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The occurrence of Psittacosaurus xinjiangensis Sereno and Chow, 1988 in the Urho area, Junggar Basin, Xinjiang, People’s Republic of China Donald B. Brinkman, David A. Eberth, M.J. Ryan, and Pei-ji Chen Abstract: A partial specimen of Psittacosaurus xinjiangensis from the Urho locality in the Western Junggar basin, China, extends the known geographical range of P. xinjiangensis and documents the adult morphology in this species. Variation in the number of denticles on the dentary tooth crowns is documented, possibly representing a decrease in the number of denticles during growth, although a high denticle count remains a diagnostic feature of the species. Résumé : Un spécimen partiel de Psittacosaurus xinjiangensis provenant de la région d’Urbo dans le bassin Junggar ouest agrandit l’étendue géographique connue de P. xinjiangensis et renseigne sur la morphologie de l’adulte de cette espèce. La variation du nombre de denticules sur les couronnes des dents du dentaire est documentée, représentant possiblement une diminution du nombre de denticules durant la croissance, bien que le grand nombre de denticules demeure l’une des caractéristiques de diagnostic de l’espèce. [Traduit par la Rédaction] 1786 Brinkman et al. Introduction Psittacosaurus is a small basal member of the Ceratopsia. Seven valid species (P. mongoliensis Osborn 1924, P. sinensis, Young 1958, P. meileyingensis Sereno et al. 1988, P. xinjiangensis Sereno and Chao 1988, P. neimogoliensis Russell and Zhao 1996, P. ordosensis Russell and Zhao 1996, and P. mazongshanensis Xu 1997) are known from the Early Cretaceous of Central Asia and Japan (Manabe and Hasegawa 1991). An additional species, P. sattayaraki was described by Buffetaut and Suteethorn (1992) based on a single dentary from Thailand, but its validity in the absence of more material has been questioned (Russell and Zhao 1996). Psittacosaurus was first collected in Xinjiang during expeditions to the Western Junggar Basin by the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in 1964 (Dong 1973a, 1973b). The IVPP collected Early Creta- ceous vertebrates in two areas, Urho and Delanshan (Fig. 1). In both areas, the assemblage is dominated by the pterosaur Djungaripterus, and the assemblage was referred to as the Djungaripterus fauna. The two localities differ in that dino- saurs are more abundant at the Delanshan locality, and the primitive ceratopsian Psittacosaurus, described by Sereno and Chao (1988) as Psittacosaurus xinjiangensis, was recovered at Delanshan but not at Urho. Although fragments of various specimens were collected documenting a size range, the most complete skeleton, and the type specimen of P. xinjiangensis was a juvenile. In this paper, a psittacosaur specimen collected in the Urho area during sedimentological studies of the Tugulu Group in this area is described. The specimen is of an adult individual. Although incomplete, it includes diagnostic elements that allow it to be identified as Psittacosaurus xinjiangensis. This specimen provides the first documentation of the adult morphology in this species and provides further evidence on the variation in this species. The presence of P . xinjiangensis in the Urho area reinforces the faunal similarity of the Urho and Delanshan localities. Institutional abbreviations AMNH, American Museum of Natural History, New York, N.Y.; IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, Beijing, China; UGM, Urumqi Geological Museum, Urumqi, Xinjiong, China. Systematic Paleontology Class Reptilia Order Ornithischia Suborder Certaopsia Marsh, 1890 Family Psittacosauridae Genus Psittacosaurus Osborn 1923 Psittacosaurus xinjiangensis Sereno and Chao 1988 Can. J. Earth Sci. 38: 1781–1786 (2001) © 2001 NRC Canada 1781 DOI: 10.1139/cjes-38-12-1781 Received February 1, 2001. Accepted June 27, 2001. Published on the NRC Research Press Web site at http://cjes.nrc.ca on November 21, 2001. Paper handled by Associate Editor H.-D. Sues. D.B. Brinkman, 1 D.A. Eberth, and M.J. Ryan. Royal Tyrrell Museum of Palaeontology, Box 7500 Drumheller, AB T0J 0Y0, Canada. C. Pei-ji. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 21008, China. 1 Corresponding author (e-mail: [email protected]).

Brinkman et al, 2001

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Donald B. Brinkman, David A. Eberth, M.J. Ryan, and Pei-ji Chen Institutional abbreviations AMNH, American Museum of Natural History, New York, N.Y.; IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, Beijing, China; UGM, Urumqi Geological Museum, Urumqi, Xinjiong, China. Introduction 1 Corresponding author (e-mail: [email protected]). 1781 [Traduit par la Rédaction] 1786 Paper handled by Associate Editor H.-D. Sues. Brinkman et al.

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The occurrence of Psittacosaurus xinjiangensisSereno and Chow, 1988 in the Urho area, JunggarBasin, Xinjiang, People’s Republic of China

Donald B. Brinkman, David A. Eberth, M.J. Ryan, and Pei-ji Chen

Abstract: A partial specimen ofPsittacosaurus xinjiangensisfrom the Urho locality in the Western Junggar basin,China, extends the known geographical range ofP. xinjiangensisand documents the adult morphology in this species.Variation in the number of denticles on the dentary tooth crowns is documented, possibly representing a decrease inthe number of denticles during growth, although a high denticle count remains a diagnostic feature of the species.

Résumé: Un spécimen partiel dePsittacosaurus xinjiangensisprovenant de la région d’Urbo dans le bassin Junggarouest agrandit l’étendue géographique connue deP. xinjiangensiset renseigne sur la morphologie de l’adulte de cetteespèce. La variation du nombre de denticules sur les couronnes des dents du dentaire est documentée, représentantpossiblement une diminution du nombre de denticules durant la croissance, bien que le grand nombre de denticules demeurel’une des caractéristiques de diagnostic de l’espèce.

[Traduit par la Rédaction] 1786

Brinkman et al.Introduction

Psittacosaurusis a small basal member of the Ceratopsia.Seven valid species (P. mongoliensis Osborn 1924,P. sinensis, Young 1958,P. meileyingensisSereno et al. 1988,P. xinjiangensisSereno and Chao 1988,P. neimogoliensisRussell and Zhao 1996,P. ordosensisRussell and Zhao1996, andP. mazongshanensisXu 1997) are known from theEarly Cretaceous of Central Asia and Japan (Manabe andHasegawa 1991). An additional species,P. sattayarakiwasdescribed by Buffetaut and Suteethorn (1992) based on asingle dentary from Thailand, but its validity in the absenceof more material has been questioned (Russell and Zhao1996).

Psittacosauruswas first collected in Xinjiang duringexpeditions to the Western Junggar Basin by the Institute ofVertebrate Paleontology and Paleoanthropology (IVPP) in1964 (Dong 1973a, 1973b). The IVPP collected Early Creta-ceous vertebrates in two areas, Urho and Delanshan (Fig. 1).In both areas, the assemblage is dominated by the pterosaurDjungaripterus, and the assemblage was referred to as theDjungaripterusfauna. The two localities differ in that dino-saurs are more abundant at the Delanshan locality, and theprimitive ceratopsianPsittacosaurus, described by Serenoand Chao (1988) asPsittacosaurus xinjiangensis, was recoveredat Delanshan but not at Urho. Although fragments of variousspecimens were collected documenting a size range, the

most complete skeleton, and the type specimen ofP. xinjiangensiswas a juvenile.

In this paper, a psittacosaur specimen collected in theUrho area during sedimentological studies of the TuguluGroup in this area is described. The specimen is of an adultindividual. Although incomplete, it includes diagnosticelements that allow it to be identified asPsittacosaurusxinjiangensis. This specimen provides the first documentationof the adult morphology in this species and provides furtherevidence on the variation in this species. The presence ofP.xinjiangensisin the Urho area reinforces the faunal similarityof the Urho and Delanshan localities.

Institutional abbreviationsAMNH, American Museum of Natural History, New

York, N.Y.; IVPP, Institute of Vertebrate Paleontology andPaleoanthropology, Academia Sinica, Beijing, China; UGM,Urumqi Geological Museum, Urumqi, Xinjiong, China.

Systematic Paleontology

Class ReptiliaOrder OrnithischiaSuborder Certaopsia Marsh, 1890Family PsittacosauridaeGenus PsittacosaurusOsborn 1923Psittacosaurus xinjiangensisSereno and Chao 1988

Can. J. Earth Sci.38: 1781–1786 (2001) © 2001 NRC Canada

1781

DOI: 10.1139/cjes-38-12-1781

Received February 1, 2001. Accepted June 27, 2001. Published on the NRC Research Press Web site at http://cjes.nrc.ca onNovember 21, 2001.

Paper handled by Associate Editor H.-D. Sues.

D.B. Brinkman,1 D.A. Eberth, and M.J. Ryan. Royal Tyrrell Museum of Palaeontology, Box 7500 Drumheller, AB T0J 0Y0,Canada.C. Pei-ji. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 21008, China.

1Corresponding author (e-mail: [email protected]).

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Referred specimenUGM XG94Kh201. A partial skeleton, including skull

and jaw fragments, atlas, centrum, much of the presacralvertebral column and complete sacrum, partial rightforelimb, and complete right hind limb.

Locality and stratigraphyThe specimen was collected 10 km east-southeast of Urho

(Fig. 1) from the middle of the Lower Cretaceous TuguluGroup (Bureau of Geology and Mineral Resources ofXinjiang Uygur Autonomous Region 1985). Whereas theTugulu Group is recognized regionally across the Junggar,Tarim and Turpan basins, it is subdivided in different waysat different locations (e.g., Hendrix et al. 1992). The 1 : 200 000geological survey map of the Xinjiang Autonomous Region(Division 2 1978) recognizes four subgroups in the Tuguluof northwestern Xinjiang that are identified in ascendingstratigraphic order asa–d. The subgroups consist of discretefacies associations that indicate changes in depositional styleduring the Early Cretaceous in the internally drained, sea-sonally hot-and-dry Junggar Basin. Paleoenvironments in-ferred from the facies associations include distal braidplain(Tugulu a), braided fluvial and ephemeral floodplain(Tugulu b and d), and alluvial–lacustrine (Tuguluc). Thespecimen described here was collected from Tuguluc subgroup.

In the Urho area, the Tuguluc subgroup consists ofdecimetre-to-metre-scale interbedded sheets of red, massive-to-laminated mudrocks, grey shales, and very fine-grainedsandstones with intraformational mudstone pebbles anddesiccation-mudchip clasts. This facies association is inter-preted as the deposits of splays, sheet floods and slack waterin a low-gradient, seasonally arid setting that was dominatedby ephemeral ponds, extensive floodplains, and marshes(Eberth et al. 1995). The specimen was collected from asideritized, silty-to-very-fine-grained, massive, flat-basedsandstone sheet, 20–30 cm thick. This deposit can be reasonablyinterpreted as resulting from high rates of surface runoffduring either a splay or sheet-flood event.

Description and comparisonSpecimen UGM XG94Kh201 is a mature individual, similar

in size to the type specimen ofP. mongoliensis(AMNH6254; Osborn 1924, fig. 1). Additionally, the neural arches,where visible, appear to have fused to the centrum and havebeen broken off at their fused bases.

The skull is represented by a few isolated fragments,including a partial jugal preserving the base of the jugalhorn; articulated fragments of the occipital, quadrate, andsquamosal portions of the left maxilla; and the basioccipital–basisphenoid portion of the braincase. A portion of the leftjugal is preserved (Fig. 2A). As seen in all psittacosaurs, thelateral surface of the jugal is divided into two planes. Thejugal is thickened through the midline ridge, and a distincthorn would have projected from the ventral margin of thebone. As in the type specimen ofP. xinjiangensis, and incontrast to other species in the genus, the anterior surface ofthe horn is flattened. The jugal horn of specimen UGMXG94Kh201 differs from that of the type specimen in lack-ing the fine, radiating grooves described by Sereno and Chao(1988). We suspect that the striations in the type specimensare a feature similar to the long-grain bone texture thatSampson et al. (1997) described as feature of juvenileceratopsids that islost during growth. Thus this difference is aresult of differences in thestage of development of the twospecimens.

The posterolateral portion of the left squamosal (Fig. 2B)is preserved in articulation with a fragment of the occipitalportion of the parietal and the proximal surface of the leftquadrate. A portion of the posterior articulating surface forthe postorbital is preserved. All these fragments are of typicalPsittacosaurusshape.

The basioccipital–basisphenoid fragment (Figs. 2C, 2D)preserves the ventral portion of the foramen magnum andthe occipital condyle. Lateral to the condyle two foraminaare present. Following Xu (1997), these are identified asforamen for cranial nerves X–IX, and XI. This braincasefragment is not diagnostic forP. xinjiangensis.

Portions of both maxillae are preserved (Fig. 3A). The leftmaxilla appears to preserve the complete tooth row of eightteeth, but all their crowns are broken off. The right maxillapreserves parts of five teeth, tentatively identified as numbersone to five, with the best preserved teeth, numbers two andthree, exhibiting lateral surface features below their brokenapices. Also, a single, small, isolated maxillary tooth is present.As in the type specimenP. xinjiangensis(Sereno and Chao1988), the crown of each maxillary tooth is broad and thelateral surface is divided into three prominent lobes. Theanterior lobe is flat, with the two more posterior lobes beingconvex anteroposteriorly. The anterior-most lobe is thebroadest, with the middle and posterior lobes becomingprogressively smaller. The posterior lobe has at least twosmall apical tips preserved along the lateral margins of thecutting surface. These tips do not wrap around onto themedial surface to the same degree as in the type ofP.xinjiangensis. The type specimen ofP. xinjiangensishas asmany as 14 denticles on the maxillary crowns whereas otherpsittacosaurs bear 8–11 (Sereno and Chao 1988). This isolatedtooth of UGM XG94Kh201 has nine denticles preserved,and up to two more may have been present on the brokenportion of the posterior lobe. However, its small size relative

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Fig. 1. Locality map of the Junggar Basin of western China showingthe areas of exposure of the Lower Cretaceous sediments. Basedon Dong (1992, Fig. 91). Spelling of place-names follows Dong(1992).

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to the other preserved teeth suggests that it is from theextreme end row position, so the small denticle number mayreflect variation along the tooth row. Whatever the case, this

specimen suggests that the denticle count on maxillary teethof P. xinjiangensisis variable, either between individuals oracross the tooth row, and brings the range of variationexhibited inP. xinjiangensiswithin the range seen in otherpsittacosaur species. The presence of the small posteriordenticles progressing onto the medial surface remains diagnosticfor this species.

The lower jaw is represented by a significant portion ofthe dentary (Fig. 3B) and postdentary bones of the leftramus. The dentary is preserved in two parts with only asmall portion, including alveoli four, missing. As in the typespecimen, the dentary has a sharp ventral edge and lacks anydevelopment of a ventral flange. In inner view, the dentary isslightly concave. This surface is separated from thepostdentary region by a distinct ridge. The postdentary has arounded ventral edge preserving a portion of the Meckalianfossa.

Eight tooth positions are present on the dentary, with sixof these containing teeth. Two of the teeth, the third and seventhwere recently erupted prior to death. Tooth three shows wearonly at several of its extreme apical tips, while tooth sevenshows minor wear across the crown and across its lateralsurface. As in the only known dentary tooth in the typematerial (IVPP V7704; Figs. 5C, 5D; Sereno and Chao1988), and the crowns of adult psittacosaur species, thecrown is circular in lateral view and its medial surface issubdivided into three lobes. The median lobe is larger thaneither the anterior or posterior lobes, being inflated at thebase of the crown and tapering to a blunt apex, which inunworn teeth, projects beyond the circular crown. In the typespecimen, the denticle row forms a semicircle around themargin of the crown, extending well down both sides. Intooth number seven of specimen UGM XG94Kh201, themost completely preserved tooth in the series, the denticlesare more nearly transversely arranged across the dorsal edgeof the tooth. Tooth three is intermediate in its condition inthat on the anterior end of the tooth, the denticles follow theanterior edge of the tooth and thus form part of a semicircle,while the posterior denticles are restricted to the dorsal edgeof the crown. The lateral surface of tooth seven has awell-defined medial groove opposite the apical denticle.Poorly defined secondary ridges separated by shallowdepressions are present on either side of the median groove.

The type specimen ofPsittacosaurus xinjiangensishas tensecondary denticles symmetrically distributed on either sideof the median ridge, significantly more than is present inother species in the genus, except forP. mazongshanensis(dentary crowns bear a total of 9–15 denticles in other species,Russell and Zhao 1996). The high number of denticles wassuggested to be a derived feature linkingP. xinjiangensisandP. mazongshanensis. However, specimen UGM XG94Kh201shows that the number of denticles on the edge of the dentaryteeth varies withinP. xinjiangensis. Tooth seven, the bestpreserved tooth in the series in specimen UGMXG94Kh201, has nine denticles in front of the apicaldenticle and eight behind, giving a total of eighteen denticlesalong the edge of the tooth. Tooth three has thirteendenticles along the edge of the tooth with six on either sideof the apical denticle. Thus, the number of denticles on thedentary teeth inP. xinjiangensisis variable along the toothrow, ranging from that known for other psittacosaur species,

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Fig. 2. Psittacosaurus xinjiangensis. Cranial elements (specimenUGM XG94Kh201). (A) lateral view of left jugal, (B) dorsal viewof left squamosal, (C) occipital and (D) ventral view of basicranium.bo, basioccipital; bs, basispenoid; cn, cranial nerve fenestra ; fm,foramen magnum; jam, jugal anterior margin; mitf, margin ofinfratemporal fenestra; oc, occipital condyle; po, sulcus forpostorbital; q, quadrate. Scale bar = 1 cm.

Fig. 3. Psittacosaurus xinjiangensis. Cranial elements (UGMXG94Kh201). (A) medial view of right maxilla and (B) medialview of left dentary. cor, broken base of coronoid process.Scale bar = 1 cm.

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to an increased number diagnostic forP. xinjiangensis, withthe highest counts present in the posterior region of the jaw.

The vertebral column is preserved in two major sections(Figs. 4, 5). The vertebral column ofPsittacosaurustypically

includes 21 presacrals, 6 sacrals, and-45 caudals, althoughP. neimongoliensisandP. mongoliensisvary from this in thepresence of an extra presacral (Sereno 1990). Using the typicalcondition as a basis for comparison, the vertebrae preservedin specimen UGM XG94Kh201 are the atlas, presacrals 10–21,the six fused sacrals of the sacrum, and the first caudalvertabra.

Ossified epaxial tendons preserved on UGM XG94Kh201extend from the most cranially preserved presacral vertebra,across the sacrum, and onto the first and only preserved caudalvertebra. In the position of the epaxial tendons,P. xinjiangensisis similar toP. mongoliensis, where tendonsrun from the 10th presacral to the 15th caudal, and differentfrom P. sinensisand possiblyP. meileyingensis, where notendons span the sacral region.

Both ilia are present, although incomplete. Between them,only the distal tip of the posterior process is not represented.The ilium of specimen UGM XG94Kh201 is comparable tothat of the type specimen ofP. xinjiangensis in that thepostacetabular process is long relative to its height. In UGMXG94Kh201, the base of the process is preserved on the left

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Fig. 4. Psittacosaurus xinjiangensis. Ventral view of vertebral series (UGM XGP4Kh201). c, caudal vertebra; ps, presacral vertebra; r, rib; s,sacral vertebra; sr, sacral rib. Scale bar = 2 cm.

Fig. 5. Psittacosaurus xinjiangensis. Partial right forelimb (UGMXGP4Kh201). h, humerus; ps, presacral vertebra; r, rib fragment;ra, radius; ul, ulna. Scale bar = 2 cm.

Fig. 6. Psittacosaurus xinjiangensis. Left ilium (UGM XG94Kh201).(A) lateral and (B) medial views. s, articular surface for sacralvertebra. Scale bar = 2 cm.

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ilium, and the distal end is preserved on the right. Fromthese two portions, the length of the postacetabular processis a minimum of 6 cm. The height midway along the processis 2 cm. In this feature,P. xinjiangensisdiffers from otherspecies ofPsittacosaurus, which have a relatively muchdeeper postacetabular process. The anterior process, incom-pletely preserved in the type specimen, is a long narrowblade. The preserved portion of the illustrated left ilium(Fig. 6) has a smoothly curved lateral surface without a ventralflange, such as is present inP. mongoliensis.

The appendicular region is represented by a portion of theforelimb (Fig. 5) and a complete hind limb (Fig. 7). Theforelimb includes the distal humerus and the proximal radiusand ulna. As is typical for psittacosaurs, and to a largeextend for complete specimens ofProtoceratops andrewsi,the knee and ankle appear to be hyperflexed so that thefemur lies almost parallel to the tibia and fibula, and the footis plantigrade.

Discussion

Psittacosaur species are distinguished primarily on theshape of the jugal horn, ornamentation of the dentition, andshape of the ilium. Specimen UGM XG94Kh201 is referredto P. xinjiangensisby the following features; the anteriorlyflattened jugal horn, increased number of dentary denticlesover other species, and the possession of an elongate iliacpostacetabular process. It differs from the type specimen inthat the dentary teeth have fewer denticles (maximum 18rather than 21) and that the number of denticles on the teethappears to be variable along the tooth row. This difference is

assumed to represent variation within the species. Since thesmaller individual has a higher denticle count, it may be thatthis represents a decrease in the number of denticles duringontogeny. However, inP. mongoliensis, the denticle countincreases from juveniles to adults (Sereno 1990). Additionalspecimens are needed to resolve whether the lower numberof denticles in UGM XG94Kh201 is truly a result ofontogenetic change or simply reflects variation within adultsof the species. The two specimens also differ in thatstriations on the jugal horn are absent. This may be a reflectionof the relative stage of development of individual specimens.As described by Sampson et al. (1997), in ceratopsids, thepresence of striations on the cranial bones is a juvenile featurethat is lost during growth. The presence of striations in thetype specimen, a juvenile individual, and their absence inUGM XG94Kh201, an adult, suggests that psittacosaurs mayshow a similar pattern of ontogenetic development.

Specimen UGM XG94Kh201 provides the first documen-tation of Psittacosaurus xinjiangensisat the Urho locality.Previously the only ornithischian identified from the Urholocality wasWuerhosaurus. The occurrence ofPsittacosaurusin this area is not surprising given the general similarity inthe assemblages of the Urho and Delanshan localities (Dong1973a, 1973b). The greater abundance of dinosaur remainsin the Delanshan locality has been interpreted as a result ofecological factors related to the environment of deposition ofthese areas. Dong (1992) interpreted the sediments in theUrho area as lacustrine, and suggested that the fossil assem-blages of the two areas differed because the Delanshan areapreserved a shoreline assemblage. However, examination ofthe sediments at the Urho area has revealed that they were

Fig. 7. Psittacosaurus xinjiangensis. Right hind limb (UGM XG94Kh201) folded in squatting position. (A) ventral and (B) dorsal viewsof the leg. (C) proximal view of tarsals. II, second digit; III, third digit; IV, forth digit; as, astragalus; ca, calcaneum; dist, distal tarsal;fi, fibula; fe, femur; medt, medial tarsal; mt, metatarsal; ti, tibia; ?p, ?right pubis; r, rib fragments. Scale bar = 2 cm.

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deposited in a semi-arid, fluvial–lacustrine setting characterizedby at least, seasonal subaerial exposure, similar to the modernenvironments in this area and other basins across northernChina (cf. Eberth 1993). Thus, the difference in faunalcomposition between Delanshan and Urho is more likely areflection of differences in other aspects of the terrestrialpaleoenvironments, climate, and (or) preservational processes.

One striking feature of UGM XG94Kh201, as preserved,is the posture of the hind limb. This posture is frequentlyencountered in bothPsittacosaurusand basal ceratopsidssuch asProtoceratops. Given the apparent hyperextension ofthe knee and ankle joints that this entails, it has beenassumed that this is an artificial position. However, thefrequency with which this position is encountered raises thepossibility that this is a normal resting posture, possiblyexaggerated by the compression of the elements resultingfrom the loss of the soft tissue. Jerzykiewicz et al. (l993)concluded that many of the articulatedProtoceratopsspecimensthat are oriented subhorizontally and belly down are theremains of animals that died in situ and were probablyburied by sandstorm events. Fastovsky et al. (1997) deter-mined that the articulatedProtoceratopsspecimens that theyencountered in the south-central Gobi Desert of Mongolia,in which the limbs were drawn up to their bodies, were theresult of animals dying on the lee side of prograding eoliandunes, presumably overwhelmed by sandstorms. Thecrouched position of UGM XG94Kh201, common amongstother psittacosaurs and articulated Asian neoceratopsians,can be interpreted as a natural position that would havereduced their body profiles during inclement weather andmight have been a natural position for other activities suchas feeding or nest incubation.

Acknowledgments

The specimen described here was discovered during a jointRoyal Tyrrell Museum of Paleontology – PaleontologicalInstitute of Nanjing expedition to the Junggar Basin, aimedat studying the stratigraphy and environments of the basin,and was supported by a grant from the National GeographicalSociety. Irene Hughes drew Figs. 2 through 7. ChadKerychuk of Digital Dream Machine (Edmonton, Alberta)assisted with figure formating. We would also like to thankPeter Makovicky and Dale Russell for reviewing the manuscript.

References

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Dong, Z.-m. 1973a. Cretaceous stratigraphy of Wuerho district,Dsungar Basin. Reports of Paleontological Expedition toSinkiang (II). Pterosaurian Fauna from Wuerlo, Sinjiang. Memoirsof the Institute of Vertebrate Paleontology and Paleoanthropology,11: 1–7.

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