An Early Ostrich Dinosaur and Implications for Ornithomimosaur Phylogeny

Home , Anserimimus, Shenzhousaurus

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3420, 19 pp., 12 ®gures, 1 table October 29, 2003

QIANG JI,1 MARK A. NORELL,2 PETER J. MAKOVICKY,3 KE-QIN GAO,4 SHU'AN JI,4 AND CHONGXI YUAN5

ABSTRACT A new ornithomimosaur from the Yixian Formation of Liaoning Province People's Republic of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen is interesting because it has several primitive characters for ornithomimosaurs such as teeth and a short ®rst metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we comment on the biogeographic history of this group.

INTRODUCTION and often preserving soft-part anatomy, these fossils can be frustrating because of a lack of Spectacular fossils from China's Liaoning three-dimensional preservation. Furthermore, Province have become commonplace in the theropod remains from Liaoning only in- last few years (Ji and Ji, 1996; Ji et al., 1999; clude the maniraptoran groups Dromaeosaur- Hou, 1997; Gao et al., 2000). However, most idae (Xu et al., 1999b, 2000), Oviraptorosau- of these are nearly two-dimensional fossils ria (Ji et al., 1998, Xu et al., 2002a), Troo- found in paper shales that represent ancient dontidae (Xu et al., 2002b), and Segnosaur- pond and lake deposits. Although beautiful idae (Xu et al., 1999a) and the more

1 Department of Earth Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, and Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037 China. e-mail: [email protected] 2 Division of Paleontology, American Museum of Natural History. e-mail: [email protected] 3 The Field Museum, 1400 S. Lake Shore Drive, Chicago IL, 60660. e-mail: pmakovicky@®eldmuseum.org 4 School of Earth and Space Sciences, Peking University, Beijing 100871, China. e-mail: [email protected]. edu.cn 5 China University of Geosciences, Beijing 100083, China.

Copyright ᭧ American Museum of Natural History 2003 ISSN 0003-0082 2 AMERICAN MUSEUM NOVITATES NO. 3420 primitive compsognathid Sinosauropteryx head above the torso. The distal hindlimbs, (Chen et al., 1998). Here we describe a new distal tail, and the forelimbs (except for part ornithomimid dinosaur, the ®rst from the of the right hand) and the pectoral girdle are Liaoning beds, and comment on its relation- missing. The head is crushed, exposing the ships to other ornithomimids. left side obliquely. Ornithomimid dinosaurs were the ®rst ETYMOLOGY: Shenzhou is the ancient name toothless nonavian dinosaurs to be described of China, orientalis refers to the east. (Marsh, 1890). Consequently, much has been TYPE LOCALITY: Sihetun fossil site, Bei- written concerning their relationships and piao, Western Liaoning, China (®g. 3). diet (Gauthier, 1986; Holtz, 1994; Sereno, GEOLOGICAL OCCURRENCE: The holotype 1997, Kobayashi et al., 1999; Norell et al., comes from the lowermost, ¯uvial part of the 2001b). Although toothed forms have been Early Cretaceous Yixian Formation. These recovered (PeÂrez-Moreno et al., 1994; Bars- rocks are older than 128 mybp and younger bold and Perle, 1984), these are either dif®- than 139 mybp (Swisher et al., 2002); older cult to place phylogenetically or are extreme- dates have been reported (Lo et al., 1999). ly fragmentary. DIAGNOSIS: an ornithomimosaur distin- Local farmers collected the specimen, and guishable from all others except Harpymimus some of the elements were clearly lost during in having teeth restricted to the anterior den- the excavation process. It is apparent that tary. Shenzhousaurus orientalis shows prim- both the tail and the forelimbs were present itive characters not found in advanced orni- in adjoining blocks (®g. 1). When the spec- thomimosaurs, like a straight ischium and a imen was collected it was cracked into two postacetabular process that is gently curved blocks, shattering many bones and leaving rather than truncated. Shenzhousaurus orien- parts of the skeleton in each block. During talis is distinguishable from Pelecanimimus the preparation process parts of the counter by the tooth distribution pattern and the block were glued to the main slab, and the primitive con®guration of the hand where sediment surrounding the bones was re- digit I is shorter than digits II and III. moved. In other cases individual elements were prepared completely free of the counter DESCRIPTION slab and af®xed to the main slab. This prep- SKULL aration process resulted in a single block with the specimen preserved in bas-relief The left side of the snout is well pre- (®g. 2). served, whereas the right side is crushed and displaced postmortem (®g. 4). The orbital INSTITUTIONAL ABBREVIATIONS and braincase regions are ¯attened and the AMNH American Museum of Natural History left frontal and parietal are ¯ipped under the IGM Institute of Geology Mongolia right. The left squamosal is isolated and lies NGMC National Geological Museum of China adjacent to the caudal end of the lower jaw. ROM Royal Ontario Museum The left mandible appears to be intact and well preserved. The premaxilla has a relatively short body, SYSTEMATIC PALEONTOLOGY and the premaxillary buccal margin is only THEROPODA MARSH, 1881 as long as the external naris. The internarial COELUROSAURIA VON HUENE, 1914 bar is dorsoventrally ¯at and is formed mainly by the premaxillae, with only a minor con- ORNITHOMIMOSAURIA BARSBOLD, 1976 tribution from the nasals. The posterodorsal ORNITHOMIMINAE SERENO, 1998 process of the premaxilla is elongate as in other ornithomimids, and it overlaps the na- Shenzhousaurus orientalis, new taxon somaxillary suture well posterior to the cau- TYPE SPECIMEN: NGMC (National Geolog- dal end of the naris. It is broadest at its base ical Museum of China) 97-4-002. but tapers caudally. Although incomplete dis- MATERIAL: A partial skeleton preserved on tally, it does not appear to have reached the a sandstone block in a death pose with its level of the antorbital fossa. The labial sur- 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 3

Fig. 1. NGMC 97-4-002 before preparation. 4 AMERICAN MUSEUM NOVITATES NO. 3420

Fig. 2. The holotype skeleton of Shenzhousaurus orientalis as preserved on the main block, with parts in counterblock reattached. Abbreviations: g, gastralia; ga, gastroliths; lf, left femur; li, left ilium; lis, left ischium; lp, left pubis; lu, ungual of left hand; pb, pubic boot; r-dI, right digit I; r-dII, right digit II; r-dIII, right digit III; rf, right femur; rp, right pubis. 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 5

larger antorbital and a smaller accessory fenestra. The rostral 40% of the maxilla lies anterior to the antorbital fenestra and has a ¯at lateral surface marked only by a few foramina, presumably for neurovascular trans- mission. The buccal margin is slightly sinuous in this region and rises gently toward the front. The buccal margin of the maxilla is very shallow beneath the antorbital fossa. A large maxillary palatal shelf is visible along the anterior two-thirds of the antorbital fossa. The fossa appears to be bordered by the nasal for a short stretch dorsal to the antorbital fenestra, although the maxilla is not complete in this region. Posterior to this the dorsal edge of the antorbital fenestra is bordered by the elongate anterior ramus of the lacrimal. The accessory fenestra perforates a de- pressed medial lamina of the maxilla that walls off the anterior third of the antorbital Fig. 3. The fossil locality. fossa medially. The posterior part of this lamina, which forms the interfenestral bar, bears dorsal and ventral embayments along face of the subnarial part of the premaxilla the posterior border, perhaps indicating some is marked by a few neurovascular foramina, type of interfenestral connection as in troo- the largest of which is located at the base of dontids (Norell et al., 2000; Makovicky et the internarial bar. al., 2003). The maxilla is very elongate and bears a The jugal is poorly preserved, and articu- large antorbital fossa that is perforated by a lar contacts with the maxilla and lacrimal

Fig. 4. Close-up of the left side of the skull of Shenzhousaurus orientalis. Abbreviations: ch, choana; fr, frontal; ld, left dentary; ll, left lacrimal; lmx, left maxilla; ln, left nasal; lpmx, left premaxilla; lsq, left squamosal; mxf, maxillary fenestra; plr, palatine recess; rn, right nasal. 6 AMERICAN MUSEUM NOVITATES NO. 3420 cannot be traced. The orbital portion of the tending anteriorly around the caudal end of jugal is very slender, and the anteroventral the supratemporal fenestra, a rostroventrally corner of the orbit appears to have had a directed quadrate process that adheres to the right-angled rather than a rounded shape. anterior edge of the quadrate shaft, and a Posteriorly, the jugal is obscured by other el- short lateral process. The intertemporal pro- ements. cess of the squamosal is longer than the me- The lacrimal bears an elongate anterior dial supratemporal process. The dorsal sur- process that borders the caudal half of the face of the squamosal between these two pro- antorbital fenestra dorsally. A short, pointed cesses is incised by a caudal extension of the posterior process is present on the lacrimal. supratemporal fenestra, bordered by a sharp It may have inserted into a notch on the dor- rim, as in Gallimimus (IGM 100/1133). The sal surface of the prefrontal as in Gallimi- quadrate process of the squamosal is trian- mus, but the prefrontal cannot be identi®ed. gular. The posterolateral process extends pos- Neither large fossae nor hornlike structures terior to the quadrate articulation, but its are present on the lacrimal. length cannot be determined because it is A short section of the right postorbital is overlapped by a disarticulated piece of the exposed in dorsal view, and it forms the an- braincase. The articulation with the quadrate terior part of the intertemporal bar. It is rel- is not exposed in lateral view in Shenzhou- atively massive compared to the postorbital saurus orientalis,asitisinGallimimus contribution to the intertemporal bar in other (IGM 100/1133) and Ornithomimus. ornithomimid taxa. The postorbital of Shen- Parts of the palate, including parts of both zhousaurus orientalis does not reveal the palatines and possibly the left pterygoid, are characteristic anterodorsal curvature seen in exposed. The palatine bears two anteriorly maniraptorans. elongate processes that almost enclose the in- The right frontal is exposed in dorsal view ternal choana. The medial, interchoanal pro- (®g. 5). A coronally directed crack extending cess is longer than the lateral one, in contrast through the frontal just anterior to the artic- to Allosaurus (Madsen, 1976), but similar to ulation of the postorbital may be the result Sinraptor (Currie and Zhao, 1993) and Dei- of dorsoventral crushing of a strongly ¯exed nonychus (Witmer, 1997), and it extends at part of the frontal. The frontals of other or- least as far rostrally as the interfenestral bar. nithomimid taxa are domed near the posterior part of the orbit, forming a ¯exure be- The interchoanal process of the left side rises tween the ¯at parts of the frontal and parie- dorsomedially to meet its counterpart on the tals. Anterior to the extensive orbital rim, the right side and form the interchoanal bar, pos- lateral edge of the frontal is sinuous and the sibly with participation of the pterygoids. medially in¯ected portion may mark a de- The interchoanal bar is unlike the large, lo- pression for the reception of a prefrontal. bate structure of Allosaurus (Madsen, 1976), The parietals appear paired and unfused. but is more slender and curves anteriorly The dorsal surface of the parietal is ¯at and from the posterior end of the choana as in lacks a sagittal crest. A laterally concave Velociraptor (Barsbold and OsmoÂlska, ¯exure marks the medial edge of the supra- 1999). The dorsal surface of the palatine temporal fenestra and separates the dorsal bears a deep fossa, the palatine recess (Wit- surface of the parietal from the lateral surface mer, 1995), near the base of the maxillary that forms parts of the adductor chamber. The process just rostral to the level of the lacrimal frontoparietal suture is sinuous in dorsal (®g. 5). The palatine recess in Shenzhousau- view, as in Gallimimus (OsmoÂlska et al., rus orientalis is in a similar position to pal- 1972). atine recesses observed in dromaeosaurs The left squamosal is disarticulated and such as Deinonychus (Witmer, 1995: ®g. 32) lies adjacent to the caudal end of the left and Velociraptor (IGM 100/982). The recess mandible. It is exposed in lateral view, and invades the palatine body mediodorsally in the proximal end of the quadrate is preserved Shenzhousaurus orientalis rather than poster- in articulation with the squamosal. The squa- odorsally as in the two dromaeosaurid taxa. mosal is tetraradiate, with two processes ex- Part of the pterygoid process of the palatine 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 7

Fig. 5. Closeup of braincase. Abbreviations: dv, dorsal vertebra; f, frontal; lp, left prootic, ls?, left laterosphenoid, lsa, left surangular, lsq, left squamosal; r, rib. is exposed within the orbit, posterior to the ectopterygoid to this may represent a part of lacrimal. the pterygoid. The hooked jugal process is the only vis- A large, crushed bone that overlaps the ible part of the ectopterygoid and is exposed posterior part of the mandible may be a la- within the orbit slightly posterior to the pter- terosphenoid. We interpret a large broken el- ygoid process of the palatine. A narrow sliv- ement posterior to the right parietal as the left er of bone dorsal to the jugal process of the prootic with its anterior surface (laterosphen- 8 AMERICAN MUSEUM NOVITATES NO. 3420

Fig. 6. The dentition of Shenzhousaurus orientalis as preserved in the left dentary. oid articulation) facing upward (®g. 5). A splintlike process overlapping the dentary. well-delimited depression on the lateral sur- Fragments of the angular are exposed along face appears to be the dorsal tympanic recess. the ventral border of the external mandibular Medial to it, the posterior border of the ¯oc- fenestra. The glenoid and retroarticular pro- cular recess is visible. Part of the border of cess are exposed. A ¯attened area just rostral a large foramen, which is surrounded by a to the glenoid may correspond to the dorsal wide fossa on the lateral surface of the brain- trough or sulcus seen on the surangular of case, is visible anteroventral to the ¯occular many theropods, including Velociraptor, Ty- recess and is here interpreted as the exit for rannosaurus, and Ornitholestes. As in other the trigeminal nerve. ornithomimids, an everted tab forms the an- The complete left mandible is preserved, terolateral margin of the glenoid. In these but much of the postdentary region is cov- taxa, such as Gallimimus, this tab articulates ered by the unidenti®able braincase element. with an elongate, curved extension of the lat- The dentary is elongate but shallow and eral quadrate condyle. The retroarticular pro- spans about two-thirds the length of the jaw. cess is crushed, but it appears to be expanded The dentary is deepest below the middle of medially. the antorbital fenestra. It tapers gently rostral to this point, up to a point just posterior to TEETH the toothrow, where it de¯ects rostroventral- Six minute tooth crowns and a broken root ly. The buccal margin is de¯ected anteroven- are preserved at the de¯ected anterior tip of trally at the symphysis, as in other ornithom- the left dentary. Gaps between the preserved imosaurs except Pelecanimimus (PeÂrez-Mo- teeth suggest the presence of one or two ad- reno et al., 1994). The lateral surface of the ditional tooth positions. The teeth are conical dentary is pocked by three roughly linear and project slightly anteriorly. They do not rows of neurovascular foramina (®g. 6). have a constriction between the root and These extend posteriorly to the end of the crown. A thin layer of enamel is preserved abbreviated toothrow. Farther caudally, a on the teeth. There is no trace of either ca- shallow groove follows the dorsal margin of rinae or serrations. the dentary until it reaches the rostrodorsal AXIAL SKELETON process of the surangular. As in other ornithomimosaurs, the external CERVICAL VERTEBRAE mandibular fenestra is reduced. It is bordered No cervical vertebrae can be identi®ed on dorsally by the surangular that has a long, the specimen. 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 9

thomimus (Makovicky, 1995), Gallimimus (OsmoÂlska et al., 1972), Struthiomimus, and Archaeornithomimus (Makovicky, 1995). The ilium appears to be slightly displaced from the sacrum, thus exposing the transverse processes of the last sacral in lateral view. As in other ornithomimosaurs, the transverse processes of this element ¯are widely distally where they meet the medial border of the brevis fossa, and they may have contributed to the insertion area of the cau- difemoralis brevis musculature. The neural Fig. 7. Dorsal vertebrae of Shenzhousaurus spine of the last sacral appears to have been orientalis. freestanding, but it cannot be determined whether the neural spines of the remaining sacrals formed a lamina as in some other or- DORSAL VERTEBRAE nithomimosaurian specimens. An articulated series of the last eight dorsal vertebrae are preserved in articulation CAUDAL VERTEBRAE with the sacrum. The centra are elongate and A section of the tail comprising 15 artic- spool-shaped and are devoid of pneumatic ulated caudal vertebrae is preserved, curving foramina (®g. 7). The anteriormost centrum, posterodorsally from the sacrum (®g. 8). All which is broken anteriorly, bears a faint keel the preserved caudals possess transverse pro- ventrally. Neural arches bear large pneumatic cesses or traces thereof, indicating that the infraprezygapophyseal, infradiapophyseal, transition point lies distal to the preserved and infrapostzygapophyseal fossae below the section of the tail. Centrum length increases transverse processes. The infraprezygapo- distally in the preserved section, whereas physeal fossae are especially large and ap- centrum height decreases distally. pear to extend into the prezygapophyses. The The transverse processes are distally ex- neural spines are long, tall anteroposteriorly panded and backswept. Their distal ends are expanded distally. The neurocentral sutures rounded. In the second and third caudal ver- are fused but not obliterated. In no case is a tebrae, a thin lamina extends anteriorly from neural arch separated from its corresponding the transverse process on to the lateral face centrum. of the prezygapophysis, where it forms a dis- Parts of 10 dorsal ribs are preserved on the tinct ridge bounding a shallow fossa. This block, but none is complete. Two left ribs, connection between the transverse process which probably articulated with the fourth and prezygapophysis is also present in Or- and ®fth dorsals in the preserved series, have nithomimus. The neural spines of the ®rst 12 anteroposteriorly ¯ared shafts as in other or- vertebrae are obscured by transverse pro- nithomimids (Barsbold and OsmoÂlska, cesses. Those of the remaining three caudals 1990). are parallelogram-shaped and lean posteriorly, extending beyond the caudal end of SACRAL VERTEBRAE their respective centra. Parts of ®ve sacral vertebrae are exposed CHEVRONS but are partly obscured by the pelvic elements and the left femur. The centra appear The ®rst chevron is situated between the to be fused, but the sutural lines are still ev- ®rst and second caudals. It is rod-shaped, but ident. A constricted pit is visible on the ex- its length is indeterminate, as the second posed lateral surface of both the third and chevron covers it distally. The second to fourth sacrals. Such noninvasive depressions ®fths chevron are very elongate, slender, and are also present on the sacral vertebrae of rod-shaped with a slight posterior curvature other ornithomimid taxa, including Orni- that becomes more pronounced in more dis- 10 AMERICAN MUSEUM NOVITATES NO. 3420

Fig. 8. Anterior caudal vertebrae of Shenzhousaurus orientalis. tal elements. Posterior to this, the chevrons may have only comprised this medial ele- become progressively wider, mediolaterally ment compressed, shorter, and more hooked. The last two chevrons are strongly hooked and APPENDICULAR SKELETON end in a point distally. PELVIS

GASTRALIA The pelvis is present in semiarticulation although some elements were shattered when Parts of eight gastral arches from the right the slab was split. The ilium is about equal side are preserved, but only one preserves in length to the pubis, and the ischium is only both the complete medial and lateral seg- slightly shorter (see table 1). ments (®g. 9). The medial segment has an Most of the exposed dorsal surface of the expanded and dorsoventrally compressed ilium is shattered, as it lay on the contact midline end. It tapers distally and is over- between the slab and counterslab (®g. 10). lapped anteriorly by the lateral element. The Nevertheless, it can be determined that the two elements are approximately equal in anterior and posterior blades are roughly length, unlike those of higher ornithomimids, equivalent in length and that the iliac blade in which the medial elements are longer. The was dorsoventrally low. The ilia covered six dorsal ends of the rodlike lateral elements are vertebrae, less than in Gallimimus and Or- slightly expanded and curve dorsally. The nithomimus (Barsbold and OsmoÂlska, 1990). last gastral element is three times wider than Apparently the ilia met at the midline as in the preceding segments. The last gastral arch other ornithomimids (Makovicky et al., in 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 11

Fig. 9. Gastroliths of Shenzhousaurus orientalis. ga, gastroliths; ldIIIu, left digit 3 ungual; lf, left femur; li, left ilium; rdI, right digit 3, rdII; right digit 2; rdIII, right digit 3. press; Barsbold and OsmoÂlska, 1990). Both brevis fossa is straight (Barsbold and Os- anterior and posterior blades also are round- moÂlska 1990). The preacetabular apron is ed similar to the oviraptorosaur Khaan slightly concave and is separated from the mckennai (personal obs.). This is unlike the main body of the ilium by a sharp ridge that condition in other ornithomimids where the continues anteriorly to form the lateral bor- ilium is dolichoiliac and the posterior blade der of the deep cupedicus fossa. The acetab- is truncated rather than tapering to a point ulum is marked by a large supra-acetabular (Barsbold and OsmoÂlska 1990). Although the crest that overhangs the acetabulum. As is anterior blade is hooked as in other orni- typical of ornithomimosaurs, the supracetab- thomimids, the hook is small as in Khaan ular crest formed a hood or cap over the en- mckennai (personal obs.), Ornitholestes her- tire proximal femur. The ischiac peduncle is manni (Osborn, 1903), and Velociraptor not wide, but is formed as a ventral conical mongoliensis (Norell and Makovicky, 1997, process, as in other ornithomimids and tyran- 1999). Posterior to the acetabulum the lateral nosaurs, which inserts into a slot in the is- border of the brevis fossa is concave ven- chium. A large antitrochanter is present. The trally, giving it a slightly hooked appearance. postacetabular apron is large and like the This is unlike the condition in other orni- preacetabular apron is separated from the il- thomimids where the lateral margin of the iac blade by a large ridge that continues pos- 12 AMERICAN MUSEUM NOVITATES NO. 3420

TABLE 1 Measurements of Holotype of Shenzhousaurus orientalis (all measurements in millimeters)

teriorly to de®ne the lateral edge of the brev- large hook-shaped obturator process. It is is fossa. The brevis fossa is large and deep possible that this process may have com- and expands posteriorly as a deep trough to pletely enclosed a foramen; however, break- the posterior limit of the ilium. age in this area prevents con®rmation. Dis- The left ischium is preserved in near ar- tally the ischium tapers and then expands on ticulation with the ilium and can be observed its distal end into a small triangular boot that in lateral view. The iliac process is long and projects anteriorly. is angled posterodorsally from the shaft. On The left pubis and part of the right are ex- its posteroproximal lateral surface is a large posed laterally and are in near articulation triangular scar as in other ornithomimosaurs with the ilia and ischia. The overlying femur and tyrannosaurs (Buffetaut et al., 1996). The obscures most of its proximal features. How- surface of the acetabulum that lies in be- ever, the articulation with the ilium indicates tween the iliac and pubic processes is smooth that it was propubic. Near the iliac contact and crescent-shaped. The pubic process is the pubis is ¯at, becoming thin and rodlike short, relatively shorter than in other orni- distally. It is slightly anteriorly convex, and thomimids. In fact, the pubic contact lies laterally it is marked by a small sinuous lon- along the same axis as the shaft of the ischi- gitudinal ridge or crest which extends nearly um. Just ventral to the pubic contact lies a half the length of the shaft. This crest divides 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 13

Fig. 10. Pelvis of Shenzhousaurus orientalis. Abbreviations: ct, ectocondylar tuber; ft, fourth trochanter; gp, gastrocnemius process; gt, greater trochanter; lc, lateral crest; lf, left femur; lp, left pubis; li, left ilium; lis, left ischium; lt, lesser trochanter; mc, medial crest; o, obturator foramen; pb, pubic boot; rf, right femur, rp, right pubis; sac, sacrum. 14 AMERICAN MUSEUM NOVITATES NO. 3420

Fig. 11. Manus of Shenzhousaurus orientalis. ga, gastroliths; ldIIIu, left digit 3 ungual; rmcII, right metacarpal 2; rmcIII, right metacarpal 3; rpII-1, right digit 2 ®rst phalanx; rpII-2, right digit 2 second phalanx; rpIII-1, right digit 3 ®rst phalanx; rpIII-2, right digit 3 second phalanx; rpIII-3, right digit 3 third phalanx, rdIu, right digit 1 ungual; rdIIu, right digit 2 ungual; rdIIIu, right digit 3 ungual.

the pubis into anterior, and posterior-facing FORELIMB surfaces. Medially the pubic moietes meet to form the pubic apron, which is extensive, Only parts of the right hand, including all forming nearly two-thirds the length of the of digits II and III, and a single ungual of pubis. The pubic apron is posteriorly concave the left hand are preserved (®g. 11). The pre- and is formed from crests that emanate from served elements of the right hand are in ar- the anterior of the pubic shafts. Distally the ticulation, but the hand is situated at the edge pubes form a large pubic boot. At the ter- of the block, and the missing parts were ob- minus of the pubes the pubic boot appears to viously lost during collection when the block be transversally expanded. This boot is mod- was trimmed. The ungual and a partial im- erately expanded anteriorly, where it forms a pression of the penultimate phalanx are the pronounced point. Posteriorly the pubic boot only preserved parts of digit I. The ungual is is much more extensive. Ventrally the pubic slightly curved, not trenchant, and has a boot is deeply convex, as opposed to the con- small ¯exor tubercle situated distal to the dition in Gallimimus, where the ventral edge proximal articulation. A deep groove extends of the boot is nearly straight. along the medial surface of the ungual, to the 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 15 distal end of the ungual. The preserved un- imal articulation. The apparently ginglymous gual of digit I of the left manus shows a sim- distal articulation describes an arc of approx- ilar groove on the lateral surface, and these imately 180Њ and has a small, elliptical col- two grooves are parallel along the ungual, lateral ligament pit. The ungual of digit II is unlike the offset grooves on the unguals of similar to that of digit I, except that is slight- dromaeosaurs. As preserved, the ungual of ly longer. digit I does not reach the level of the prox- Metacarpal III is almost complete. It ap- imal end of the unguals of digits II and III. pears to be almost as thick as the preserved Because the hand is articulated, the pre- part of metacarpal II, as in Harpymimus served position of ungual I-2 re¯ects the ac- (Barsbold and OsmoÂlska, 1990). The proxi- tual proportions of the digits in life and in- mal end is triangular in proximal view, with dicates that digit I is proportionately shorter a slightly concave area where it was apressed than digits II or III, which is the primitive against the shaft of metacarpal II. The shaft condition for Tetanurae (Gauthier, 1986; Ser- of metacarpal III appears to curve slightly eno, 1997). Among ornithomimosaurs, the laterally. The distal articulation divides into condition in Shenzhousaurus appears most two tubera ventrally. like that of Harpymimus (Barsbold and Perle, Phalanx III-1 is short and blocky, with ¯at 1984), in which digit I is short. The unguals medial and ventral faces that are set perpen- are slightly curved, not trenchant, and bear dicular to each other. As in phalanx II-1, the small ¯exor tubercles distal to the proximal medioventral end of the proximal articulation articulations as in other ornithomimosaurs extends for a short distance below the end of (OsmoÂlska, 1997; Sereno, 2001). In Galli- metacarpal III. Distally, the medial collateral mimus (OsmoÂlska et al., 1972), Struthiomi- ligament pit is very weak. The distal articu- mus (Osborn, 1917; Nicholls and Russell, lation is apparently ginglymoid. Phalanx III- 1985; AMNH 5339), Anserimimus (IGM 2 is almost identical to phalanx III-1, except 100/300), Pelecanimimus (PeÂrez-Moreno et for being more slender and lacking the short al., 1994), and Ornithomimus (Sternberg, heel on the proximal articulation. Phalanx 1933) the ungual of digit I reaches to at least III-3 is longer than the combined lengths of the base of the unguals of digits II and III. digits III-1 and III-2, as in derive ornithom- Only the distal part of metacarpal II is pre- imids (Barsbold and OsmoÂlska, 1990). Prox- served, and it is exposed in ventral and me- imally, phalanx III-3 is similar to II-2, in- dial views. The distal articulation is divided cluding the presence of a small tubercle just into two distinct tubercles ventrally. A pro- ventral to the proximal articulation. The shaft nounced ¯exor pit separates the two tuber- thins distally and is thinnest just adjacent to cles. Phalanx II-1 has a transversely ¯at ven- the distal articulation, which is offset ventral surface, with a pronounced arch in lateral trally from the shaft. The medial collateral view. The proximal articulation is extensive, ligament fossa is deep but not displaced dor- and a small posteromedial lappet forms a sally as in many other theropods. The ungual small heel extending ventral to the distal end is similar to those of digits I and II and is of the metacarpal. The distal articulation is roughly as long as that of digit II. It appears divided into two widely separated tubercles to have a more pronounced groove for the in ventral view, and the articulation appears claw sheath than do the other unguals. ginglymous, although it is poorly preserved. Phalanx II-2 is elongate, slender, and has HINDLIMB a nearly straight shaft that is oval in cross section. The proximal articulation is formed Both right and left femora are preserved; as a deep arc in lateral view, with dorsal and however, the right is severely damaged (®g. ventral parts of the articulation projecting far 10). The left femur lies in articulation with posteriorly. In contrast to Gallimimus, the the acetabulum, and proximal lateral and dis- ventral end of the articulation extends farther tal proximal surfaces are exposed. Hindlimb proximally than the dorsal tip. A small, mid- elements distal to the femur are not pre- line process or tuber is present on the ventral served. surface of the phalanx II-2, adjacent to prox- As in other ornithomimids, the femur is 16 AMERICAN MUSEUM NOVITATES NO. 3420

Fig. 12. Strict consensus of 432 most parsimonious trees depicting relationships among ornithomimosaur species derived from parsimony analysis of 220 characters in 50 coelurosaurian species (see http://research.amnh.org/users/norell/index.html). Tree statistics for shortest trees are (TL ϭ 586, CI ϭ 45, and RI ϭ75). Continental distributions are listed after taxon names. slightly bowed (contra Barsbold and OsmoÂl- dylar tuber is also present at the lateral apex ska, 1990), but not to the level of Manirap- of the lateral condyle. tora. The proximal end is exposed in lateral view. The greater trochanter is higher than GASTROLITHS the lesser trochanter. The lesser trochanter is alariform and is separated from the greater The thoracic cavity of Shenzhousaurus or- trochanter by a deep cleft that extends ap- ientalis contains numerous pebbles, which proximately 28 mm down the femoral shaft. are best interpreted as gastroliths. The uni- This cleft ends in the bump, which appar- form matrix surrounding the skeleton is de- ently does not continue down the femoral void of lithic clasts of a comparative size. shaft as the lateral ridge as in maniraptori- The pebbles are distributed unevenly in the forms like Velociraptor (Norell and Makov- thoracic cavity, with a concentration just an- icky, 1997, 1999). A small ridge divides the terior to the preserved part of the gastral bas- lesser trochanter into anterior and posteriorly ket. Less concentrated amounts of gastroliths oriented surfaces. A weakly developed fourth occur throughout the rest of the thoracic cav- trochanter lies distal and medial to the pos- ity, and some are dispersed posteriorly across terior trochanter. Distally the femur is twisted the femur and proximal end of the left ischium and sacrum. The gastroliths are hetero- to expose the posterior surface. The medial geneous in size, shape, and composition. condyle is much larger than the lateral one, Whereas some are smooth and rounded, oth- is bulbous, and extends medial to the axis of ers are highly angular and/or pockmarked. the femoral shaft. A thin crest, or buttress, Gastroliths have been previously reported in extends proximally up the shaft of the femur ornithomimosaurs (Kobayashi et al., 1999). from the medial condyle. The medial and lateral condyles are separated by a deep wide popliteal fossa that is not closed distally by DISCUSSION lateral or medial expansions. The gastrocne- Phylogenetic analysis posits Shenzhousau- mius process that lies posterior to the lateral rus near the base of Ornithomimosauria (Ma- condyle is unusual in that it is thin and its kovicky et al., in press), being more ad- lateral surface is nearly ¯at. It contacts the vanced than the Barremian Pelecanimimus shaft of the femur nearly at a right angle and (®g. 12). Ornithomimosaurs are monophylet- borders a ¯at, triangular surface on the fem- ic and are the sister group to a clade com- oral shaft that extends to the edge of the lat- posed of Maniraptora (including Ornitholes- eral condylar surface. A very low ectocon- tes) (Gauthier, 1986; Sereno, 1997; Xu et al., 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 17

2002b). No support was found for a close more progressive state in which maxillary relationship between ornithomimosaurs and teeth are absent and the dentary only bears troodontids (Holtz, 1994). Alvarezsaurids, teeth near the symphysis. which have been postulated as close orni- Although tooth loss is common among thomimosaur relatives (Sereno, 2001), are coelurosaurs (Chiappe et al., 1999), the pat- found to be the sister group of all other Man- tern is disparate among groups. Therizino- iraptora except Ornitholestes. Shenzhousau- sauroids and hesperornithiformes have eden- rus and other ornithomimosaurs are more de- tulous premaxillae, but retain maxillary and rived than Pelecanimimus in the progressive dentary teeth. Although advanced ovirapto- loss of teeth from the upper jaws and all but rosaurs are edentulous, the basal Caudipteryx the tip of the dentary (Shenzhousaurus, Har- has teeth restricted to the premaxilla. Nev- pymimus) or complete loss of teeth (higher ertheless, the ornithomimosaur pattern where ornithomimosaurs). Harpymimus and Shen- the lower jaw is toothed anteriorly and the zhousaurus are similar in having primitive entire upper jaw is edentulous appears manual proportions in which metacarpal I is unique as a phylogenetic precursor to tooth- much shorter than either II or III, but Har- lessness among theropod dinosaurs, with the pymimus shares a derived curvature of the possible exception of the basal avialan Shen- ischium with higher ornithomimids. zhouraptor (Ji et al., 2002b and 2003, Zhou Except for the Spanish taxon Pelecanimi- and Zhang, 2002). mus, most ornithomimids are known from Central Asia and western North America. ACKNOWLEDGMENTS Examining distributions within the context of We thank the National Geological Muse- the phylogeny (®g. 12) demonstrates that ear- um of China. Mick Ellison prepared the il- ly ornithomimids have an extensive evolu- lustrations, and Brian Roach prepared the tionary history in eastern Asia, yet the center specimen with the consultation of Marilyn of origin is ambiguous because of the Euro- Fox. The Division of Paleontology at the pean range of Pelecanimimus. Several other American Museum, Byron, Lynette, and dinosaur clades, including tyrannosaurs (Hutt Richard Jaffe, Vivian Pan, and the Field Mu- et al., 2001) and pachycephalosaurs (Sereno, seum Department of Geology provided sup- 1999), whose derived members are mainly port for this project. known from Asia and North America, also have basal taxa from the Early Cretaceous of REFERENCES Europe predating the formation of the Turgai Straits. Among higher ornithomimosaurs, a Barsbold R., and H. OsmoÂlska. 1990. Ornithom- single dispersal across Beringia is required to imosauria. In D.B. Weishampel, P. Dodson, and account for the distribution of taxa between H. OsmoÂlska (editors), The Dinosauria: 225± North America and Asia if North American 244. Berkeley: University of California Press. ornithomimids form a monophyletic taxon. Barsbold, R., and H. OsmoÂlska. 1999. The skull of Velociraptor (Theropoda) from the Late Cre- Otherwise, two dispersals are required to ex- taceous of Mongolia. Acta Palaeontologica Po- plain the known geographic diversity of this lonica 44(2): 189±219. clade. Barsbold, R., and A. Perle. 1984. The ®rst record Advanced ornithomimosaurs lack teeth of a primitive ornithomimosaur from the Cre- and had beaks (Osborn, 1917, Norell et al., taceous of Mongolia. Palaeontologicheskii 2001b). The edentulous nature of their beaks Zhurnal 1984(2): 121±122. [Translated from has been used along with gastroliths (Kobay- Russian] ashi et al., 1999) to suggest that the diet was Buffetaut, E., V. Suteethorn, and H. Tong. 1996. highly specialized. According to our phylo- The earliest tyrannosaur from the Lower Cre- genetic analysis, the advanced ornithomimid taceous of Thailand. Nature 381: 689±691. Chen, P.J., Z.-M. Dong, and S.-N. Zhen. 1998. An condition progressed through stages of loss exceptionally well preserved theropod dinosaur of the upper and posterior dentary teeth ini- from the Yixian Formation of China. Nature tially as seen in the reduced maxillary tooth- 391: 147±152. row in the basal form Pelecanimimus. Shen- Chiappe, L.M., M.A. Norell, and J.M. Clark. zhousaurus and Harpymimus illustrate a 1996. Phylogenetic position of Mononykus 18 AMERICAN MUSEUM NOVITATES NO. 3420

(Aves: Alvarezsauridae) from the Late Creta- Yuan, X.-X. Ji, J.-L. Li, and Y.-X. Li. 2002b. ceous of the Gobi Desert. Memoirs of the Discovery of an avialan bird, Shenzhouraptor Queensland Museum 39(3): 557±582. sinensis gen. et. sp. nov., from China. Geolog- Chiappe, L.M., S.-A. Ji, Q. Ji, and M.A. Norell. ical Bulletin of China 21(7): 363±369. [in Chi- 1999. Anatomy and systematics of the Confu- nese with English abstract] ciusornithidae (Theropoda: Aves) from the Late Ji., Q., S.-A. Ji, H.-L. You, J.-P. Zhang, N.-J. Mesozoic of northeastern China. Bulletin of the Zhang, C.-X. Yuan, and X.-X. Ji. 2003. An Ear- American Museum of Natural History 242: 1± ly Cretaceous Avialan bird Shenzhouraptor si- 89. nensis from Western Liaoning China. Acta Clark, J.M., M.A. Norell, and R. Barsbold. 2001. Geologica Sinica 77(1): 21±26. Two new oviraptorids (Theropoda: Ovirapto- Kobayashi, Y., J.-C. Lu, Z.-M. Dong, R. Barsbold, rosauria) from the Late Cretaceous Djadoktha Y. Azuma, and Y. Tomida. 1999. Herbivorous Formation, Ukhaa Tolgod, Mongolia. Journal diet in an ornithomimid dinosaur. Nature 402: of Vertebrate Paleontology 21(2): 209±213. 480. Currie, P.D., and X.-J. Zhao. 1993. A new car- Lo, C.-H., P.-J. Chen, Y.-Y. Tsou, S.-S. Sun, and nosaur (Dinosauria, Theropoda) from the Juras- C.-Y. Lee. 1999. 40Ar/39Ar laser single-grain sic of Xinjiang, People's Republic of China. and K-Ar dating of the Yixian Formation, NE Canadian Journal of Earth Sciences. 25: 972± China. Palaeoworld 11: 328±340. 986. Madsen, J.M. 1976. Allosaurus fragilis: a revised Gao, K., S. Evans, Q. Ji, M.A. Norell, and S.-A. osteology. Utah Geological Survey Bulletin 48: Ji. 2000. Exceptional fossil material of a semi- 27±31. aquatic reptile from China: the resolution of an Makovicky, P.J. 1995. Phylogenetic aspects of the enigma. Journal of Vertebrate Paleontology 20: vertebral morphology of Coelurosauria (Dino- 417±421. sauria: Theropoda). Unpublished M.S. disser- Gauthier, J.A. 1986. Saurischian monophyly and tation, Copenhagen University, Denmark. the origin of birds. In K. Padian (editor), The Makovicky, P.J., and M.A. Norell. 1998. A partial origin of birds and the evolution of ¯ight. ornithomimid braincase from Ukhaa Tolgod Memoirs of the California Academy of Scienc- (Upper Cretaceous, Mongolia). American Mu- es 8: 1±55. seum Novitates 3247: 1±16. Holtz, T.R., Jr. 1994. The phylogenetic position of the Tyrannosauridae: implications for theropod Makovicky, P.J., M.A. Norell, J.M. Clark, and T. systematics. Journal of Paleontology 68: 1100± Rowe. 2003. Osteology of Byronosaurus jaffei 1117. (Theropoda: Troodontidae). American Museum Hou, L. 1997. Mesozoic birds of China. Phoenix Novitates 3402: 1±32. Valley Provincial Aviary of Taiwan. 228 pp. Makovicky, P.J., Y. Kobayashi, and P.J. Currie. In Taipei. press. Ornithomimosauria. In D.B. Weisham- Hutt, S., D. Naish, D.M. Martill, M.J. Barker, and pel, P. Dodson, and H. OsmoÂlska (editors), The P. Newberry. 2001. A preliminary account of a Dinosauria: 2nd ed., Berkeley: University of new tyrannosauroid from the Wessex Forma- California Press. tion (Early Cretaceous) of southern England. Marsh, O.C. 1890. Description of New dinosau- Cretaceous Research 22: 227±242. rian reptiles. American Journal of Science (Se- Ji, Q., and S.-A. Ji 1996. On discovery of the ries 3) 39: 81±86. earliest bird fossil in China and the origin of Nicholls, E.L., and A.P. Russell. 1981. A new birds. Chinese Geology 17: 30±33. specimen of Struthiomimus altus from Alberta, Ji, Q., P.J. Currie, S.-A. Ji, and M.A. Norell. 1998. with comments on the classi®catory characters Two feathered dinosaurs from northeastern Chi- of upper Cretaceous ornithomimids. Canadian na. Nature 393: 753±761. Journal of Earth Sciences 18: 518±526. Ji, Q., Z.-X. Luo, and S.-A. Ji. 1999. A Chinese Nicholls, E.L., and A.P. Russell. 1985. Structure triconodont mammal and mosaic evolution of and function of the pectoral girdle and forelimb the mammalian skeleton. Nature 398: 326±330. of Struthiomimus altus (Theropoda: Ornithom- Ji. Q., S.-A. Ji, H.-B. Zhang, H.-L. You, J.-P. imidae). Palaeontology 28: 643±677. Zhang, L.-X. Wang, C.-X. Yuan, and X.-X. Ji. Norell, M.A., and P.J. Makovicky. 1997. Impor- 2002a. A new avialan bird, Jixiangornis orien- tant features of the dromaeosaur skeleton: in- talis gen. et sp. Nov. from the Lower Creta- formation from a new specimen. American Mu- ceous of western Liaoning, NE China. Journal seum Novitates 3215: 1±28. of Nanjing University (Natural Sciences) 38(6): Norell, M.A., and P.J. Makovicky. 1999. Impor- 723±736. tant features of the dromaeosaur skeleton II: in- Ji, Q., S.-A. Ji, H.-L. You, J.-P. Zhang, C.-X. formation from newly collected specimens of 2003 JI ET AL.: A TOOTHED ORNITHOMIMOSAUR 19

Velociraptor mongoliensis. American Museum dinosaurs. Annual Review of Earth and Plane- Novitates 3282: 1±45. tary Sciences 25: 435±489. Norell, M.A., P.J. Makovicky, and J.M. Clark. Sereno, P.C. 1999. The evolution of dinosaurs. 2000. A new troodontid from Ukhaa Tolgod, Science 284: 2137±2147. Late Cretaceous, Mongolia. Journal of Verte- Sereno, P.C. 2001. Alvarezsaurids: birds or orni- brate Paleontology Rapid Communication thomimosaurs? In J. A. Gauthier, and L.F. Gall 20(1): 7±11. (editors), New perspectives on the origin and Norell, M.A., J.M. Clark, and P.J. Makovicky. early evolution of birds: 69±98 New Haven, 2001a. Relationships among Maniraptora: CT: Peabody Museum of Natural History. problems and prospects. In J.A. Gauthier and Sternberg, C.M. 1933. A new Ornithomimus with L.F. Gall (editors), New perspectives on the or- complete abdominal cuirass. Canadian Field- igin and early evolution of birds: 49±67. New Naturalist 47(5): 80±83. Haven. CT: Peabody Museum of Natural His- Swisher, C.C., X.-L. Wang, Z.-H. Zhou, Y.-Q. tory. Wang, F. Jin, J.-Y. Zhang, X. Xu, F.-C. Zhang, Norell, M.A., P.J. Makovicky, and P.J. Currie. Y. Wang. 2002. Further support for a Creta- 2001b. The beaks of ostrich dinosaurs. Nature ceous age for the feathered dinosaur beds of 40 39 412: 873±874. Liaoning, China: new Ar/ Ar dating of the Osborn, H.F. 1903. Ornitholestes hermani, a new Yixian and Tuchengzhi Formations. Chinese compsognathid dinosaur from the upper Juras- Science Bulletin 47: 135±138. sic. Bulletin of the American Museum Natural Witmer, L.M. 1995. Homology of facial structures History 19: 459±464. in extant archosaurs (birds and crocodilians) Osborn, H.F. 1917. Skeletal adaptations of Orni- with special reference to paranasal pneumatic- tholestes, Struthiomimus, Tyrannosaurus. Bul- ity and nasal conchae. Journal of Morphology 225: 269±327. letin of the American Museum Natural History Witmer, L.M. 1997. The evolution of the antor- 35: 733. bital cavity of archosaurs: a study in soft-tissue OsmoÂlska, H. 1997. Ornithomimosauria. In P.J. reconstruction in the fossil record with an anal- Currie and K. Padian (editors), Encyclopedia of ysis of the function of pneumaticity. Society of Dinosaurs: 499±503. San Diego: Academic Vertebrate Paleontology Memoir 3: 1±73. Press. Xu, X., Z. Tang, and X. Wang. 1999a. A therizi- OsmoÂlska, H., E. Roniewicz, and R. Barsbold. nosaurid dinosaur with integumentary struc- 1972. A new dinosaur, Gallimimus bullatus n. tures from China. Nature 399: 350±354. gen., n. sp. (Ornithomimidae) from the Upper Xu, X., X. Wang, and X. Wu, 1999b. A dromaeo- Cretaceous of Mongolia. Palaeontologica Po- saurid dinosaur with a ®lamentous integument lonica 27: 103±143. from the Yixian Formation of China. Nature PeÂrez-Moreno, B.P., J.L. Sanz, A.D. Buscalioni, 401: 262±266. J.J. Moratalla, F. Ortega, and D. Rasskin-Gut- Xu, X., Z. Zhou, and X. Wang. 2000. The smallest man. 1994. A unique multitoothed ornithomi- known non-avian theropod dinosaur. Nature mosaur from the Lower Cretaceous of Spain. 408: 705±708. Nature 370: 363±367. Xu, X., M. A. Norell, X.-L. Wang, P. J. Makov- Perle, A., M.A. Norell, L.M. Chiappe, and J.M. icky, and X.-C. Wu. 2002a. A basal troodontid Clark. 1993. Flightless bird from the Creta- from the Early Cretaceous of China. Nature ceous of Mongolia. Nature 362: 623±626. 415: 780±784. Perle, A., L.M. Chiappe, R. Barsbold, J.M. Clark, Xu, X., Y.-N. Cheng, X.-L. Wang, and C.-H. and M.A. Norell. 1994. Skeletal morphology of Chang. 2002b. An unusual oviraptorosaurian Mononykus olecranus (Theropoda: Avialae) dinosaur from China. Nature 419: 291±293. from the Late Cretaceous of Mongolia. Amer- Zhou, Z., and F. Zhang, 2002. A long-tailed, seed- ican Museum Novitates 3105: 1±29. eating bird from the Early Cretaceous of China. Sereno, P.C. 1997. The origin and evolution of Nature 418: 405±409. Recent issues of the Novitates may be purchased from the Museum. Lists of back issues of the Novitates and Bulletin published during the last ®ve years are available at World Wide Web site http://library.amnh.org. Or address mail orders to: American Museum of Natural History Library, Central Park West at 79th St., New York, NY 10024. TEL: (212) 769-5545. FAX: (212) 769- 5009. E-MAIL: [email protected]

a This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper).