Cretaceous Research 35 (2012) 69e80
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New leptoceratopsids from the Upper Cretaceous of Alberta, Canada Michael J. Ryan a, *, David C. Evans b, c, Philip J. Currie d, Caleb M. Brown c, Don Brinkman e a
Department of Vertebrate Paleontology, 1 Wade Oval Drive, University Circle, Cleveland Museum of Natural History, Cleveland, OH 44106, USA Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario M5S 2C6, Canada c Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada d Department of Biological Sciences, University of Alberta, CW 405 Biological Sciences Building, Edmonton, Alberta T6G 2E9, Canada e Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta T0J 0Y0, Canada b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 July 2011 Accepted in revised form 25 November 2011 Available online 2 December 2011
Two new leptoceratopsid neoceratopsians are described based on partial dentaries collected from the Dinosaur Park (Campanian) and Milk River (Santonian) formations of Alberta. The new Campanian taxon has a unique dentary tooth shape not shared by other leptoceratopsid taxa, which has implications for the evolution of the Leptoceratopsidae. The Santonian specimen represents the oldest known leptoceratopsid (w83 Ma), and probably represents the smallest adult-sized ceratopsian known from North America. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Ceratopsia Leptoceratopsidae Campanian Santonian Systematics Evolution
1. Introduction In 1998, Ryan and Currie reported on the first recorded nonceratopsid neoceratopsian elements from the middle Campanian Dinosaur Park Formation of Alberta, including a partial right dentary and an almost complete left dentary. These remains were originally referred to Leptoceratops sp. At that time, the basal neoceratopsian record (excluding isolated teeth) from Late Cretaceous deposits in North America was limited to the Maastrichtian occurrences of Montanoceratops cerorhynchus Sternberg, 1951 from the St. Mary’s River Formation of Montana, and Leptoceratops gracilis Brown, 1914 from the Scollard Formation of Alberta (Brown, 1914; Sternberg, 1951). Recent work has added to the number of basal neoceratopsian taxa known from the Upper Cretaceous of North America and has clarified both the referral of some problematic specimens, and their host formations. Chinnery (2004) and Chinnery and Horner (2007) described Prenoceratops pieganensis and Cerasinops hogkissi, respectively, from the Campanian portion of the Two Medicine Formation of Montana. Miyashita et al. (2010) referred a frontal from the Devil’s Coulee locality of the Oldman Formation of southern Alberta to Prenoceratops sp. Makovicky (2001) identified a braincase (AMNH 5244) of Montanoceratops
* Corresponding author. E-mail addresses:
[email protected],
[email protected] (M.J. Ryan). 0195-6671/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2011.11.018
from the Maastrichtian beds of the upper Horseshoe Canyon Formation of Alberta; however, the exact locality for the quarry of this specimen is unknown and it may have been collected from the Scollard Formation, which also has extensive exposure in the area. A review of Montanoceratops by Makovicky (2010), building on work by Chinnery and Weishampel (1998), highlighted important information about the skeleton of Montanoceratops including the fact that the nasal is unknown for the taxon. Miyashita et al. (2010) clarified that the provenance of TMP 82.11.1, a partial neoceratopsian skeleton referred to Montanoceratops, is derived from the Willow Creek Formation (Maastrichtian), rather than the Campanian Belly River Group of Alberta as suggested by Ryan and Currie (1998). Makovicky (2010) suggested that TMP 82.11.1 represents an indeterminate leptoceratopsid that cannot be referred to Cerasinops, Montanoceratops or Leptoceratops, but which may have affinities with Prenoceratops. Most recently, Leptoceratops has been identified from the Hell Creek Formation of Montana (Ott, 2006). This new information on the diversity and biostratigraphy of Late Cretaceous basal neoceratopsians from North America allows reassessment of the original referral of TMP 95.12.6 to the genus Leptoceratops. As previously noted by Chinnery (2004), TMP 95.12.6 cannot be referred to Leptoceratops or Prenoceratops. Makovicky (2010) concurred, and further suggested that the specimen is also not referable to Cerasinops or Montanoceratops. Key anatomical characters of TMP 95.12.6 are reappraised here and incorporated into a numerical phylogenetic analysis for the first time. Results
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indicate that TMP 95.12.6 is distinct from all other leptoceratopsids, and is erected as a new taxon based on the originally described material. A partial right dentary from the Santonian Milk River Formation represents the oldest known leptoceratopsid, and is also referred to a new taxon. Institutional abbreviations. ANMH, American Museum of Natural History; MNHCM, Mokpo Natural History and Culture Museum, Korea; MOR, Museum of The Rockies; PIN, Paleontological Institute, Russian Academy of Sciences; ROM, Royal Ontario Museum; TMP, Royal Tyrrell Museum of Palaeontology; USMN, United States National Museum; ZCDM, Zhucheng Dinosaur Museum, China. 2. Systematic paleontology Dinosauria Owen, 1842 Ornithischia Seeley, 1887 Ceratopsia Marsh, 1888 Neoceratopsia Sereno, 1986 Leptoceratopsidae Makovicky, 2001 Unescoceratops gen. nov. Type species. Unescoceratops koppelhusae gen. et. sp. nov. Derivation of generic name. UNESCO refers to the World Heritage Site designation conferred upon the holotype locality (Dinosaur Provincial Park, Alberta) by the United Nations Educational, Scientific and Cultural Organization, and “ceratops”, from the Greek meaning “horned face”. Diagnosis. Unescoceratops, gen. nov. differs from Cerasinops, Leptoceratops, Prenoceratops, Udanoceratops, and Zhuchengceratops in having a gentle rather than pronounced curvature of the ventral margin of the dentary, and from Montanoceratops, which has a straight ventral margin. Unescoceratops shares with Leptoceratops and Prenoceratops the flange-like anteroventral margin of the predentarydentary symphysial surface, but differs from them in having this flange
developed as a small “chin” projecting below the ventral margin. Additionally, in Prenoceratops, the flange is separated from the ventral margin by a notch. Unescoceratops is similar to Leptoceratops, Montanoceratops, and Zhuchengceratops in having a dentary that is deeper anteriorly than it is posteriorly (Chinnery and Weishampel, 1998), but the presence of the chin gives its dentary a distinct hatchet-shape when viewed laterally. Unescoceratops shares with Cerasinops a distinctly recumbent coronoid process, but it can be differentiated from this taxon in having the contacts for the surangular and articular being positioned more posteriorly below the coronoid process. It differs from all other leptoceratopsids for which the teeth are known in that the teeth from the middle region of the dentary are as wide as high and have a rounded lingual profile with marginal denticles that extend almost to the root. The dentary teeth of other leptoceratopsids are much taller than wide, have vertical mesial edges, with the denticles on the mesial edge restricted to the top of the tooth. Unescoceratops koppelhusae sp. nov. Fig. 1 Holotype. TMP 95.12.6, a partial left dentary (Fig. 1). Derivation of specific name. The species epithet honors Eva B. Koppelhus, in order to recognize her contributions to vertebrate paleontology and palynology. Diagnosis. As for the genus. Referred specimen. TMP 74.10.31 (Fig. 4), a partial right dentary fragment. This is also from Dinosaur Provincial Park, and probably from the Dinosaur Park Formation, although the exact locality and stratigraphic position is unknown. Horizon and locality. Bonebed 55 (Fig. 2) in the Steveville region of Dinosaur Provincial Park, in middle of the Dinosaur Park Formation (Fig. 3), approximately 40 m above the contact with the Oldman Formation. Exact locality information is on record with the Royal Tyrrell Museum of Palaeontology.
Fig. 1. TMP 95.12.6, a partial left dentary, holotype of Unescoceratops koppelhusae, in A, medial, B, dorsal, and C, lateral views. Scale bar represents 10 cm.
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Fig. 2. Locality map for Unescoceratops and Gryphoceratops holotypes. TMP 95.12.6 was collected from bonebed 55 (BB55) located in the northwest corner of Dinosaur Provincial Park, in the pocket of badlands informally known as the Steveville badlands. ROM 56635 was collected from Black Coulee (formerly Deadhorse Coulee) approximately 10 km east of Writing-on-Stone Provincial Park and 50 km southeast of the village of Warner.
Key features and comparison. TMP 95.12.6 (Fig. 1) was described in Ryan and Currie (1998), and only features relevant to the present work will be reviewed here. TMP 95.12.6 is a nearly complete dentary lacking only the distal portion of the coronoid process and the posteriormost margin of the tooth row. The tooth row is curved in occlusal view and is complete with 15 alveoli. Replacement teeth are preserved in positions 2, 6, 7, 8, 9, and 11. The short, relatively deep dentary has a more moderately curved ventral border than seen in Cerasinops (MOR 300), Leptoceratops (CMN 8889), Prenoceratops (MNHCM [no number], Chinnery, 2004; fig. 7), Protoceratops (AMNH 6466), Udanoceratops tschizhovi Kurzanov 1992 (Kurzanov, 1992, fig. 1), or Zhuchengceratops inexpectus Xu et al. 2010 (ZCDM V0015), and differs from Montanoceratops (AMNH 5244), which has a relatively straight ventral margin (Fig. 5). Unescoceratops shares with Leptoceratops and Prenoceratops the development of a small flange at the anteroventral margin of the predentary-dentary symphysial surface, but, unlike these taxa, this flange projects well below the ventral margin of the dentary in Unescoceratops. The predentary symphysial contact surface is large and the contact for the ventral ramus of the predentary extends to at least the midlength of the dentary. The dentary of Unescoceratops is deeper anteriorly than it is posteriorly, and, together with the pronounced chin, gives the element a unique hatchet shape in lateral view. Only the proximal portion of the coronoid ramus is preserved, being broken where the head of the process begins. Although incomplete, it appears that the coronoid process is similar to Cerasinops in being inclined at a shallower posterodorsal angle
relative to the tooth row than other leptoceratopsids that have relatively vertical coronoid processes (Chinnery and Horner, 2007). It cannot be determined if Unescoceratops has the coronoid process notch (Chinnery, 2004) that is wide in Prenoceratops, but narrow in Leptoceratops, Montanoceratops and Udanoceratops. The presence of this notch is a synapomorphy of leptoceratopsids (Makovicky, 2010). It is also unknown if there is a large eminence (for insertion of an adductor slip) that lies just below the distal end of the coronoid process in Leptoceratops and Prenoceratops (Chinnery, 2004) and Zhuchengceratops (Xu et al., 2010). As in other leptoceratopsids, the Meckelian groove is dorsoventrally wide anteriorly but tapers posteriorly. The exact contact for the post-dentary bones cannot be determined for TMP 96.12.6, but based on the position of the posterior break, the contact for these elements was probably close to vertical as in Leptoceratops and Zhuchengceratops, and did not extend anteriorly as it does on Cerasinops. The dorsal margins of the dentary of Leptoceratops and Zhuchengceratops are similar in being strongly concave in lateral view with the anterior portion of the margin being considerably dorsal to the dentary tooth row. As noted by Xu et al. (2010), these features are variably developed in other leptoceratopsids. However, it is notably poorly developed in Unescoceratops which also lacks a prominent buccal crest on the dorsolateral edge of the dentary that obscures the tooth row in lateral view. Unescoceratops more closely resembles Prenoceratops than either Leptoceratops or Udanoceratops in having the anterodorsal pit for the predentary being at almost the same height of the tooth row rather than being positioned well above it. The posterior edge of the tooth row of
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Fig. 3. Occurrences of significant leptoceratopsid material in Alberta and northwestern Montana. Basal neoceratopsian teeth are known from microvertebrate localities ranging from the Milk River Formation to the Scollard Formation of Canada. It is uncertain whether the referred Montanoceratops braincase (AMNH 5244) was collected from the upper Horseshoe Canyon or the Scollard formation of central Alberta. Dinosaur Park biozones are discussed in the text. DMT ¼ Drumheller marine tongue. Modified from Brinkman (2003), Miyashita et al. (2010) and Sampson and Loewen (2010).
Unescoceratops must have extended almost to the posterior margin of the coronoid process as it does on Zhuchengceratops. Ryan and Currie (1998) noted that the unworn replacement teeth of TMP 95.12.6 (Fig. 1) are similar to those of Leptoceratops, but closer examination reveals a number of differences in the overall shape and extent of the cutting margin. In leptoceratopsids like Leptoceratops, the crowns of the dentary teeth have a greater height-to-width ratio with a straight mesial margin, whereas in
Unescoceratops, the height of the tooth is about equal to its width with sloping mesial and distal margins. This is associated with a difference in the length of the serrated margin of the tooth. In Leptoceratops, the cingulum extends further up the mesial and distal margins (more so on the former), separating the serrated margin of the tooth from its base. In Unescoceratops, the serrated margins of the tooth are strongly curved in lingual view and extend nearly to the base of the tooth. This means that at equivalent
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Holotype. ROM 56635, a partial right dentary (Fig. 6). Derivation of specific name. The species epithet honors Ian Morrison, in recognition of his expert preparation of the holotype jaw and his contributions to vertebrate paleontology while working for the Royal Ontario Museum. Diagnosis. As for genus. Horizon and locality. Black Coulee (formerly Deadhorse Coulee; Fig. 2), approximately 10 km east of Writing-on-Stone Provincial Park, Alberta, from the Deadhorse Coulee Member of the Milk River Formation (late Santonian). Detailed locality information is on record with the Royal Ontario Museum.
Fig. 4. Partial right dentary, TMP 74.10.31, in A, dorsal, and B, dorsolateral views. C, close-up of replacement tooth. Scale bar represents 1 cm.
positions in the tooth row, the crown of Leptoceratops appears more rectangular in lingual view than Unescoceratops, with the serrated cutting edge being restricted towards the distal half of the tooth. The dentary teeth of Unescoceratops are similar to Leptoceratops and most other leptoceratopsids in having a strong medial ridge on the lingual surface that thickens at its base and is confluent with the root. This ridge is offset distally and the bases of the mesial and distal lingual surfaces have narrow and wide shelves, or cingula, respectively. In well-preserved teeth near the middle portion of the dentary, two strong secondary longitudinal ridges are present on the distal surface and extend from the apex to almost the base of the tooth. The narrower tooth surface mesial to the ridge has a series of short ridges that run from the anterodorsal margin towards the mesoapical ridge at a steep angle. Not previously noted, the teeth of TMP 95.12.6 are enamelled on the lingual surfaces like other derived neoceratopsians. Gryphoceratops gen. nov. Type species. Gryphoceratops morrisoni gen. et. sp. nov. Derivation of generic name. Gryphon (mythological figure, Greek) þ ceratops (horned-face, Latinized Greek), referring to the legendary gryphon that had the body of a lion and the head of an eagle; a reference to the beaked-face. Diagnosis. Gryphoceratops is a small leptoceratopsid that can be differentiated from all other members of the clade in having the deepest dentary at midpoint relative to tooth row length, and a sigmoidally curved posterior margin of the predentary symphysial contact that terminates as a butt suture with a posterior margin that is almost perpendicular to the ventral dentary margin at the midpoint of the tooth row. Gryphoceratops shares with Leptoceratops, Prenoceratops and Unescoceratops the presence of the predentary flange. Gryphoceratops shares with Unescoceratops and Cerasinops the recumbent coronoid process, and shares with Unescoceratops the shape of the ventral dentary margin. Gryphoceratops morrisoni gen. et. sp. nov. Fig. 6
Description and comparison. The edentulous, partial right dentary, ROM 56635, has a total preserved length of 70 mm and an estimated total length of 90 mm. It is interpreted as representing an adult-sized animal based, in part, on the position of the posterior margin of the predentary contact surface on the ventrolateral margin. The height from the middle of the tooth row to the end of the predentary contact surface is 46 mm. The specimen is missing the anterior and posterior margins of the dentary ramus, and the distal and posterior margins of the coronoid process. Although the tooth row posteriorly is incomplete (57 mm, estimated), the preserved portion would have had at least ten alveoli, and the complete element could not have contained more than one additional alveolus at the end of the row. The tooth row is inset from the ramus and, as in Leptoceratops and Zhuchengceratops, the tooth row is strongly curved, which would have given the animal a short, blunt face. As in other leptoceratopsids, the lateral surface of the dentary bears a series of minute foramina distributed along a weakly demarcated lateral longitudinal ridge, which is continuous with the base of the coronoid process. Gryphoceratops is referred to Leptoceratopsidae based on its similarity to the dentaries of other leptoceratopsids, including the morphology of the dentary ramus and coronoid process, the symphysial articulation for the predentary, and the shape of the tooth row. It is similar to Leptoceratops, Prenoceratops and Unescoceratops in having a predentary symphysial contact developed as a small flange, and it appears to share with Unescoceratops the modification of this flange into a “chin”, although this cannot be confirmed. Although only a small portion of the ventral margin is preserved, it is complete enough to indicate that the dentary had a curved ventral margin as on all other leptoceratopsids except Montanoceratops, and resembles Unescoceratops in this feature. ROM 56635 shares with specimens of Cerasinops and Unescoceratops a recumbent coronoid process. It can be differentiated from Unescoceratops and all other leptoceratopsids in having a sigmoidally curved posterior margin of the predentary symphysial contact that terminates almost perpendicular to the ventral dentary margin ahead of the midline. Gryphoceratops also has a much shorter, deeper dentary ramus than all other leptoceratopsids. 3. Phylogenetic analysis To assess the systematic positions of Unescoceratops koppelhusae and Gryphoceratops morrisoni, the specimens were coded in the data matrix of Makovicky (2010), which was modified from the matrix of Makovicky and Norell (2006). We also added the codings for Koreaceratops from Lee et al. (2010) and Zhuchengceratops from Xu et al. (2010) following the conventions of Makovicky and Norell (2006) and Makovicky (2010), respectively.
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Fig. 5. Line diagrams of leptoceratopsids and selected out groups. Missing elements are listed in black and grey. Illustrations are based on the following material: Protoceratops andrewsi AMNH 6438 (modified from Brown and Schlaikjer, 1940); Montanoceratops cerorhynchus (modified from Chinnery and Weishampel, 1998); Cerasinops hodgskissi MOR 300 (modified from Chinnery and Horner, 2007); Prenoceratops pieganensis (MNHCM, no number); Udanoceratops tschizhovi PIN 3907/11 (modified from Kurzanov, 1992); Leptoceratops gracilis (CMN 8889); Zhuchengceratops inexpectus (ZCDM V0015); Unescoceratops koppelhusae (TMP 95.12.6). Gryphoceratops morrisoni (ROM 56635). Scale bar represents 10 cm.
Lee et al. (2010) added three addition characters to the Makovicky and Norell (2006) matrix and these were also added here in a slightly modified form (Table 1). Their characters 135 (the width of proximal end of the ungual relative to width of distal end of the preceding phalanx) and 136 (the height of the caudal neural spine is greater than the height of the chevron for any given caudal vertebra) become characters 148 and 149 in the matrix presented here. The codings for their new character 134 (the height ratio of middle caudal neural spine to associated centrum)
was used to recode the similar character 140 of the Makovicky (2010) matrix. We also added the new characters 150, development of anteroventral chin (absent ¼ 0, poorly developed ¼ 1, well-developed ¼ 2), and 151, inclination of the base (lower half) of the coronoid process (vertical ¼ 0; steeply inclined (>40%) ¼ 1). Finally, the separate codings used by Makovicky (2010) for the Montanoceratops specimens AMNH 5464, AMNH 5244, and MOR 542 were collapsed into one data line designated as Montanoceratops. Characters 72e83, 145, 146,
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Fig. 6. ROM 56635, a partial right dentary, holotype of Gryphoceratops morrisoni, in A, B, dorsal, C, D, medial, and E, F, lateral views. Scale bar represents 2 cm.
150 and 151 could be coded for the dentaries; 95e106 could be coded for the teeth. The final data matrix consisted of 151 characters scored for 26 ingroup taxa and two outgroup taxa, following Makovicky (2010). A cladistic analysis was performed using the branch-and-bound parsimony algorithm in PAUP*, 4.0b10 (Swofford, 2003) with all 151 characters equally weighted and run unordered. The analysis resulted in three most parsimonious trees (tree length ¼ 282 steps, CI ¼ 0.62, RI ¼ 0.77). The strict consensus tree is shown in Fig. 7,
along with Bootstrap values (1000 replicates) in order to describe the relative robustness of the topology. 4. Discussion 4.1. New leptoceratopsids Phylogenetic analysis supports the previous suggestions by Chinnery (2004), Makovicky and Norell (2006), Chinnery and
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Table 1 Data matrix for parsimony analyses of relationships between basal ceratopsian genera modified from Makovicky and Norell (2006). Characters 148 and 149 are the characters 135 and 136 of Lee et al. (2010). Character 140 is recoded as for character 134 of Lee et al. (2010). Characters 150 and 151 are new to this study. Hypsilophodon 00000???00 0000000000 001000000- 0000000000 0000?00011 00–000000 01?1000010 0000100010 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 00000-00000 Stegoceras 00000???00 0000000000 000011000- 0??010010? 0000000111 00–000000 0?00000?00 ?000100100 000000?000 0000000000 000000??0? 0?10?????0 0?0?0???01 00011?-0?0?0000-?0000 Archaeoceratops 1100101111 011010000? ?010001110 01?110??01 1??????11? ?10???1110 1?01001110 1?101010?? 01?11100?1 0101000101 ???0?1000? ?0100?0??? ???????00? ?000001100000?0-00000 Asiaceratops ????1???1? ????1?0??? ?01??????? ?????????? ?????????? ??????11?0 0????????? ?1101??0?? ????01???? ??3-000?00 0?001????? ?????1???? 1????????? ??0??0??0? ??????????? Bagaceratops 11001?1111 01?01?01?0 1010001111 0101010112 1100?111?? ??11101110 1001001111 111110?011 011111?111 013-000201 010011???? 1????????? ??????0??? ???0000103001?0-?1100 Chaoyangsaurus 110110001? ?00?120??? ?0?1??010? ????0????0 ????00001? ??????01?0 ???????110 0?101001?? 00000000?1 1110000000 0000000000 00???????? ?????????? ???110??0?????0-0??00 Centrosaurus 1110101111 0110011211 1000112111 1102110111 1211111100 2211?12110 1110112110 211110?010 121011000? 013-111201 1101111112 1203101110 1011111111 1110000100 00010-11000 Leptoceratops 1100111111 0110120000 1110001110 0110001101 100??111?1 01000011?1 0011010111 1210001010 0110110101 013-002211 0110110101 1101011101 1000000000 0000000100 00011000110 Graciliceratops 1100?????? ?????????0 ??????1??? ?????10111 1????????? ???100?1?? ?????????? ??1?1??0?? 01?111???1 ????000201 0100?????? ??1??1???1 ??????0??0 000000?10? 00000-?1?0? Montanoceratops 1????????1 ????1????0 10100?1?10 011??011?1 1????????? 0?0???1121 00?1010?1? ??1?101010 0111110??1 013?002211 0110?10111 ?112011101 10?0000000 000?00?102 11??1100100 Protoceratops 1100111111 0100120100 1010001111 0101010112 110011111? 1211{01}01110 1001001111 1111001011 0111110111 0111000201 0100110111 1112011101 1000010000 001000?102 00000-11100 Psit. mongoliensis 1101100011 1011220001 100100110? 0000000000 0010001111 0100100100 0001001000 0110-1000? 01?0000001 003-000000 0000000000 1000000001 1100000000 0000010110 00000-00000 Triceratops 1110111111 0010011211 1000112111 1102110111 1211111100 2210112110 1110112110 211110?010 1210110001 013-111201 11011?1112 1203101110 1011111111 1110000101 00010-11?00 Udanoceratops 1??0111111 ?0??1?00?0 ?1????1110 ?????????1 1????????? ?????????? ????????1? ?21?0??0?0 01?011??01 013-002211 011011???? ??02011??1 100??????0 ????000101 ??01???1100 Zuniceratops ???????1?? ???????0?? ?0????1??? 1????????? ?????????? ???????1?? ?????????? ?11?1??0?? 0????????? ???-0?1201 01?01????? ?????0???? ????????1? ???0?00??0 ?01?0-???00 Liaoceratops ?100101111 1010100000 101100100- 0101001100 1?00000111 0101100110 10?10011?0 0110011000 01?0101001 0100000100 ?10001???? ?????????? ?0???????? ???000110?000?0-???00 Psit. sinensis 1101110011 101122000? ?00000110- 0000000000 0?00????1? 010010???? ???0???000 01101000?? 01?000000? ?03-00?0?0 00?000??00 10?1000??? ?10??????0 ?0000101100?000-?0000 Xuanhuaceratops ?????????? ??0??????? ?????????? ?????????? ?????????? ?????????? ?????????? ?11010?1?? ???0?000?1 111?000000 00000000?? ??0??????1 10???????0 ?0?110???? ?????-0??0? Yamaceratops 11??1010?? ??1??????0 1010001010 0101001101 1100000111 010???1110 10?100111? 11101010?0 01111110?1 01{01}0000100 010011???? ??0??1???? ?????????? ?00000?10? 00??0-0??00 Prenoceratops ??0?1???1? 00101?000? ?0100?1110 011??011?1 1????????? ??0???1121 0??????11? 12100010?? 011011???1 013-002211 0110?1???? ?????????? ?????????? ???0?00?00 00001000110 Cerasinops 1????????? ?????????? ?0????10?? 01???011?1 1????????? 1101001111 00?1010??? ??1?0????? 0{12}1111???1 ?11?00210? 0?1????0?1 101{12}?1?1?1 100?????10 00000??10? 00??0-00?01
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Table 1 (continued). Yinlong 01001000?0 ?0?001000? ?00001000- 0100000000 0000?00?1? 00–110020 0??00?1010 01000000?0 0000000101 ?100000000 0000?0000? ?0??00?0?? ???00100?0 ??01101110000?0-?0000 Koreaceratops ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????101?? ????????0? ?00??????3 ???????01?? Zhuchengceratops 1????????? ?????????? ?1???1???? ?????????? ???1111111 ?????????? ????????10 ??11000010 11100001?1 01???02211 011011???? 010??????? ?????????? ????0???0? ????101??00 Unescoceratops ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?2100000?? 11???????? ????00?2?1 0110?1???? ?????????? ?????????? ?????????? ?????????21 Gryphoceratops ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????????? ?????000?? ?????????? ????00???? 0??0?????? ?????????? ?????????? ?????????? ??????????1
Horner (2007), and Makovicky (2010) that Unescoceratops, based on TMP 95.12.1, cannot be referred to any previously known nonceratopsid taxon, and positions Unescoceratops as the sister taxon to the recently described Zhuchengceratops (Xu et al., 2010) from the Upper Cretaceous Wangshi Group of Shandong Province, China. Although support for this relationship is relatively weak, this analysis does have a CI value (0.62 vs. 0.63) similar to the recent analysis published by Xu et al. (2010). The analysis confirms that Unescoceratops and Gryphoceratops are deeply nested within Leptoceratopsidae, sharing with them the deep lower jaw with a curved ventral margin (Leptoceratopsidae includes taxa closer to Leptoceratops gracilis than to Triceratops horridus; Makovicky, 2001). Gryphoceratops does appear to share with the holotype specimen of U. koppelhusae the presence of a “chin” (character150), and possibly
the gentle slope of the posterior portion of the ventral margin of the dentary, but these characters have been coded as “?” in this analysis. Despite this, this analysis indicates that Gryphoceratops is the sister taxon to Unescoceratops, albeit with weak bootstrap support. This analysis also removes Zhuchengceratops from a trichotomy with Leptoceratops and Udanoceratops recovered in the analysis by Xu et al. (2010). In all other respects, the topology of the consensus tree is consistent with the consensus tree published by Makovicky (2010). Unescoceratops koppelhusae can be differentiated from all other leptoceratopsids on the basis of three autapomorphies: the gently, rather than steeply, sloping posterior portion of the ventral margin of the dentary; the presence of a prominent, chin-like flange projecting below the ventral margin; and dentary teeth from the
Fig. 7. Suggested systematic position of Unescoceratops koppelhusae and Gryphoceratops morrisoni among the Ceratopsia. Bootstrap values are labelled beside node points.
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midpoint of the tooth row with rounded profiles. Makovicky (2010) identified a “chin” on Montanoceratops. However, this feature is absent on the referred specimen MOR 542, and the chin on the holotype AMNH 5464 appears to be a thickening of the anteroventral margin of the dentary rather than a distinct flange-like chin. Leptoceratops and Prenoceratops both share the presence of a distinct flange demarcating the anteroventral corner of the predentary-dentary symphysial surface. However, this flange does not develop into a distinct chin-like flange that projects below the ventral margin of the dentary as it does in U. koppelhusae. The holotype jaw of Unescoceratops koppelhusae (TMP 95.12.6) has the same number of alveoli (15) as the holotype (ZCDM V0015) of Zhuchengceratops, and is similarly thin transversely. Xu et al. (2010) inferred that their specimen probably represents an adult individual slightly larger than an adult-sized Leptoceratops (approximately 2 m: Brown, 1914; Sternberg, 1951; Russell, 1970) based on the complete closure of the neurocentral sutures of all preserved presacral vertebrae. However, the length of TMP 95.12.6 (174 mm) is less than half the length of the dentary of ZCDM V0015, suggesting that Unescoceratops reached maturity at a smaller body length (
