al., 1997);


however, it cannot be determined if the dor-somedial tip of this process contacted the ba-sisphenoid in Zaraasuchus shepardi. Unlikein Gobiosuchus kielanae, the entire retroar-ticular region of the lower jaw of Zaraasu-chus shepardi projects medially and is not‘‘squared-off’’ (fig. 7B).

POSTCRANIUM

Several postcranial elements were found inassociation with the skull of IGM 100/1321.Some fragmentary cervical vertebral ele-ments were crushed underneath the posteriorend of the skull roof, including partially pre-served neural arches and cervical ribs. A se-ries of cervical osteoderms and a posteriorcervical were found in articulation with theskull. Posterior to these elements, the left hu-merus and ulna were also preserved in as-sociation with appendicular osteoderms.

The best preserved postcranial elementsare eight transverse rows of cervical osteo-derms found in life articulation with theskull of IGM 100/1321. The first two rowsof osteoderms seem to be composed exclu-sively of two dorsal osteoderms as in mostbasal crocodyliforms. These are heavily su-tured to each other and have rounded lateraland anterior edges (fig. 8A). The dorsal sur-face of these osteoderms is ornamented withshallow and sinous grooves and have, neartheir posterior edge, a well-developed medialkeel (fig. 8A, B). Five ridges radiate fromthis keel (two laterally, one anterolaterally,one medially, and one anteromedially). Theposterior edge of the osteoderms imbricateswith a thin smooth area of the posterior os-teoderms.

Posterior to this first pair of osteoderms,six transverse rows are composed of two dor-sal and two lateral osteoderms that arestrongly sutured to each other. The dorsalpair of osteoderms has the same ornamenta-tion pattern as the anterior ones, although themedial keel is much more developed and isdirected dorsolaterally (fig. 8A, B). Addition-ally, an accessory ridge is present on the pos-terior surface of the medial keel (fig. 8A).The lateral osteoderms also have a well-de-veloped lateral keel. This keel, however, islocated extremely close to the sutures withthe dorsal osteoderms, and the radiating ridg-

es are not as developed and seem to be ab-sent in some of the lateral osteoderms (fig.8B).

Several ventral osteoderms are preservedin the cervical region, although slightly dis-articulated. The ventral osteoderms are no-tably different from the dorsal elements. Theventral surface lacks well-developed keelsand is ornamented with slightly markedgrooves, except for the anteriormost regionwhich is smooth and imbricates with the pre-ceding element. A slight ridge is present onits ventral surface extending obliquely to thelongitudinal axis of the osteoderm, whichprojects anterolaterally. These osteodermswere probably contacted to a correspondingpair along their medial margins, as in Go-biosuchus kielanae (ZPAL MgR-II/71).

The cervical dermal armor of Zaraasuchusshepardi is unique among crocodyliforms;however, it shares with Gobiosuchus kielan-ae several derived characters (fig. 8). First,the derived presence of lateral cervical os-teoderms that are strongly sutured to a pairof dorsal osteoderms, and the presence offive radiating ridges on the dorsal surface ofthe osteoderms (fig. 8). The three anteriorridges were described as displaying a ‘‘fleurde lys’’ pattern by Osmolska et al. (1997).Other crocodyliforms have multiple ridgeson their osteoderm dorsal surface (e.g., Pris-tichampsus), but their similarities with theosteoderms of Zaraasuchus shepardi andGobiosuchus kielanae are only superficial.

Despite these similarities, the cervical der-mal armor of Zaraasuchus shepardi is distin-guished from that of Gobiosuchus kielanaeby the presence of extremely elevated keelson the posterior edge of each osteoderm rath-er than a low ridge (ZPAL MgR-II/68, 71),the presence of a thin ridge directed parasa-gittally on the posterior surface of the osteo-derm, and the ornamentation pattern of thedorsal surface of osteoderms composed byshallow grooves rather than by discrete pits(ZPAL MgR-II/71). Additionally, the firstpair of osteoderms preserved in Zaraasuchusshepardi differs in being notably narrowerand in lacking a lateral spur, although thispair of osteoderms might not be actually thefirst pair of Zaraasuchus shepardi (i.e., the‘‘nuchal’’ osteoderms sensu Osmolska et al.,1997).


Fig. 8. Cervical osteoderms of Zaraasuchus shepardi IGM 100/1321 in (A) dorsal view; (B) lateralview

In Gobiosuchus kielanae, four smoothventral osteoderms close the cervical regionventrally (Osmolska et al., 1997; ZPALMgR-II/68), while in Zaraasuchus shepardithese elements are ornamented. This differ-ence, however, is subject to ontogenetic var-

iation and it is not possible to determine howmany ventral osteoderms composed eachtransverse row in Zaraasuchus shepardi dueto its poor preservation. It is important tonote, however, that some features of Gobios-uchus kielanae are ontogenetically more ad-


Fig. 9. Appendicular osteoderms of Zaraasu-chus shepardi IGM 100/1321.

vanced (e.g., complete closure of the supra-temporal fenestrae), than in Zaraasuchusshepardi.

In addition to the dorsal osteoderms, sev-eral small and subrectangular osteodermswere found on the dorsal surface of the hu-meral and ulnar shafts (fig. 9). The preservedhumeral osteoderms are located near the prox-imal end of the humeral shaft. These areslightly ornamented with shallow grooves anda slightly marked ridge. The proximal osteo-derm overlaps the element distal to it, al-though this might not be its natural position(fig. 9). Two osteoderms were preserved onthe distal section of the ulnar shaft. These el-ements are less ornamented and more elon-gate than the humeral osteoderms (fig. 9). Go-biosuchus kielanae has appendicular osteo-derms along the hindlimbs (ZPAL MgR-II/67and 68); however, as noted by Osmolska et

al. (1997), both limbs were probably coveredby osteoderms, as suggested by the postitionof similar disarticulated appendicular ele-ments. The distribution of appendicular osteo-derms among crocodyliforms has not been ex-tensively studied, although it has been report-ed in some taxa, ranging from basal forms(CUP 2083; Wu, personal comun.) to gonio-pholids (Sunosuchus; Wu et al., 1996) and al-ligatorids (Cong et al., 1998).

The posterior cervical vertebra was foundunderneath the posteriormost preserved cer-vical osteoderms and was removed duringpreparation (fig. 10). The neural spine is dor-soventrally short and located posteriorly onthe neural arch, although the anterior edge ispoorly preserved (fig. 10A). The prezyga-pophyses are not preserved. The postzyga-pophyses are robust, short, and barely curvedlaterally (fig. 10A). Their articular facets areelevated and facing lateroventrally. A well-developed ridge extends anteriorly from thepostzygapophyseal articular facets on thedorsal region of the lateral surface of theneural arch (fig. 10B). The neural canal islarge in comparison with most crocodyli-forms. The neurocentral suture is visible onthe lateral surfaces of this cervical vertebra.Diapophyses are not well preserved, but along ridge extends posteriorly from them,ventrally on the lateral surface of the neuralarch (fig. 10C). Ventral to the diapophysealridges, a narrow concavity extends anteriorlyon the lateral surface of the centrum betweenthem and the parapophyses. The parapophys-es are extremely well developed and pro-jected laterovetrally (fig. 10B, D). A longridge extends posteriorly to these, reachingthe anteroposterior midpoint of the lateralsurface of the centrum. The centrum of thisvertebra is unusually long for a crocodyli-form, being approximately three times longerthan high. Its anterior end is notably moreexpanded than its posteiror end, mainly dueto the well-developed parapophyses (fig.10D). Its ventral surface is constricted at itsmidpoint and bears a small keel anteriorly,between the parapophyses (fig. 10D). Noneof the specimens of Gobiosuchus kielanaehas well-exposed cervical vertebrae; how-ever, as noted by Osmolska et al. (1997), thelength of the neck in specimen ZPAL MgR-II/68 is remarkalbly long and composed by


Fig. 10. Posterior cervical vertebra of Zaraasuchus shepardi IGM 100/1321 in (A) ventral view;(B) right lateral view; (C) left lateral view; (D) dorsal view.

seven postaxial vertebrae. This suggests thatat least some of the cervical vertebrae of Go-biosuchus kielanae must be unusually long,as in Zaraasuchus shepardi.

Unfortunately, only the shafts of the hu-merus and the ulna are preserved in IGM100/1321. As in Gobiosuchus kielanae, theseforelimb elements are extremely long andslender (fig. 1), even longer than the elongateforelimbs of most basal crocodyliforms.

PHYLOGENETIC ANALYSIS

The phylogenetic relationships of Zaraa-suchus shepardi were analyzed using a mod-ification of a recently published dataset (Poland Norell, 2004), which was based on theaddition of several new characters to previ-ously published matrices (Clark, 1994; Wuand Sues, 1996; Gomani, 1997; Wu et al.,

1997; Buckley et al., 2000; Ortega et al.,2000). Twelve new characters were added tothis dataset, resulting in a matrix of 192 char-acters scored across 45 taxa. As in our pre-vious study, the taxon-sampling regime is fo-cused on non-neosuchian crocodyliforms. Inour analysis characters had equal weights us-ing Nona (Goloboff, 1993). A heuristic treesearch was performed consisting of 1000replicates of RAS 1 TBR with a final roundof TBR (mult*1000; max*;), holding 20trees per replication (hold/20;). Zero-lengthbranches were collapsed using the strictestcriterion (i.e., when any possible states areshared between the ancestor and descendantnode; amb-).

Two most parsimonious trees of 633 steps(CI 5 0.37, CIinf 5 0.36, RI 5 0.67) werefound in 797 of 1000 replications. Further


Fig. 11. Strict consensus of the two most parsimonious hypotheses obtained with Nona.

searches employing 10,000 iterations of theParsimony Ratchet (Nixon, 1999) imple-mented in Nona resulted in the same set oftopologies (hitting the best length 6190times).

In all most parsimonious hypotheses, Za-raasuchus shepardi is depicted as the sistertaxon of Gobiosuchus kielanae. Both ofthese gracile armored corcodyliforms arefrom the Late Cretaceous of Mongolia (fig.11). This is a basal clade within Crocodyli-formes and is diagnosed by 14 unambiguous

synapomorphies (parietal without broad oc-cipital portion [character 32]; absence of ex-ternal mandibular fenestra [character 75];more than two parallel rows of dorsal osteo-derms [character 97]; cranial table as wide asventral portion of skull [character 174; par-alleled in Sichuanosuchus]; palpebrals su-tured to each other and the frontal, excludingit from the orbital margin [character 181];external surface of ascending process of ju-gal exposed posterolaterally [character 182];longitudinal ridge on lateral surface of jugal


below infratemporal fenestra [character 183;paralleled in Sichuanosuchus]; dorsal surfaceof posterolateral process of squamosal orna-mented with three longitudinal ridges [char-acter 184]; presence of a sharp ridge alongventral surface of angular [character 186;paralleled in Shantungosuchus]; surangularwith a longitudinal ridge on its dorsolateralsurface [character 187; paralleled in Sichu-anosuchus]; dorsal surface of osteoderms or-namented with anterolaterally and antero-medially directed ridges [character 188]; cer-vical region surrounded by lateral and ventralosteoderms sutured to the dorsal elements[character 189]; presence of appendicular os-teoderms [character 190; also present in oth-er crocodyliforms, see above]; closed, or in-cipiently close, supratemporal fenestra [char-acter 191]). Despite the large number of syn-apomorphies, support for this clade is low(Bremer support 5 2). Most other nodes ofthese hypotheses also have minimal Bremersupport values.

The phylogeny indicates that this clade ismore closely related to mesoeucrocodyliansthan to Protosuchus and its allies (Proto-suchidae sensu Clark, 1986) due to the pres-ence of five synapomorphic characters (pos-terolateral process of squamosal elongated,posterolaterally directed, and ventrally de-flected [character 36]; squamosal contactsquadrate and otoccipital lateral to crani-oquadrate passage [character 49]; maxillaand premaxilla with ventral region facing lat-erally and dorsal region facing dorsolaterally[character 139]; quadratojugal ornamented atits base [character 145]; thick, pneumaticpterygoid flanges [character 166]).

Our results conflict with those of Wu et al.(1997), where Gobiosuchus was the sistertaxon of two taxa from the Early Cretaceousof China (i.e., Sichuanosuchus and Shantun-gosuchus). Here, the clade composed by Zo-suchus, Sichuanosuchus, and Shantungosu-chus is depicted as more closely related toderived mesoeucrocodylians than to Gobios-uchus kielanae and protosuchids. This posi-tion is supported by six synapormorphies(fused frontals [character 20]; palatineshelves that extend below narial passage[character 37]; choana opens posteriorly intoa midline depression (choanal groove) [char-acter 39]; fusion of pterygoids posterior to

choana [character 41]; presence of one en-larged maxillary tooth [character 79]; pres-ence of a well-developed posterodorsal pro-cess of the premaxilla [character 125]). Inour dataset, forcing a monophyletic groupcomposed by this clade, Gobiosuchus kielan-ae, and Zaraasuchus shepardi requires fiveextra steps. Despite these signs of support forthe derived position of this clade, there are aconsiderable number of shared derived sim-ilarities between Gobiosuchus, Zaraasuchusshepardi, and these taxa. In particular, Sichu-anosuchus shares 3 of the 14 synapomor-phies of the Gobiosuchus kielanae 1 Zaraa-suchus shepardi clade (interpreted here asconvergences, see above).

The monophyly of the clade traditionallyreferred as Protosuchia (i.e., including pro-tosuchids, gobiosuchids, and the Shantun-gosuchus clade) is rejected in this analysis,although this clade is present in trees onlytwo steps longer than the most parsimonioustrees.

DISCUSSION

The presence of Zaraasuchus shepardi inCretaceous beds of Mongolia provides fur-ther insight into the diversity achieved bybasal crocodyliforms during the Cretaceous.This record, together with previously knowntaxa such as Gobiosuchus kielanae (from theBayn Dzak locality), Zosuchus davidsoni(also from the Zos Canyon beds), and prob-ably the very poorly known Artzosuchus bra-chycephalus (Efimov, 1983), represents a di-verse assemblage of basal forms recorded ex-clusively in the Late Cretaceous of Mongo-lia. Gobiosuchus parvus (Efimov, 1983)would also form part of this list, althoughthere are serious doubts on the validity ofthis species as noted by previous authors(Osmolska et al., 1997; Storrs and Efimov,2000).

ACKNOWLEDGMENTS

We thank Amy Davidson for the carefuland detailed preparation of the specimen de-scribed here (IGM 100/1321). We are alsoindebted to Mick Ellison for his marvelousphotographic artwork. Our thanks are exten-sive to H. Osmolska for her hospitality andfor allowing D.P. to study the ZPAL speci-


mens of Gobiosuchus kielanae. X.-C. Wuand Chris Brochu provided useful commentsthat markedly improved the quality of thismanuscript. We also thank the MongolianAcademy of Sciences–American Museum ofNatural History field crew that collected thespecimen reported here. Financial support toD.P. was provided by the Department ofEarth and Environmental Sciences of Colum-bia University and the American Museum ofNatural History. Accession to collectionspecimens was possible thanks to: J. Maisey(AMNH), M. Moser (BSP), M. Maisch(GPIT), X. Xing (IVPP), J.M. Clark, J.F.Bonaparte (MACN), E. Gomani (MAL), D.Unwin (MB), L.E. Ruigomez and R. Cuneo(MEF), Z.B. Gasparini and M. Reguero(MLP), F.L. de Broin (MNHN), A. Kellner(MNUFRJ), S. Cocca (MOZ), J.O. Calvo andL. Salgado (MUC-PV), J. Powell (PVL), C.Cartelle (RCL), A. Chinsamy (SAM), R.Wild (SMNS), D. Krause and G. Buckley(UA), A. Buscalioni and F. Ortega (UAM),and I.S. Carvalho (UFRJ).

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Wu, X.-C., and H.-D. Sues. 1996. Anatomy andphylogenetic relationships of Chimaeresuchusparadoxus, an unusual crocodyliform reptilefrom the Lower Cretaceous of Hubei, China.Journal of Vertebrate Paleontology 16: 688–702.

Wu, X.-C., H.-D. Sues, and Z.-M. Dong. 1997.Sichuanosuchus shuhanensis: a new? EarlyCretaceous protosuchian (Archosauria: Crocod-yliformes) from Sichuan (China), and themonophyly of Protosuchia. Journal of Verte-brate Paleontology 17: 89–103.

Young, C.C., and M.C. Chow. 1953. New fossilreptiles from Szechuan China. Acta Paleonto-logica Sinica 1: 1–87.


APPENDIX 1

CHARACTER LIST CORRESPONDING TO DATA

MATRIX USED IN PHYLOGENETIC ANALYSIS

Character definitions 1–101 are from Clark(1994) and have the same numeration as in theoriginal publication. Character 5 was excludedfrom the analysis (due to dependence on the mod-ified definition of character 6); however, its exclu-sion does not affect the outcome of the analysis(except for the tree length). The additional char-acters are also listed here and their respectivesources are cited along with the character numberof the original publication. Characters 1, 3, 6, 23,37, 45, 49, 65, 67, 69, 73, 77, 79, 83, 90, 91, 96,97, 103, 104, 105, 107, 126, 143, 149, and 165were set as ordered characters (also marked witha ‘‘1’’ in this list).

Character 1 (modified from Clark, 1994: char.1): 1 External surface of dorsal cranial bones:smooth (0), slightly grooved (1) and heavily or-namented with deep pits and grooves (2).

Character 2 (modified from Clark, 1994: char.2): Skull expansion at orbits: gradual (0), orabrupt (1).

Character 3 (modified from Clark, 1994: char.3): 1 Rostrum proportions: narrow oreinirostral(0), broad oreinirostral (1), nearly tubular (2), orplatyrostral (3).

Character 4 (Clark, 1994: char. 4): Premaxillaparticipation in internarial bar: forming at least theventral half (0), or with little participation (1).

Character 5 (Clark, 1994: char. 5): Premaxillaanterior to nares: narrow (0), or broad (1).

Character 6 (modified from Clark, 1994: char.6): 1 External nares facing anterolaterally or an-teriorly (0), dorsally not separated by premaxil-lary bar from anterior edge of rostrum (1), or dor-sally separated by premaxillary bar (2).

Character 7 (Clark, 1994: char. 7): Palatal partsof premaxillae: do not meet posterior to incisiveforamen (0), or meet posteriorly along contactwith maxillae (1).

Character 8 (Clark, 1994: char. 8): Premaxilla-maxilla contact: premaxilla loosely overlies max-illa (0), or sutured together along a butt joint (1).

Character 9 (modified from Clark, 1994: char.9): Ventrally opened notch on ventral edge of ros-trum at premaxilla-maxilla contact: absent (0),present as a notch (1), or present as a large fe-nestra (2).

Character 10 (Clark, 1994: char. 10): Posteriorends of palatal branches of maxillae anterior topalatines: do not meet (0), or meet (1).

Character 11 (Clark, 1994: char. 11): Nasalcontacts lacrimal (0), or does not contact (1).

Character 12 (Clark, 1994: char. 12): Lacrimal

contacts nasal along medial edge only (0), or me-dial and anterior edges (1).

Character 13 (Clark, 1994: char. 13): Nasalcontribution to narial border: yes (0), or no (1).

Character 14 (Clark, 1994: char. 14): Nasal-pre-maxilla contact: present (0), or absent (1).

Character 15 (modified from Clark, 1994: char.15): Descending process of prefrontal: does notcontact palate (0), or contacts palate (1).

Character 16 (Clark, 1994: char. 16): Postorbit-al-jugal contact: postorbital anterior to jugal (0),or postorbital medial to jugal (1), or postorbitallateral to jugal (2).

Character 17 (Clark, 1994: char. 17): Anteriorpart of the jugal with respect to posterior part: asbroad (0), or twice as broad (1).

Character 18 (Clark, 1994: char. 18): Jugal barbeneath infratemporal fenestra: flattened (0), orrod-shaped (1).

Character 19 (Clark, 1994: char. 19): Quadra-tojugal dorsal process: narrow, contacting only asmall part of postorbital (0), or broad, extensivelycontacting the postorbital (1).

Character 20 (Clark, 1994: char. 20): Frontalwidth between orbits: narrow, as broad as nasals(0), or broad, twice as broad as nasals (1).

Character 21 (Clark, 1994: char. 21): Frontals:paired (0), unpaired (1).

Character 22 (Clark, 1994: char. 22): Dorsalsurface of frontal and parietal: flat (0), or withmidline ridge (1).

Character 23 (modified from Clark, 1994: char.23 by Buckley and Brochu, 1999: char. 81): 1Parieto-postorbital suture: absent from dorsal sur-face of skull roof and supratemporal fossa (0),absent from dorsal surface of skull roof but broad-ly present within supratemporal fossa (1), or pre-sent within supratemporal fossa and on dorsal sur-face of skull roof (2).

Character 24 (Clark, 1994: char. 24): Supratem-poral roof dorsal surface: complex (0), or dorsallyflat ‘‘skull table’’ developed, with postorbital andsquamosal with flat shelves extending laterally be-yond quadrate contact (1).

Character 25 (modified from Clark, 1994: char.25) Postorbital bar: sculpted (if skull sculpted)(0), or unsculpted (1).

Character 26 (modified from Clark, 1994: char.26): Postorbital bar: transversely flattened (0), orcylindrical (1).

Character 27 (Clark, 1994: char. 27): Vascularopening in dorsal surface of postorbital bar: ab-sent (0), or present (1).

Character 28 (modified from Clark, 1994: char.28): Postorbital anterolateral process: absent or


poorly developed (0), or well developed, long,and acute (1).

Character 29 (Clark, 1994: char. 29): Dorsalpart of the postorbital: with anterior and lateraledges only (0), or with anterolaterally facing edge(1).

Character 30 (Clark, 1994: char. 30): Dorsalend of the postorbital bar broadens dorsally, con-tinuous with dorsal part of postorbital (0), or dor-sal part of the postorbital bar constricted, distinctfrom the dorsal part of the postorbital (1).

Character 31 (Clark, 1994: char. 31): Bar be-tween orbit and supratemporal fossa broad andsolid, with broadly sculpted dorsal surface (0), orbar narrow, sculpting restriced to anterior surface(1).

Character 32 (modified from Clark, 1994: char.32): Parietal: with broad occipital portion (0), orwithout broad occipital portion (1).

Character 33 (Clark, 1994: char. 33) Parietal:with broad sculpted region separating fossae (0),or with sagittal crest between supratemporal fos-sae (1).

Character 34 (Clark, 1994: char. 34): Postpar-ietal (dermosupraoccipital): a distinct element (0),or not distinct (fused with parietal?) (1).

Character 35 (Clark, 1994: char. 35): Postero-dorsal corner of the squamosal: squared off, lack-ing extra ‘‘lobe’’ (0), or with unsculptured ‘‘lobe’’(1).

Character 36 (modified from Clark, 1994: char.36): Posterolateral process of squamosal: poorlydeveloped and projected horizontally at the samelevel of the skull (0), elongated, thin, and poste-riorly directed, not ventrally deflected (1), or elon-gated, posterolaterally directed, and ventrally de-flected (2).

Character 37. (Clark, 1994: char. 37): 1 Pala-tines: do not meet on palate below the narial pas-sage (0), form palatal shelves that do not meet (1),or meet ventrally to the narial passage, formingpart of secondary palate (2).

Character 38 (Clark, 1994: char. 38): Pterygoid:restricted to palate and suspensorium, joints withquadrate and basisphenoid overlapping (0), orpterygoid extends dorsally to contact laterosphen-oid and form ventrolateral edge of the trigeminalforamen, strongly sutured to quadrate and later-osphenoid (1).

Character 39 (modified from Clark, 1994: char.39): Choanal opening: continuous with pterygoidventral surface except for anterior and anterolat-eral borders (0), or opens into palate through adeep midline depression (choanal groove) (1).

Character 40 (Clark, 1994: char. 40): Palatalsurface of pterygoids: smooth (0), or sculpted (1).

Character 41 (Clark, 1994: char. 41): Ptery-

goids posterior to choanae: separated (0), or fused(1).

Character 42 (modified from Clark, 1994: char.42 by Ortega et al., 2000: char. 139): Depressionon primary pterygoidean palate posterior to cho-ana: absent or moderate in size being narrowerthan palatine bar (0), or wider than palatine bar(1).

Character 43 (Clark, 1994: char. 43): Ptery-goids: do not enclose choana (0), or enclose cho-ana (1).

Character 44 (modified from Clark, 1994: char.44): Anterior edge of choanae situated near pos-terior edge of suborbital fenestra (or anteriorly)(0), or near posterior edge of pterygoid flanges(1).

Character 45 (Clark, 1994: char. 45): 1 Quad-rate: without fenestrae (0), with single fenestrae(1), or with three or more fenestrae on dorsal andposteromedial surfaces (2).

Character 46 (Clark, 1994: char. 46): Posterioredge of quadrate: broad medial to tympanum,gently concave (0), or posterior edge narrow dor-sal to otoccipital contact, strongly concave (1).

Character 47 (Clark, 1994: char. 47): Dorsal,primary head of quadrate articulates with squa-mosal, otoccipital, and prootic (0), or with prooticand laterosphenoid (1).

Character 48 (Clark, 1994: char. 48): Ventro-lateral contact of otoccipital with quadrate: verynarrow (0), or broad (1).

Character 49 (Clark, 1994: char. 49): 1 Quad-rate, squamosal, and otoccipital: do not meet toenclose cranioquadrate passage (0), enclose pas-sage near lateral edge of skull (1), or meet broadlylateral to the passage (2).

Character 50 (Clark, 1994: char. 50): Pterygoidramus of quadrate: with flat ventral edge (0), orwith deep groove along ventral edge (1).

Character 51 (Clark, 1994: char. 51): Ventro-medial part of quadrate: does not contact otoccip-ital (0), or contacts otoccipital to enclose carotidartery and form passage for cranial nerves IX–XI(1).

Character 52 (Clark, 1994: char. 52): Eustachi-an tubes: not enclosed between basioccipital andbasisphenoid (0), or entirely enclosed (1).

Character 53 (Clark, 1994: char. 53): Basisphe-noid rostrum (cultriform process): slender (0), ordorsoventrally expanded (1).

Character 54 (Clark, 1994: char. 54): Basipter-ygoid process: prominent, forming movable jointwith pterygoid (0), or basipterygoid process smallor absent, with basisphenoid joint suturally closed(1).

Character 55 (modified from Clark, 1994: char.55 by Ortega et al., 2000: char. 68): Basisphenoidventral surface: shorter than the basioccipital (0),


or wide and similar to, or longer in length thanbasioccipital (1).

Character 56 (Clark, 1994: char. 56): Basisphe-noid: exposed on ventral surface of braincase (0),or virtually excluded from ventral surface by pter-ygoid and basioccipital (1).

Character 57 (Clark, 1994: char. 57): Basioc-cipital: without well-developed biltaeral tuberosi-ties (0), or with large pendulous tubera (1).

Character 58 (Clark, 1994: char. 58): Otoccip-ital: without laterally concave descending flangeventral to subcapsular process (0), or with flange(1).

Character 59 (Clark, 1994: char. 59): Cranialnerves IX–XI: pass through common large fora-men vagi in otoccipital (0), or cranial nerve IXpasses medial to nerves X and XI in separate pas-sage (1).

Character 60 (Clark, 1994: char. 60): Otoccip-ital: without large ventrolateral part ventral to par-occipital process (0), or with large ventrolateralpart (1).

Character 61 (Clark, 1994: char. 61): Crista in-terfenestralis between fenestrae pseudorotundaand ovalis nearly vertical (0), or horizontal (1).

Character 62 (Clark, 1994: char. 62): Supraoc-cipital: forms dorsal edge of the foramen magnum(0), or otoccipitals broadly meet dorsal to the fo-ramen magnum, separating supraoccipital fromforamen (1).

Character 63 (Clark, 1994: char. 63): Mastoidantrum: does not extend into supraoccipital (0), orextends through transverse canal in supraoccipitalto connect middle ear regions (1).

Character 64 (Clark, 1994: char. 64): Posteriorsurface of supraoccipital: nearly flat (0), or withbilateral posterior prominences (1).

Character 65 (modified from Clark, 1994: char.65): 1 One small palpebral present in orbit (0),one large palpebral (1), or two large palpebrals(2).

Character 66 (Clark, 1994: char. 66): Externalnares: divided by a septum (0), or confluent (1).

Character 67 (Clark, 1994: char. 67): 1 Antor-bital fenestra: as large as orbit (0), about half thediameter of the orbit (1), much smaller than theorbit (2), or absent (3).

Character 68 (modified from Clark, 1994: char.68 by Ortega et al., 2000: char. 41): Supratem-poral fenestrae extension: relatively large, cover-ing most of surface of skull roof (0), or relativelyshort, fenestrae surrounded by a flat and extendedskull roof (1).

Character 69 (modified from Clark, 1994: char.69): 1 Choanal groove: undivided (0), partiallyseptated (1), or completely septated (2).

Character 70 (Clark, 1994: char. 70): Dentary:

extends posteriorly beneath mandibular fenestra(0), or does not extend beneath fenestra (1).

Character 71 (modified from Clark, 1994: char.71): Retroarticular process: absent or extremelyreduced (0), very short, broad, and robust (1),with an extensive rounded, wide, and flat (orslightly concave) surface projected posteroven-trally and facing dorsomedially (2), posteriorlyelongated, triangular-shaped and facing dorsally(3), or posteroventrally projecting and paddle-shaped (4).

Character 72 (Clark, 1994: char. 72): Prearti-cular: present (0), or absent (1).

Character 73 (modified from Clark, 1994: char.73): 1 Articular without medial process (0), withshort process not contacting braincase (1), or withprocess articulating with otoccipital and basisphe-noid (2).

Character 74 (Clark, 1994: char. 74): Dorsaledge of surangular: flat (0), or arched dorsally (1).

Character 75 (Clark, 1994: char. 75): Mandib-ular fenestra: present (0), or absent (1).

Character 76 (Clark, 1994: char. 76): Insertionarea for M. pterygoideous posterior: does not ex-tend onto lateral surface of angular (0), or extendsonto lateral surface of angular (1).

Character 77 (modified from Clark, 1994: char.77): 1 Splenial involvement in symphysis in ven-tral view: not involved (0), involved slightly insymphysis (1), or extensively involved (2).

Character 78 (Clark, 1994: char. 78): Posteriorpremaxillary teeth: similar in size to anterior teeth(0), or much longer (1).

Character 79 (modified from Clark, 1994: char.79): 1 Maxillary teeth waves: absent, no toothsize variation (0), one wave of teeth enlarged (1),or enlarged maxillary teeth curved in two waves(‘‘festooned’’) (2).

Character 80 (Clark, 1994: char. 80): Anteriordentary teeth opposite premaxilla-maxilla contact:no more than twice the length of other dentaryteeth (0), or more than twice the length (1).

Character 81 (modified from Clark, 1994: char.81): Dentary teeth posterior to tooth opposite pre-maxilla-maxilla contact: equal in size (0), or en-larged dentary teeth opposite to smaller teeth inmaxillary toothrow (1).

Character 82 (modified from Clark, 1994: char.82 by Ortega et al., 2000: char. 120): Anterior andposterior scapular edges: symmetrical in lateralview (0), anterior edge more strongly concavethan posterior edge (1), or dorsally narrow withstraight edges (2).

Character 83 (modified from Clark, 1994: char.83 by Ortega et al., 2000: char. 121): Coracoidlength: up to two-thirds of the scapular length (0),or subequal in length to scapula (1).

Character 84 (Clark, 1994: char. 84): Anterior


process of ilium: similar in length to posteriorprocess (0), or one-quarter or less of the length ofthe posterior process (1).

Character 85 (Clark, 1994: char. 85): Pubis:rodlike without expanded distal end (0), or withexpanded distal end (1).

Character 86 (Clark, 1994: char. 86): Pubis:forms anterior half of ventral edge of acetabulum(0), or pubis at least partially excluded from theacetabulum by the anterior process of the ischium(1).

Character 87 (Clark, 1994: char. 87): Distal endof femur: with large lateral facet for the fibula (0),or with very small facet (1).

Character 88 (Clark, 1994: char. 88): Fifth ped-al digit: with phalanges (0), or without phalanges(1).

Character 89 (Clark, 1994: char. 89): Atlas in-tercentrum: broader than long (0), or as long asbroad (1).

Character 90 (modified from Clark, 1994: char.90): 1 Cervical neural spines: all anteroposteri-orly large (0), only posterior ones rodlike (1), orall spines rodlike (2).

Character 91 (modified from Clark, 1994: char.91 by Buscalioni and Sanz, 1988: char. 37 and byBrochu, 1997a: char. 7): 1 Hypapophyses in cer-vicodorsal vertebrae: absent (0), present only incervical vertebrae (1), present in cervical and thefirst two dorsal vertebrae (2), present up to thethird dorsal vertebra (3), or present up to thefourth dorsal vertebrae (4).

Character 92 (Clark, 1994: char. 92): Cervicalvertebrae: amphicoelous or amphyplatian (0), orprocoelous (1).

Character 93 (Clark, 1994: char. 93): Trunk ver-tebrae: amphicoelous or amphyplatian (0), or pro-coelous (1).

Character 94 (Clark, 1994: char. 94): All caudalvertebrae: amphicoelous or amphyplatian (0), firstcaudal biconvex with other procoelous (1), or pro-coelous (2).

Character 95 (Clark, 1994: char. 95): Dorsal os-teoderms: rounded or ovate (0), or rectangular,broader than long (1), or square (2).

Character 96 (modified from Clark, 1994: char.96, and Brochu, 1997a: char. 40): 1 Dorsal os-teoderms: without articular anterior process (0),with a discrete convexity on anterior margin (1),or with a well-developed process located antero-laterally in dorsal parasagittal osteoderms (2).

Character 97 (modified from Clark, 1994: char.97 by Ortega et al., 2000: chars. 107 and 108): 1Rows of dorsal osteoderms: two parallel rows (0),more than two (1), or more than four with ‘‘ac-cessory ranges of osteoderms’’ (sensu Frey, 1988)(2).

Character 98 (Clark, 1994: char. 98): Osteo-

derms: some or all imbricated (0), or sutured toone another (1).

Character 99 (Clark, 1994: char. 99): Tail os-teoderms: dorsal only (0), or completely sur-rounded by osteoderms (1).

Character 100 (Clark, 1994: char. 100): Trunkosteoderms: absent from ventral part of the trunk(0), or present (1).

Character 101 (Clark, 1994: char. 101): Osteo-derms: with longitudinal keels on dorsal surfaces(0), or without longitudinal keels (1).

Character 102 (Wu and Sues, 1996: char. 14):Jugal: participating in margin of antorbital fossa(0), or separated from it (1).

Character 103 (modified from Wu and Sues,1996: char. 23): 1 Articular facet for quadratecondyle: equal in length to the quadrate condyles(0), slightly longer (1), or close to three times thelength of the quadrate condyles (2).

Character 104 (modified from Wu and Sues,1996: char. 24 and Wu et al., 1997: char. 124): 1Jaw joint: placed at level with basioccipital con-dyle (0), below basioccipital condyle about abovelevel of lower toothrow (1), or below level oftoothrow (2).

Character 105 (modified from Wu and Sues,1996: char. 27 and Ortega et al., 2000: char. 133):1 Premaxillary teeth: five (0), four (1), three (2),or two (3).

Character 106 (modified from Wu and Sues,1996: char. 29): Unsculptured region along alve-olar margin on lateral surface of maxilla: absent(0), or present (1).

Character 107 (Wu and Sues, 1996: char. 30):1 Maxilla: with eight or more teeth (0), seven (1),six (2), five (3), or four teeth (4).

Character 108 (Wu and Sues, 1996: char. 33):Coracoid: without posteromedial or ventromedialprocess (0), with elongate posteromedial process(1), or distally expanded ventromedial process (2).

Character 109 (Wu and Sues, 1996: char. 40):Radiale and ulnare: short and massive (0), orelongate (1).

Character 110 (Wu and Sues, 1996: char. 41):Postacetabular process: directed posteroventrallyor posteriorly (0), or directed posterodorsally andmuch higher in position than preacetabular pro-cess (1).

Character 111 (modified from Gomani, 1997:char. 4): Prefrontals anterior to orbits: elongated,oriented parallel to anteroposterior axis of theskull (0), or short and broad, oriented postero-medially-anterolaterally (1).

Character 112 (modified from Gomani, 1997:char. 32): Basioccipital and ventral part of otoc-cipital: facing posteriorly (0), or posteroventrally(1).

Character 113 (Buscalioni and Sanz, 1988:


char. 35): Vertebral centra: cylindrical (0), orspool shaped (1).

Character 114 (modified from Buscalioni andSanz, 1988: char. 39): Transverse process of pos-terior dorsal vertebrae dorsoventrally low andlaminar (0), or dorsoventrally high (1).

Character 115 (Buscalioni and Sanz, 1988:char. 44): Number of sacral vertebrae: two (0), ormore than two (1).

Character 116 (Buscalioni and Sanz, 1988:char. 49): Supra-acetabular crest: present (0), orabsent (1).

Character 117 (Buscalioni and Sanz, 1988:char. 54): Proximal end of radiale expanded sym-metrically, similarly to the distal end (0), or moreexpanded proximomedially than proximolaterally(1).

Character 118 (Ortega et al., 1996: char. 5):Lateral surface of the dentary: without a longitu-dinal depression (0), or with a longitudinal de-pression (1).

Character 119 (Ortega et al., 1996: char. 9):Ventral exposure of splenials: absent (0), or pre-sent (1).

Character 120 (Ortega et al., 1996: char. 11,2000: char. 100): Tooth margins: with denticulatecarinae (0), or without carinae or with smooth orcrenulated carinae (1).

Character 121 (modified from Pol, 1999a: char.133 and Ortega et al., 2000: char. 145): Lateralsurface of anterior process of jugal: flat or convex(0), or with broad shelf below the orbit with tri-angular depression underneath it (1).

Character 122 (Pol, 1999a: char. 134): Jugal:does not exceed the anterior margin of orbit (0),or exceeds margin (1).

Character 123 (Pol, 1999a: char. 135): Notch inpremaxilla on lateral edge of external nares: ab-sent (0), or present on the dorsal half of the ex-ternal nares lateral margin (1).

Character 124 (Pol, 1999a: char. 136): Dorsalborder of external nares: formed mostly by thenasals (0), or by both the nasals and premaxilla(1).

Character 125 (Pol, 1999a: char. 138): Poster-odorsal process of premaxilla: absent (0), or pre-sent extending posteriorly wedging between max-illa and nasals (1).

Character 126 (Pol, 1999a: char. 139 and Or-tega et al., 2000: char. 9): 1 Premaxilla-maxillasuture in palatal view, medial to alveolar region:anteromedially directed (0), sinusoidal, postero-medially directed on its lateral half and antero-medially directed along its medial region (1), orposteromedially directed (2).

Character 127 (Pol, 1999a: char. 140): Nasallateral border posterior to external nares: laterallyconcave (0), or straight (1).

Character 128 (Pol, 1999a: char. 141): Nasallateral edges: nearly parallel (0), oblique to eachother converging anteriorly (1), or oblique to eachother diverging anteriorly (2).

Character 129 (Pol, 1999a: char. 143): Palatineanteromedial margin: exceeding the anterior mar-gin of the palatal fenestrae wedging between themaxillae (0), or not exceeding the anterior marginof palatal fenestrae (1).

Character 130 (Pol, 1999a: char. 144): Dorso-ventral height of jugal antorbital region respect toinfraorbital region: equal or lower (0), or antor-bital region more expanded than infraorbital re-gion of jugal (1).

Character 131 (Pol, 1999a: char. 145): Maxilla-lacrimal contact: partially included in antorbitalfossa (0), or completely included (1).

Character 132 (Pol, 1999a: char. 146): Lateraleustachian tube openings: located posteriorly tothe medial opening (0), or aligned anteroposteri-orly and dorsoventrally (1).

Character 133 (Pol, 1999a: char. 147): Anteriorprocess of ectopterygoid: developed (0), or re-duced–absent (1).

Character 134 (Pol, 1999a: char. 148): Posteriorprocess of ectopterygoid: developed (0), or re-duced-absent (1).

Character 135 (Pol, 1999a: char. 149 and Or-tega et al., 2000: char. 13): Small foramen locatedin the premaxillo-maxillary suture in lateral sur-face (not for big mandibular teeth): absent (0), orpresent (1).

Character 136 (Pol, 1999a: char. 150): Jugalposterior process: exceeding posteriorly the infra-temporal fenestrae (0), or not (1).

Character 137 (Pol, 1999a: char. 151): Com-pressed crown of maxillary teeth: oriented parallelto the longitudinal axis of skull (0), or obliquelydisposed (1).

Character 138 (Pol, 1999a: char. 152): Largeand aligned neurovascular foramina on lateralmaxilary surface: absent (0), or present (1).

Character 139 (modified from Pol, 1999a: char.153): External surface of maxilla and premaxilla:with a single plane facing laterally (0), or withventral region facing laterally and dorsal regionfacing dorsolaterally (1).

Character 140 (Pol, 1999a: char. 154 and Or-tega et al., 2000: char. 104): Maxillary teeth: notcompressed laterally (0), or compressed laterally(1).

Character 141 (Pol, 1999a: char. 155): Poster-oventral corner of quadratojugal: reaching thequadrate condyles (0), or not reaching the quad-rate condyles (1).

Character 142 (Pol, 1999a: char. 156): Base ofpostorbital process of jugal: directed posterodor-sally (0), or dorsally (1).


Character 143 (Pol, 1999a: char. 157): 1 Post-orbital process of jugal: anteriorly placed (0), inthe middle (1), or posteriorly positioned (2).

Character 144 (Pol, 1999a: char. 158 and Or-tega et al., 2000: char. 36): Postorbital-ectoptery-goid contact: present (0), or absent (1).

Character 145 (Pol, 1999a: char. 161): Quad-ratojugal: not ornamented (0), or ornamented inthe base (1).

Character 146 (Pol, 1999a: char. 162): Prefron-tal-maxillary contact in the inner anteromedial re-gion of orbit: absent (0), or present (1).

Character 147 (Pol, 1999a: char. 163): Basi-sphenoid: without lateral exposure (0), or with lat-eral exposure on the braincase (1).

Character 148 (Pol, 1999a: char. 165): Quadrateprocess of pterygoids: well developed (0), orpoorly developed (1).

Character 149 (modified from Pol, 1999a: char.166 and Ortega et al., 2000: char. 44): 1 Quadratemajor axis directed: posteroventrally (0), ventrally(1), or anteroventrally (2).

Character 150 (Pol, 1999a: char. 167): Quadratedistal end: with only one plane facing posteriorly(0), or with two distinct faces in posterior view, aposterior one and a medial one bearing the fora-men aereum (1).

Character 151 (Pol, 1999a: char. 168): Antero-posterior development of neural spine in axis:well developed covering all the neural arch length(0), or poorly developed, located over the poste-rior half of the neural arch (1).

Character 152 (Pol, 1999a: char. 169): Prezy-gapophyses of axis: not exceeding anterior edgeof neural arch (0), or exceeding the anterior mar-gin of neural arch (1).

Character 153 (Pol, 1999a: char. 170): Postzy-gapophyses of axis: well developed, curved lat-erally (0), or poorly developed (1).

Character 154 (modified from Pol, 1999b: char.212): Shape of dentary symphysis in ventral view:tapering anteriorly forming an angle (0), U-shaped, smoothly curving anteriorly (1), or lateraledges longitudinally oriented, convex anterolat-eral corner, and extensive transversaly orientedanterior edge (2).

Character 155 (Pol, 1999b: char. 213): Un-sculpted region in the dentary below the toothrow: absent (0), or present (1).

Character 156 (Ortega et al., 1996: char. 13 andBuckley et al., 2000: char. 117): Cheek teeth: notconstricted at base of crown (0), or constricted(1).

Character 157 (Ortega et al., 2000: char. 42):Outer surface of squamosal laterodorsally orient-ed: extensive (0), or reduced and sculpted (1), orreduced and unsculpted (2).

Character 158 (Ortega et al., 2000: char. 74):

Length/height proportion of infratemporal fenes-tra: higher than long or subequal (0), or very an-teroposteriorly elongated (1).

Character 159 (Ortega et al., 2000: char. 90):Foramen intramandibularis oralis: small or absent(0), or big and slotlike (1).

Character 160 (Ortega et al., 2000: char. 146):Ectopterygoid medial process: single (0), orforked (1).

Character 161 (modified from Gomani, 1997:char. 46 and Buckley et al., 2000: char. 113):Cusps of teeth: unique cusp (0), one main cuspwith smaller cusps arranged in one row (1), onemain cusp with smaller cusps arranged in morethan one row (2), several cusps of equal size ar-ranged in more than one row (3), or multiplesmall cusps along edges of occlusal surface (4).

Character 162 (Pol and Norell, 2004: char.164): Cross section of distal end of quadrate: me-diolaterally wide and anteroposteriorly thin (0), orsubquadrangular (1).

Character 163 (Pol and Norell, 2004: char.165): Palatine-pterygoid contact on palate: pala-tines overlie pterygoids (0), or palatines firmly su-tured to pterygoids (1).

Character 164 (Wu et al., 1997: char. 103):Squamosal descending process: absent (0), or pre-sent (1).

Character 165 (modified from Wu et al., 1997:char. 105): 1 Development of distal quadratebody ventral to otoccipital-quadrate contact: dis-tinct (0), incipiently distinct (1), or indistinct (2).

Character 166 (Wu et al., 1997: char. 106):Pterygoid flanges: thin and laminar (0), or dor-soventrally thick, with pneumatic spaces (1).

Character 167 (Wu et al., 1997: char. 108):Postorbital participation in infratemporal fenestra:almost or entirely excluded (0), or bordering in-fratemporal fenestra (1).

Character 168 (Wu et al., 1997: char. 109): Pal-atines: form margin of suborbital fenestra (0), orexcluded from margin of suborbital fenestra (1).

Character 169 (Wu et al., 1997: char. 110): An-gular posterior to mandibular fenestra: widely ex-posed on lateral surface of mandible (0), or shift-ed to the ventral surface of mandible (1).

Character 170 (Wu et al., 1997: char. 112): Pos-teroventral edge of mandibular ramus: straight orconvex (0), or markedly deflected (1).

Character 171 (modified from Wu et al., 1997:char. 119): Quadrate ramus of pterygoid in ventralview: narrow (0), or broad (1).

Character 172 (Wu et al., 1997: char. 121):Pterygoids: not in contact anterior to basisphenoidon palate (0), or pterygoids in contact (1).

Character 173 (Wu et al., 1997: char. 122):Olecranon: well developed (0), or absent (1).

Character 174 (Wu et al., 1997: char. 123): Cra-


nial table width respect to ventral portion of skull:as wide as ventral portion (0), or narrower thanventral portion of skull (1).

Character 175 (Wu et al., 1997: char. 127): De-pression on posterolateral surface of maxilla: ab-sent (0), or present (1).

Character 176 (Wu et al., 1997: char. 128): An-terior palatal fenestra: absent (0), or present (1).

Character 177 (Pol and Norell, 2004: char.179): Paired ridges located medially on ventralsurface of basisphenoid: absent (0), or present (1).

Character 178 (Pol and Norell, 2004: char.180): Posterolateral end of quadratojugal: acute orrounded, tightly overlapping the quadrate (0), orwith sinusoidal ventral edge and wide and round-ed posterior edge slightly overhanging the lateralsurface of the quadrate (1).

Character 179 (Pol and Norell, 2004: char.181): Orientation of quadrate body distal to otoc-cipital-quadrate contact in posterior view: ven-trally (0), or ventrolaterally (1).

Character 180 (Gasparini et al., 1993: char. 3):Wedgelike process of the maxilla in lateral surfaceof premaxilla-maxilla suture: absent (0), or pre-sent (1).

Character 181: Palpebrals: separated from thelateral edge of the frontals (0), or extensively su-tured to each other and to the lateral margin ofthe frontals (1).

Character 182: External surface of ascendingprocess of jugal: exposed laterally (0), or exposedposterolaterally (1).

Character 183: Longitudinal ridge on lateralsurface of jugal below infratemporal fenestra: ab-sent (0), or present (1).

Character 184: Dorsal surface of posterolateralregion of squamosal: without ridges (0), or withthree curved ridges oriented longitudinally (1).

Character 185: Ridge along dorsal section ofquadrate-quadratojugal contact: absent (0), or pre-sent (1).

Character 186: Sharp ridge along the ventralsurface of angular: absent (0), or present (1).

Character 187: Longitudinal ridge along thedorsolateral surface of surangular: absent (0), orpresent (1).

Character 188: Dorsal surface of osteodermsornamented with anterolaterally and anteromedi-ally directed ridges (fleur de lys pattern of Os-molska et al., 1997): absent (0), or present (1).

Character 189: Cervical region surrounded bylateral and ventral osteoderms sutured to the dor-sal elements: absent (0), or present (1).

Character 190: Appendicular osteoderms: ab-sent (0), or present (1).

Character 191 (Ortega et al., 2000: character72): Supratemporal fenestra: present (0), or absent(1).

Character 192 (Pol and Norell, 2004: char.183): Choanal opening: opened posteriorly andcontinuous with pterygoid surface (0), or closedposteriorly by an elevated wall formed by thepterygoids (1).

APPENDIX 2

DATA MATRIX USED IN PHYLOGENETIC ANALYSIS

Gracilisuchus stipanicicorum000000??0?000000000000?0?000000000?0??0?0?00000?000???0000?0???00000?100000?00000000?0???0000?0?000001012?00?00????0?01?01000??1?01???000001002?0???0000?????0??0??0000?00000?0?00000000?0?00000

Terrestrisuchus gracilis000??00??0??000000?000?0?00?000?110?00000?00000?000??0?000?000????00???010??0?000000?010?0000?0200000101??01100??00000?00100??10?00?110?0?0??[01]110???00000????00?0??0????00??0?0???0???????????00

Dibothrosuchus elaphros000?00?020??001???000000??????00110000000?00000?0000?00000?0?0101000?010100?0010?000?????2000?0?????01010?01100?0?00000001001?10?00?1?000101011100??000001??00000010001000100?0?00000000?0000000

Protosuchus richardsoni2100000120?00001101000210000010001000101

0?00201001111110010101102011?110210001010100011100[1234]00?120011010111021001010000[01]000000?01??01??10010[01]0101000000???0100000000120000011110??01000?010?00000

Hemiprotosuchus leali?00?00?10??????10010?0??00?0010?11?0??01??0020?00?11?1100101??1?2?11??1?21????01?????????0????1200?1?101??0??????????000?000??10?00???00000??10?????00???????0?000?12???001??10?0?00?01??00???00

Orthosuchus stormbergi21100001201?0001001000[01]10000010001000?000?002011001111100??1?1?02011?0?0?0?001000100011100000?120010010211421001?10010?100000001?01010000000000?0???00001???000000?12?000011110?001000?0?000?000

Kayenta form[12]01110?1200000?10010?0??00????0?0???11110?002010011111100001011?2011?0102100?1010??0????00??0?1200101101112?????0????0110


0?00?01000111?101001?01?10000000011?0??40012??00011??0?00???00????????0

Zaraasuchus shepardi10?????????????1?01?01?1000001?10?02????????????????????????????2?????1??010??????????????[1234]0??1010??0???????????0??????????????????????0?????1??1?????????1?00????????1?00???0??????11111111111?

Gobiosuchus kielanae101000?110000011001?[01][01]?1?00001?10?0201000?0020112011111000?1????201???1?20100[01]010?0?1???????0?1010110[01]012002??0000???0010[01]00001000000?00001001211?0000???110000000?121000011?00?0?00111111111110

Sichuanosuchus shuhanensis[12]01??0?1200[01]00?10010[01]1?110???1?00?021?10?00020?1?011?1100???????2?11????1?000011?1??1?????000????????1?11?0?1????0??100100??1??10?0????00111[01]1210??00?????1?????010111011111100?110000100?1???00

Shantungosuchus hangjinensis2?1????1?0???0?1??1????11??????????21?1[01]100020?1?011?1100?10????????101?1?000??10???????0??????????????1???????1?????0010???????00??10?00??111211??001?????0?0?00????1011111??0?110??0???1?????0

Zosuchus davidsoni201??0?1200000??001010[01]110?001110?02211010012?1??011?11000?0?1?0211110????0?01111????????????????????1?12?3????1?????00100011011?0001?0?0010112?[01]?0001???0?00???010111??1011?10111000000100???00

Fruita form201??001200100010000100100000110010221?11?0020112?1???0?0??0??1?2?31?????1?0111101011?1?00011112?0??1???[01]00???1?1001?001?0?0100100??101?0011?01110??0??00?10?0000?1???000????101?0?00000?000??0?

Hsisosuchus chungkingensis211??????1??000000100001100011000?0221101000[12]??12?11?10000?0?1?0??111?4?00[01]02?1??10???????000?1000???101?0021??1?????01001???????0000??00??1?11?1??00????????0??0????10?0?0111[01]?00??00?0?1000?01

Notosuchus terrestris101?001101010011100011111100110001022110110021112011?1000010?1102111112?0101110001[01]111?1?200001000??0122011???1100101[01]1101[01]010010000001111111111?00011110010000101110110000111011000000000000001

Comahuesuchus brachybuccalis103??0?101??00?????0112????????0010?2????1??11?1?????????????????131??????0?10101???????????????????????[01]13???1??????0?10?101201

?01?????011??0?1????11???11?00100?1?0??000???100??0?000??0????0?

Uruguaysuchus aznarezi201?001101??00??10??1??1????1???01022?101?0011????1?????0??0???01111[12]???000110100??1?1??????0000?0??01?21002100?00?000?[01]???01?1?00????1?0111?11?????11?????1?0001????????0???10?????00????????01

Simosuchus clarki10301011000000100010111110?0110001021?10100011?11011?1000010?1?020112121010110000???????02100?2010?10002010???01??????11011012120000101001110021100120???211[12]0001111011001[01]1?1000000000001000001

Malawisuchus mwakayasyunguti101?00?1110000?[01]10001[01][01]1100?110001?22110100011??20???1000?10?1?02?111[01]2?0101110001????1??210000010??01[12]2111???01?0???01100101?11000???110110101?0?0001???0?100??21110?100001110000000000000???01

Candidodon itapecurense???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????1????????????????0??0???????????????1????2???????????????????????????????

Chimaerasuchus paradoxus101?0001111?00???????????????????????????????????????????????????12??0110?01010??1?1?????2100?00????11[12]?314210??00?0100111111011??????0?0110??????????10?11?????3???????????1?00???0??????????0?

Sphagesaurus huenei101?000101??00??100?????110?????????21101?00?????011?1000????????13?2????????100????????1???????????????312????0???????11111101111111111111110011101111?0?11?0??011?0?10??01??000000?00???????01

Baurusuchus pachecoi100??0?121??00?1101????111?0110?????2?10110011112011?1000?10??10??311121010111111?????????????????????12103????1?????1101110101011100110011110110?0111???[01]0[01]1111011101?00001?00010000000000???01

Bretesuchus bonapartei1[01]0??01121??00???????????0??????????2???10011????????1011?1??????13?1??1?00?10110???????????????????????100????1???????01??0????01??0???0??1?0???????????[01]0[01]?1?10?1???1??001??00??????????0????1

Iberosuchus macrodon1?0?00012?0?00111000111111?01?000?02??10100111?12??1?101??10?1????111??10?0?1011011??????[12][1234]00??00???00?[12][01]0?2??000


0???11001101010?1?0??100?11001?0??101???[01]?0111?001101?0??01?100001000000??0??01

Araripesuchus gomesii201000110100001110001011111011[01]001022110100011112011?10000?0?110201121210001101[01][01]1[01]11111?1[234]000100010011110021001001010100100100100000010011000210000110?0011[01]0000111101000011100?000000000000001

Araripesuchus patagonicus201000?1010000?1[01]000101111?0111001022?10100011?12?11?1000??0?1?02?11212?0?011[01]1??1?1??????????1000??0111100???01???0?01?01101?010000??100110102?0??01????0??[01]1000111?0100001110?0000000000000001

Lomasuchus palpebrosus201????1211?00?11000101111??110001022?1010001??12??1?100??1??1??2?21?????00??0[12]11????????????????????1???00???00?????0?00???1?110?00???00011?0??1??0??????010???0?11??10??01?1000??11000??0???01

Peirosaurus tormini201?011??1??00??????10?1????????0???2?10???????????????????????????1??????????[12]1????????????????????????000????????????0????1???0???????0?1??????????????[01]??????0??????????????00??1??????????0?

Theriosuchus pusillus20110111110100110000110111100110011?211010001?11?01111000?????1?20211?41001010101101111100011112001001010002?00?10?110110[01]001?1100?00?0?00100??01??0?00??10100000?11?010??01?10000??0000??????01

Alligatorium?0??????1?0000?1000010?111??0?100?1????0??00??11??1??1000???????20?1????00101?101?011111000???1?00100???????????10??1???????????????????0???????????????????????0??????????????????0????????????

Pelagosaurus typus202?1111110011020101000000000000[01]100211010000001101111001001?10001200?30000020000110111?0000001200011101?00???10???????1?1??????0000??010010?0010???00????0001000011201000011000001?0000000???01

Teleosauridae[02]02?1111110011020100100000000000110021?01000?001101111001011?1?00120003?000?200002101111?0000?12000101011?0???10??01001101??1011000011000010100?0??0000??10001000011?010?01110001010000000000001

Metriorhynchidae[02]02?12110100111201011000?0000000110021?0?000?001101111001011?1?001200?300010200

002101?11?0000??????0??012?0???100?01001101??1011?000??000010102?0???000????001000011?01000?1100000100000000???01

Sokotosuchus ianwilsoni2?2???1101??10????001001???101001?012?1??????1112?11?1?11??0???1?1?0?????????01????????????????????????????????????????1????????????????0??0????????????????????0???????????????????????????????

Dyrosauridae002??1?101?010?11?00100011?1010011012?10101001112011?1011?10?10101302?3?00??2?000????????0?00??????1???????????????????1????????????????0??0???????????????021?0001????0??????00??1?0000000???01

Pholidosaurus decipiens212?111101??11?11101100111?00100010?211?100001112111?101??10?100?1311?300???2?0???11?1???0??0??2?0?????????????????????1????1?110?????0?0010???????????????0?1?0001???10?001?100?010???0??????01

Goniopholis203?1211110010111000100111?0010001002?101000?1112011?1010?10?1?021312?4100[01]0[12]02011?1??1??0?00?1200?11?000002100010?1101100??101100?000010010001?1???0000110020000011001000011110?010000000000001

Eutretauranosuchus delfsi203????1?10010111000100111?00?0001001110?000?1112011?1010??0?1?0?121204?00001020111???1??0??0?1?????????000???00?????0?100????110???????0??00???1???0????10?2???001?0??000?1?110?01?0000000???01

Bernissartia fagessi203??21111??00111000?00111?001000?002?????0001112?11?10100?0?1???1?1??410010102011?1?11??020021110110100000??00????????1????1????????0??0?10???01???0????1?12000001????0??????00??10000????0??01

Hylaeochampsa vectiana00???????11???11????1?01???0????0?002?1?1011?????????101??1??1?????10??????????????????????????????????????????0???????10????????????0??0??????0????????????2??00?????????????????????????????01

Borealosuchus formidabilis203?1211110010111000100111?001000100211010111111211111010010?110?1310031000110?011111111113111?110?00?000002110?100100?101??11110??000000010001?1???0000110?20?000110010000111000010000000000001

Gavialis gangeticus212?121111001111110110111110010001002110101101112011110110101110[01]1310031000120


00001111110131112111100?000002110?100100?101??121100?00000001000101?1?00001?0?20?00011001000011100001?000000000001

Crocodylus niloticus203012111100[01]011100010211110010001002110?01111112011110100101110[01]131003100010010121111110131112021100?00000211001001

00?101??121100?0000000100110101100001?0?200000110010000111000010000000000001Alligator mississippiensis203112?101?0001110001021111001000?002110101111112011110100101110[01]0312031000100201211111111311120211?0?00000211001001001101??111000?00000001001[12]01011000011[01]1200000110010000111000010000000000001

APPENDIX 3

FOSSIL TAXA USED IN PHYLOGENETIC ANALYSIS

Collection numbers of the specimens that werefirst-hand revised by the authors are added afterthe bibliographic reference.

Gracilisuchus stipanicicorum (Romer, 1972)Terrestrisuchus gracilis (Crush, 1984)Dibothrosuchus elpahros (Wu and Chatterjee,

1993; IVPP V 7907)Protosuchus richardsoni (Colbert and Mook,

1951; AMNH 3024, MCZ 6727, UCMP130860, 131827)

Hemiprotosuchus leali (Bonaparte, 1971; PVL3829)

Kayenta Form (Clark, 1986; UCMP 97638,125359, 125871)

Orthosuchus stormbergi (Nash, 1975; SAM-K409)

Gobiosuchus kielanae (Osmolska, 1972; ZPALMgR-II/67–71)

Zaraasuchus shepardi (IGM 100/1321)Shantungosuchus hangjinensis (Wu et al., 1994b)Sichuanosuchus shuhanensis (Wu et al., 1997;

IVPP V 10594)Zosuchus davidsoni (Pol and Norell, 2004; IGM

100/1304–1308)Fruita Form (Clark, 1985, 1994; LACM 120455a)Hsisosuchus chungkingensis (Young and Chow,

1953; Li et al., 1994; Wu et al., 1994a; cast ofCNM V 1090)

Notosuchus terrestris (Gasparini, 1971; MACN-RN 1037, 1040, 1041)

Comahuesuchus brachybuccalis (Bonaparte,1991; MUC-PV 202, MACN-N 30–31, MOZ P6131)

Uruguaysuchus aznarezi (Rusconi, 1933)Chimaeresuchus paradoxus (Wu and Sues, 1996;

IVPP V8274)Malawisuchus mwakayasyunguti (Clark et al.,

1989; Gomani, 1997; MAL 45, 49)Candidodon itapecurense (Carvalho, 1994)Simosuchus clarki (Buckley et al., 2000; UA

8679)Sphagesaurus huenei (Price, 1950; Pol, 2003;

RCL 100)

Araripesuchus gomesii (Price, 1959; AMNH24450)

Araripesuchus patagonicus (Ortega et al., 2000;MUC-PV 269, 270)

Baurusuchus pachecoi (Price, 1945; DGM 299-R)Bretesuchus bonapartei (Gasparini et al., 1993;

PVL 4735)Iberosuchus macrodon (Antunes, 1975; Ortega et

al., 2000)Lomasuchus palpebrosus (Gasparini et al., 1991;

MOZ 4084 PV)Peirosaurus tormini (Price, 1955; Gasparini et al.,

1991; MOZ 1750 PV)Theriosuchus pusillus (Owen, 1879; Clark, 1986,

1994; Ortega et al., 2000)Alligatorium (Wellnhofer, 1971; Clark, 1986,

1994)Eutretauranosuchus delfsi (Mook, 1967; Clark,

1986, 1994; AMNH 570)Goniopholis (Mook, 1942; Clark, 1986, 1994;

Salisbury et al., 1999; AMNH 5782)Pholidosaurus decipiens (Owen, 1878; Clark,

1986, 1994)Dyrosauridae (Buffetaut, 1978; Clark, 1986,

1994; CNRST-SUNY 190)Sokotosuchus ianwilsoni (Halstead 1975; Buffe-

taut, 1979; Clark, 1986, 1994)Pelagosaurus typus (EudesDeslongchamps, 1863;

BSP 1890.I.5)Teleosauridae (Buffetaut, 1982; Clark 1986, 1994;

AMNH 5138, BSP 1945.XV.1, GPIT Auer-1909-f.22, MB 1921.12)

Metriorhynchidae (Gasparini and Diaz, 1977;AMNH 997, BSP AS.I.504, MACN-N 95,SMNS 10116)

Hylaeochampsa vectiana (Clark and Norell, 1992;Ortega et al., 2000)

Bernissartia fagessi (Buscalioni and Sanz, 1990;Norell and Clark, 1990)

Borealosuchus formidabilis (Erickson, 1976; Bro-chu, 1997b)

Gavialis gangeticus (Clark, 1994; Brochu, 1997a)Crocodylus niloticus (Clark, 1994; Brochu,

1997a)Alligator mississippiensis (Clark, 1994; Brochu,

1997a)


APPENDIX 4

ANATOMICAL ABBREVIATIONS

alr anterolateral ridge of dorsal osteodermamr anteromedial ridge of dorsal osteodermang angularapal anterior palpebralapj ascending process of jugalar angular ridgecc crista craniiden dentarydo dorsal osteodermdok dorsal osteoderm keeldpo descending process of posterior

palpebraldpp descending process of postorbitaldr diapophyseal ridgefps fronto-parietal suturefr frontalho humeral osteodermshu humerushy hypapophysisitf infratemporal fenestraj jugaljr jugal infratemporal ridgelok lateral osteoderm keel

mas ventral surface of medial articular shelfns neural spinepa parapophysispar parietalpho proximal humeral osteodermpo postorbitalppal posterior palpebralppr parapophyseal ridgepr parietal posterolateral ridgeprp posterolateral process of retroarticularpsq posterolateral process of squamosalpuo proximal ulnar osteodermpz postzygapophysisqj quadratojugalra retroarticular processsang surangularsar surangular ridgesq squamosalsqr ridges of posterolateral process of

squamosalsto remnant of supratemporal openingul ulnauo ulnar osteodermvco ventral closure of olfactory tract

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A New Gobiosuchid Crocodyliform Taxon from the Cretaceous ...

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