Turanoceratops tardabilis —the first ceratopsid dinosaur from Asia

Naturwissenschaften (2009) 96:645–652 DOI 10.1007/s00114-009-0518-9 SHORT COMMUNICATION Turanoceratops tardabilis—the first ceratopsid dinosaur from Asia Hans-Dieter Sues & Alexander Averianov Received: 21 December 2008 / Revised: 15 February 2009 / Accepted: 17 February 2009 / Published online: 10 March 2009 # US Government 2009 Abstract Turanoceratops tardabilis from the Upper Cre- Mongolia but rare in western North America (Ryan and taceous (Turonian) Bissekty Formation of Dzharakuduk, Currie 1998; You and Dodson 2004). Thus, an important Uzbekistan, represents the first definite ceratopsid dinosaur issue of dinosaurian biogeography is whether the Ceratop- recorded from Asia. Reexamination of the original and sidae originated in North America or whether they first study of newly collected material indicate that Turanocera- evolved in Asia and subsequently immigrated to North tops has well-developed supraorbital horns and apparently America via Beringia. lacks a nasal horn. Turanoceratops is more derived than the A critical taxon for addressing this question is Turano- more or less coeval Zuniceratops from the Moreno Hill ceratops tardabilis from the Upper Cretaceous (Turonian) Formation of New Mexico in the presence of double-rooted Bissekty Formation of Dzharakuduk in the central Kyzyl- teeth and of two or three teeth in each vertical dental file. kum Desert of Uzbekistan. The original description of this taxon was based on an incomplete maxilla, horn core Keywords Dinosauria . Ceratopsidae . Cretaceous . Asia fragments, and isolated teeth (Nessov et al. 1989). Turanoceratops was assigned to the Ceratopsidae and more specifically to Monocloniinae (Nessov et al. 1989) or Introduction Centrosaurinae (Nessov 1995). Some later authors have accepted placement of Turanoceratops as a ceratopsid or at Derived horned dinosaurs (Ceratopsidae) were a diverse least the sister-taxon to Ceratopsidae (Sereno 1997, 2000; clade of dinosaurs that appeared relatively late during the Chinnery and Weishampel 1998; Wolfe and Kirkland 1998) evolutionary history of nonavian dinosaurs and has long whereas others (You and Dodson 2003, 2004; Dodson et al. been considered endemic to western North America. This 2004) dismissed Turanoceratops as a nomen dubium and distribution is in a marked contrast with that of more basal considered Ceratopsidae exclusively North American in ceratopsians (Psittacosaurus, Protoceratops, and related distribution. The principal reason for the latter point of view taxa), which are abundant and diverse in China and was the tantalizingly incomplete nature of original material assigned to Turanoceratops. Here, we report on additional remains of T. tardabilis from the type locality, which provide critical new information on the phylogenetic Communicated by G. Mayr position of this taxon. H.-D. Sues National Museum of Natural History, Smithsonian Institution, Institutional abbreviations MRC 106, P.O. Box 37012, Washington, DC 20013-7012, USA e-mail: [email protected] CCMGE, Chernyshev’s Central Museum of Geological A. Averianov (*) Exploration, Saint Petersburg, Russia; USNM, National Zoological Institute, Russian Academy of Sciences, Museum of Natural History, Smithsonian Institution, Universitetskaya nab. 1, Saint Petersburg 199034, Russia Washington, DC, USA; ZIN PH, Paleoherpetological e-mail: [email protected] Collection, Zoological Institute, Russian Academy of 646 Naturwissenschaften (2009) 96:645–652 Sciences, Saint Petersburg, Russia. The specimens previ- Anatomical description ously reported by Nessov et al. (1989) and Nessov (1995) are housed in the CCMGE collection; the newly collected Nessov designated an incomplete left maxilla (CCMGE specimens are deposited in the ZIN PH and USNM 251/12457; Fig. 1a–c) as the holotype of T. tardabilis. This collections. specimen is broken into two tightly fitting pieces. The maxilla preserves 11 alveoli, three of which still contain teeth; alveolus 4 contains an erupting replacement tooth, Systematic paleontology and alveoli 6 and 9 each hold functional teeth. The first alveolus is small, but, starting at the second, the alveoli Dinosauria Owen 1842 increase in size toward the posterior end of the tooth row, Ornithischia Seeley 1887 which turns posterolaterally in occlusal view. Anterior to Ceratopsidae Marsh 1888 the first alveolus, the maxilla forms a sharp edge that curves T. tardabilis Nessov and Kaznyshkina in Nessov et al. anterolaterally for a short distance before reaching a now- 1989 broken surface. The labial surface of the dorsoventrally Ceratopsidae [indet.]: Riabinin 1931: pl. 2, Fig. 7; deep maxilla overhangs the tooth row. The anterodorsal Nessov 1986: Fig. 2–4. portion of the bone is concave and at least partially T. tardabilis [nomen nudum]: Nessov 1988: 97. preserves the contact area with the premaxilla. This T. tardabilis: Nessov et al. 1989: 149, pl. 1, Figs. 16–21; concave area in CCMGE 251/12457 resembles a Nessov 1995: 55, pl. 7, Figs. 1–9, 11, 15–21; Nessov 1997: corresponding feature on the maxilla of Brachyceratops pl. 20, Figs. 20–21. (USNM 14765). A second maxillary fragment (ZIN PH 303/16; Fig. 1d, e) Holotype is poorly preserved, but the broken alveolar margin reveals the presence of at least two teeth in each dental file. In the CCMGE 251/12457, incomplete left maxilla (Fig. 1a–c). posteriormost preserved dental file, the apex of the not yet functional replacement tooth is 7.5 mm above the preserved Type locality and horizon ventral border of the maxilla. Its two roots are widely separated and surround a smaller replacing tooth germ. Locality CBI-27, Dzharakuduk, Navoi Viloyat (district), Thus, the number of replacing teeth in the dental files in central Kyzylkum Desert, Uzbekistan. Lower part of the Turanoceratops can be established as two or three. Lingual Bissekty Formation. Age: Late Cretaceous: middle-late to the third replacing tooth in the last file, there are two Turonian. Unlike for most dinosaur-bearing strata of “special foramina” associated with dental lamina. A distinct Cretaceous age from Asia, the age of the Bissekty facet dorsal to the three posterior dental files formed the Formation can be well constrained due to its intercalation contact with the ectopterygoid. with marine strata (King et al., in review). A right postorbital ZIN PH 1868/16 preserves a complete supraorbital horn core (Fig. 3a, b). A short but Referred material distinct prefrontal facet is present along the orbital margin at the anteromedial corner of the horn base. The bony Maxilla fragment, postorbital with supraorbital horn, margin medial to the prefrontal facet apparently represents isolated supraorbital horn cores, possibly frill fragments, the contact area with the frontal. The rugose sutural contact predentary, isolated teeth, distal portion of humerus, distal is confined to the dorsal margin whereas the ventral margin ends of tibiae with fused astragali, and fourth metatarsal, all is occupied by a concave smooth area, possibly forming the from Dzharakuduk. wall of a frontal sinus (Forster 1996: Fig. 5). Alternatively, the rugose dorsal area may represent the broken surface of Revised diagnosis the co-ossified frontal. The posteromedial corner of the postorbital is formed by a prominent knob-like rugose Differs from more derived ceratopsids in the presence of articular condyle, apparently for contact with the parietal. variably developed secondary ridges on the tooth crowns On the dorsal surface, this condyle is surrounded by a strap- and only two or three teeth in each vertical dental file. shaped smooth depression (termed “sulcus” in other Differs from Zuniceratops in the presence of double-rooted ceratopsids), which is divided into three concavities. If the teeth and two or three teeth in each dental file. Differs from ceratopsid “sulcus” corresponds to the frontoparietal de- more basal neoceratopsians in the exclusion of the frontal pression of basal neoceratopsians, this part of the bone may from the orbital margin, presence of a shallow supracranial represent a frontal fragment co-ossified with the postorbital. cavity complex, and double-rooted teeth. A thin and curved articular surface lateral to the condyle Naturwissenschaften (2009) 96:645–652 647 Fig. 1 Jaw fragments of T. tardabilis from the Upper Cretaceous (Turonian) Bissekty Formation of Dzharakuduk, Uzbekistan. a–c CCMGE 251/ 12457 (holotype), incomplete left maxilla in medial (a), ventral (b), and posterior (c) views. d, e ZIN PH 303/16, fragment of right maxilla in lateral (d) and posterior (e) views. f–h CCMGE 255/12457, incomplete predentary in dorsal (j), lateral (k), and ventral (l) views. ect ectopterygoid facet, ft functional tooth, rt replacing tooth. Scale bars equal 10 mm and “sulcus” might have contacted the squamosal, and a dorsolaterally, as in Zuniceratops (Wolfe and Kirkland small triangular ventral articular surface might be for 1998: Fig. 7) and Chasmosaurus (Dodson et al. 2004: contact with the laterosphenoid. The posterolateral and Fig. 23.2C, D) but unlike the ventrolateral curvature found posterior margins of the orbit are incomplete. The supraor- in most other ceratopsids. The total height of the horn is bital horn rises immediately above orbit and has a flattened about 140 mm from the orbital margin. Vascular grooves lateral surface, as in Zuniceratops (Wolfe and Kirkland extend along the anterolateral surface of the horn core and a 1998). It is anterolaterally directed, about 60×47 mm at its single longitudinal groove is developed on the posterior base and rapidly tapers toward the apex. It curves aspect; the medial surface of the horn is rather smooth. 648 Naturwissenschaften (2009) 96:645–652 There are additional smaller fragments of supraorbital horn well as at the base of the crown; these features are not cores, such as CCMGE 256/12457, which is more coarsely found in hadrosauroid teeth. The enamel covering on tooth striated than ZIN PH 1868/16. crowns of Turanoceratops is somewhat more wrinkled than The predentary CCMGE 255/12457 (Fig. 1f–h) is on the hadrosauroid teeth. The crown is sharply recumbent slightly damaged. It is triangular in dorsal and ventral relative to the long axis of the root. The roots of teeth of view. The ventral surface of the predentary is divided by a Turanoceratops are divided, with a figure-eight outline in median ridge into two ventrolaterally facing surfaces, which transverse section basally, but only a single known tooth are covered by a network of deep vascular grooves. It completely preserves two distinct roots (CCMGE 11/ slopes gently posteriorly from the anterior end. The dorsal 12454; Nessov 1986: Fig.2–4; Nessov et al. 1989, pl. 1, edges of the predentary are thick and form dorsolaterally Fig. 16; Nessov 1995: pl. 7, Fig. 1; catalogue number facing rather than flat surfaces that bear foramina. In lateral incorrectly given as CCMGE 252/12457 in those publica- view, they are gently concave anteroposteriorly. The tions). The root has pronounced asymmetrical mesial and anterodorsal end of the predentary is damaged. The medial distal depressions for adjacent tooth crowns. Due to the portion of the bone is deeply concave transversely. The absence of typical “resorption” facets, it is difficult to greatest length of the predentary as preserved is 115 mm, distinguish maxillary and dentary teeth of Turanoceratops. and its greatest width posteriorly is 73 mm. In both types of teeth, the crown is asymmetrical, with the Isolated teeth of Turanoceratops (Fig. 2) can be easily median carina placed much closer to one side of the crown, distinguished from the common teeth of hadrosauroid and secondary ridges may be present. The secondary ridges ornithopods at Dzharakuduk by the absence of a “resorp- are much finer than the median carina; one or two such tion” facet on the lingual side of the root for the replacing ridges may extend basally toward the base of the crown. tooth. In contrast to the condition in hadrosauroid teeth, The marginal denticles are less prominent than those on resorption occurs between the roots (Fig. 2f). Furthermore, hadrosauroid teeth, being merely the apices of the second- the crowns on teeth of Turanoceratops are the widest at the ary ridges along the edge of the crown. The wear facets are base and do not extend basally onto the root beyond this inclined at an angle of about 15° to the horizontal plane, widest point, whereas in both maxillary and dentary teeth of which is less steep than that on hadrosauroid teeth. The hadrosauroids, the enamel covering extends basally onto enamel usually covers only one side of the crown, but in the root beyond the widest part of the crown. Tooth crowns some small possibly juvenile teeth (e.g., ZIN PH 1882/16, of Turanoceratops frequently have deep pockets along the Fig. 2i), the enamel also covers the apex of the non- mesial and distal edges (lateral depressions in Fig. 2) as enameled side of the crown. Fig. 2 Isolated teeth of T. tardabilis from the Upper Cretaceous (Turonian) Bissekty Formation of Dzharakuduk, Uzbekistan. a, b ZIN PH 2322/ 16, in mesial/distal (a) and labial/lingual (b) views. c ZIN PH 2318/16, in labial/lingual view. d ZIN PH 2319/16, in labial/lingual view. e, f ZIN PH 2321/16, in mesial/distal (e) and labial/lingual (f) views. g–i ZIN PH 1882/16, in labial/ lingual (g, i) and mesial/distal (h) views. en enamel covering nonenameled crown side, ld lateral depression, mc median carina, res resorption, sr secondary ridge. Scale bars equal 3 mm for a–f and 1 mm for g–i Naturwissenschaften (2009) 96:645–652 649 A few isolated single-rooted teeth, interpreted by Nessov Triceratops, USNM 508518). The articular surface of the (1995) as being derived either from the mesial or distal end spherical radial condyle extends onto the ventral (anterior) of the tooth row of Turanoceratops, appear referable to a surface of the humerus. The ulnar condyle is damaged protoceratopsian. A poorly preserved maxilla CCMGE 514/ distally and laterally. The olecranon fossa is shallow. There 12457 (Nessov 1995: pl. 5, Fig. 20) is the only other known are no epicondyles. bone from Dzharakuduk that is referable to this protocer- Two distal portions of tibiae with fused astragali have atopsian; it is similar in size to maxillae of the Cenomanian been recovered to date. The more complete is USNM Asiaceratops (Nessov et al. 1989). The postcranial bones 538130 (Fig. 3f). Fusion of the tibia and astragalus is described below are much larger, more massive, and differ present in both ankylosaurs (Coombs 1979) and ceratop- in structure from the corresponding bones of adult sids, and thus assignment of ZIN PH 1444/16 and USNM Asiaceratops. Thus, their attribution to the Dzharakuduk 538130 to Turanoceratops must remain tentative. Refer- protoceratopsian is unlikely. ence to Ceratopsia is based on direct comparison with the CCMGE 9/3760 is the distal end of a left humerus tibia of Triceratops (USNM 508518). The border between (Fig. 3c–e). It was one of the first dinosaurian bones ever the astragalus and tibia is marked by a series of foramina. reported from Dzharakuduk and Riabinin (1931) used it to The distal end is greatly expanded mediolaterally, with the establish the presence of Ceratopsidae at this locality. We lateral malleolus distinctly more expanded than the medial accept Riabinin’s identification of CCMGE 9/3760 based malleolus. The anterior side of the distal end is concave. on the close resemblance of this specimen to the humeri of This concavity continues to the short but wide canal Ceratopsidae (e.g., Hatcher et al. 1907: pls. 11, 12; Lehman between the tibia and astragalus near the possible contact 1989: Fig. 16A–C; Dodson et al. 2004: Fig. 23.6G–J; with the calcaneum (Fig. 3f). As far as we know, such a Fig. 3 Postorbital and limb bones of T. tardabilis from the Upper Cretaceous (Turonian) Bisskety Formation of Dzhara- kuduk, Uzbekistan. a, b ZIN PH 1868/16, right postorbital with supraorbital horn core in dorsal (a) and medial (b) views. c–e CCMGE 9/3760, distal end of left humerus in lateral (c), posterior (d), and distal (e) views. f USNM 538130, distal end of right tibia with fused astragalus in anterior view. g ZIN PH 342/16, left metatarsal IV in anterior view. ac articular condyle, ast astragalus, can canal, fsi frontal sinus, fsu frontal suture, prf prefrontal facet, rc radial condyle, sh supraorbital horn, sul sulcus, uc ulnar condyle. Scale bars each equal 10 mm 650 Naturwissenschaften (2009) 96:645–652 canal has previously not been reported, but a distinct gently concave medial and lateral margins. The anterior groove on the anterior surface of tibia at junction with the surface of the shaft is flat to slightly concave; the posterior astragalus in some ankylosaurs (Coombs 1979: Fig. 5A) surface is convex and bears a longitudinal median ridge. On and ceratopsids (Marsh 1890: pl. 58, Fig. 2; Hatcher et al. the anterior surface, a small pit is present just proximal to 1907: Fig. 71B, pl. 16, Fig. 1; USNM 508518) may lead to the distal condyle. The distal condyle is slightly gingly- such a canal. On the posterior side, a prominent vertical moid, with the articular surface continuous anteriorly and ridge extends closer to the medial edge. The posterior separated by a short furrow posteriorly. There is a shallow surface is flat medial and concave lateral to this ridge. lateral depression for the collateral ligament; the medial The astragalus is preserved on the two aforementioned distal condyle is damaged. tibia fragments where it is fused to the distal end of the tibia; it is complete in USNM 538130 (Fig. 3f). The astragalus is a thin trapezoidal plate with the posterior side Phylogenetic analysis and discussion longer than the anterior one. The distal surface is saddle- shaped, concave transversely, and convex anteroposteriorly. The currently known hypodigm for T. tardabilis can only The anterolateral corner of the bone forms a hook-like be coded for 18 out of 133 characters listed in the character– process, which overhangs the groove on the anterior side of taxon matrix for Ceratopsia compiled by Makovicky and the adjacent tibia. Norell (2006)—22(0), 24(0), 31(1), 32(1), 68(1), 69(1), 71 We identify ZIN PH 342/16 (Fig. 3g) as a left fourth (2), 95(1), 96(1), 97(1), 98(2), 99(0), 100(1), 101(0/1), 102 metatarsal of Turanoceratops based on its close similarity (1), 103(0), 105(1), and 106(1). The data matrix including to the fourth metatarsal of Avaceratops (Penkalski and information for Turanoceratops was analyzed using NONA Dodson 1999: Fig. 10E, F) and other ceratopsids (Brown version 2.0 (Goloboff 1999) with the WinClada version 1917: pl. 12, Fig. G; Lull 1933: Fig. 29). The rugose 1.00.08 interface (Nixon 1999). One thousand repetitions of proximal articular surface of this bone is trapezoidal in the parsimony ratchet (island hopper) algorithm generated proximal view; its lateral half extends further distally than two equally most parsimonious trees, each with a tree the medial half. Along the medial side of the proximal end, length of 221 steps, a consistency index of 0.70, and a there is a facet for contact with the third metatarsal. The retention index of 0.80. The strict consensus tree is shown proximal end of the metatarsal is wide mediolaterally. The in Fig. 4. Turanoceratops is nested within Ceratopsidae shaft of the bone is constricted between the epiphyses, with and placed as the sister-taxon to Centrosaurinae. Nessov Fig. 4 Strict consensus tree of two most parsimonious trees produced optimized characters are shown (black circles indicate nonhomopla- by ratchet (island hopper) algorithm of NONA 2.0 using the sies and white circles homoplasies). The numbers at the circles are character–taxon matrix compiled by Makovicky and Norell (2006) characters (above) and states (below) with addition of character states for T. tardabilis. Only unambiguously Naturwissenschaften (2009) 96:645–652 651 (1995: 54) apparently referred Turanoceratops to the ceratops resemble those of the North American protocer- Centrosaurinae rather than to the Ceratopsinae (= Chasmo- atopsid Leptoceratops (Ryan and Currie 1998). Apparently, saurinae) because he considered the supraorbital horns this represents a level of specialization intermediate poorly developed relative to the nasal horn in this taxon between basal neoceratopsians and derived ceratopsids, (see his reconstruction of the skull of Turanoceratops; somewhat blurring the dental distinction between these two Nessov 1995: Fig. 4). ZIN PH 1868/16 shows that the groups. The discovery of such a transitional ceratopsian supraorbital horns in Turanoceratops were, in fact, well taxon in Asia brings into question the traditional scenario of developed. a North American origin of the clade Ceratopsoidea Nessov referred the incomplete braincase CCGME 628/ (Leptoceratopsidae+Ceratopsidae; You and Dodson 2003). 12457 (Nessov 1995: Fig. 5) to Turanoceratops but this However, we cannot rule out the possibility that Turano- specimen belongs to a sauropod dinosaur (Sues et al., ceratops was a North American immigrant to Asia, while unpublished data). Nessov (1995) interpreted CCMGE 723/ the clade mainly diversified in North America. The limited 12457 as the medial bridge of the frill (parietal) of record of the Late Cretaceous coastal floodplain environ- Turanoceratops; however, we have reidentified this bone ments in Asia, which would have provided suitable habitats as an ankylosaurian osteoderm. We were unable to relocate for ceratopsid dinosaurs, may be the principal reason for the the squamosals CCMGE 717 and 718/12457 reported by rarity of this group on that continent. Nessov (1995) in the CCMGE and ZIN collections. An incomplete horn core CCMGE 254/12457, interpreted by Acknowledgments Fieldwork for this study was funded by grants Nessov et al. (1989) and Nessov (1995) as a nasal horn, is from the National Science Foundation (EAR-9804771 and 0207004) flattened on one side. Thus, it more likely represents a and National Geographic Society (5901-97 and 6281-98) to J. D. Archibald and H.-D.S. and US Civilian Research and Development supraorbital horn core, and the presence of a nasal horn in Foundation grant RUB1-2860-ST-07 to A.A. and J. D. Archibald. We Turanoceratops cannot be verified from the existing thank the National Academy of Sciences of Uzbekistan, especially material. D. A. Azimov, director of the Institute of Zoology, for continued Dodson et al. (2004: 510) considered T. tardabilis a collaboration and assistance. M. J. Ryan and an anonymous reviewer provided helpful suggestions on a draft of the manuscript. nomen dubium with reference to unpublished comments by Makovicky that “the teeth are single-rooted as in non- ceratopsid ceratopsians and … that the supraorbital horn may conceivably belong to a thyreophoran.” However, this References statement is contradicted by the fact that the teeth in the holotype maxilla of T. tardabilis are clearly double-rooted Brown B (1917) A complete skeleton of the horned dinosaur Monoclonius, and description of a second skeleton showing skin as in more derived ceratopsids. Isolated ceratopsid teeth impressions. Bull Am Mus Nat Hist 37:281–306 with double roots are common at Dzharakuduk. The horn Chinnery BJ, Weishampel DB (1998) Montanoceratops cerorhynchus core fragments described by Nessov were correctly (Dinosauria: Ceratopsia) and relationships among basal neo- assigned to Turanoceratops and are unlike any thyreo- ceratopsians. J Vert Paleontol 18:569–585 Coombs WP Jr (1979) Osteology and myology of the hindlimb in the phoran osteoderms known to us. Finally, a recently Ankylosauria. J Paleontol 53:666–684 collected postorbital (ZIN PH 1868/16) preserves a com- Dodson P, Forster CA, Sampson SD (2004) Ceratopsidae. In: plete supraorbital horn (Fig. 3a, b) and is unquestionably Weishampel DB, Dodson P, Osmólska H (eds) The Dinosauria, ceratopsid. We consider Turanoceratops a valid taxon. It 2nd edn. University of California Press, Berkeley, pp 494–513 Forster CA (1996) New information on the skull of Triceratops. J Vert resembles Zuniceratops from the Moreno Hill Formation of Paleontol 16:246–258 New Mexico in the direction and structure of the Goloboff P (1999) NONA (No Name) version 2. Published by the author, supraorbital horn but is more derived than the latter one Tucumán, Argentina. Available online at www.cladistics.org in having double-rooted teeth as well as two or three teeth Hatcher JB, Marsh OC, Lull RS (1907) The Ceratopsia. US Geol Surv Monogr 49:1–300 in each vertical dental file. Zuniceratops is currently Lehman TM (1989) Chasmosaurus mariscalensis, sp. nov., a new considered a nonceratopsid basal neoceratopsian (You and ceratopsian dinosaur from Texas. J Vert Paleontol 9:137–162 Dodson 2004). Turanoceratops shares at least three Lull RS (1933) A revision of the Ceratopsia or horned dinosaurs. characters considered diagnostic for Ceratopsidae by Mem Peabody Mus Nat Hist Yale Univ 3(3):1–175 Makovicky PJ, Norell MA (2006) Yamaceratops dorngobiensis, a new Dodson et al. (2004): (1) frontal excluded from orbital primitive ceratopsian (Dinosauria, Ornithischia) from the Creta- margin, (2) presence of shallow supracranial cavity com- ceous of Mongolia. Am Mus Novit 3530:1–42 plex, and (3) teeth with two roots. Turanoceratops is more Marsh OC (1888) A new family of horned dinosaurs from the plesiomorphic than more derived, large-bodied ceratopsids Cretaceous. Am J Sci (3) 36:477–478 Marsh OC (1890) Additional characters of the Ceratopsidae, with in having variably developed secondary ridges on the tooth notice of new Cretaceous dinosaurs. Am J Sci (3) 39:418–426 crowns and only two or three (rather than four or five) teeth Nessov LA (1986) First discovery of the Late Cretaceous bird in each vertical dental file. The tooth crowns of Turano- Ichthyornis in the Old World and some other bones of birds 652 Naturwissenschaften (2009) 96:645–652 from the Cretaceous and Paleogene of Middle Asia. Trudy Zool Riabinin AN (1931) On dinosaurian remains from the Upper Inst AN SSSR 147:31–38 In Russian Cretaceous of the lower parts of Amu-Daria River. Zap Russ Nessov LA (1988) Assemblages of vertebrates of the late Mesozoic Min Obshch (2) 60:114–118 In Russian and Paleocene of Middle Asia. Trudy XXXI Sess Vsesoyuz Ryan M, Currie PJ (1998) First report of protoceratopsians (Neo- Paleont Obshchestva. Nauka, Leningrad, pp 93–101 In ceratopsia) from the Late Cretaceous Judith River Group, Russian Alberta, Canada. Can J Earth Sci 35:820–826 Nessov LA (1995) Dinosaurs of northern Eurasia: new data about Seeley HG (1887) On the classification of the fossil animals assemblages, ecology and paleobiogeography. Izdatelstvo Sankt- commonly named Dinosauria. Proc R Soc Lond 43:165–171 Peterburgskogo Universiteta, St. Petersburg In Russian Sereno PC (1997) The origin and evolution of dinosaurs. Ann Rev Nessov LA (1997) Cretaceous nonmarine vertebrates of northern Earth Planet Sci 25:435–489 Eurasia. Izdatel’stvo Sankt-Peterburgskogo Universiteta, Saint Sereno PC (2000) The fossil record, systematics and evolution of Petersburg In Russian pachycephalosaurs and ceratopsians from Asia. In: Benton MJ, Nessov LA, Kaznyshkina LF, Cherepanov GO (1989) Ceratopsian Shishkin MA, Unwin DM, Kurochkin EN (eds) The age of dinosaurs and crocodiles of the Mesozoic of Middle Asia. In: dinosaurs in Russia and Mongolia. Cambridge University Press, Bogdanova TN, Khozatsky LI (eds) Theoretical and applied Cambridge, pp 480–516 aspects of modern paleontology. Nauka, Leningrad, pp 144–154 Wolfe DG, Kirkland JI (1998) Zuniceratops christopheri n. gen., n. In Russian sp., a ceratopsian dinosaur from the Moreno Hill Formation Nixon KC (1999) WinClada version 1.0000. Published by the author, (Cretaceous, Turonian) of west-central New Mexico. New Ithaca, NY. Available online at www.cladistics.org Mexico Mus Nat Hist Sci Bull 14:303–317 Owen R (1842) Report on British fossil reptiles. Part II. Rep Brit Ass You HL, Dodson P (2003) Redescription of neoceratopsian dinosaur Adv Sci 1841:60–204 Archaeoceratops and early evolution of Neoceratopsia. Acta Penkalski P, Dodson P (1999) The morphology and systematics of Palaeont Pol 48:261–272 Avaceratops, a primitive horned dinosaur from the Judith River You HL, Dodson P (2004) Basal Ceratopsia. In: Weishampel DB, Formation (late Campanian) of Montana, with the description of Dodson P, Osmólska H (eds) The Dinosauria, 2nd edn. a second skull. J Vert Paleontol 19:692–711 University of California Press, Berkeley, pp 478–493