New leptoceratopsids from the Upper Cretaceous of Alberta, Canada
Highlights
► Two new leptoceratopsids are described from the Campanian and Santonian of Alberta. ► The Campanian taxon has a unique dentary tooth shape not shared by other leptoceratopsids. ► The Santonian taxon represents the oldest known leptoceratopsid (∼83 Ma). ► The Santonian taxon represents the smallest adult-sized ceratopsian from North America.
Introduction
In 1998, Ryan and Currie reported on the first recorded non-ceratopsid 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 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 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.
Section snippets
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.
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. Lee et al. (2010) added three addition characters to the Makovicky
New leptoceratopsids
Phylogenetic analysis supports the previous suggestions by Chinnery, 2004, Makovicky and Norell, 2006, Chinnery and Horner, 2007, and Makovicky (2010) that Unescoceratops, based on TMP 95.12.1, cannot be referred to any previously known non-ceratopsid 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,
Acknowledgements
We thank Denis Braman and David Eberth for information on the stratigraphy of Alberta and Montana. Liz Freedman and Brenda Chinnery-Allgeier provided specimen photographs, and Ian Morrison did an excellent job preparing ROM 56635. Comments by two anonymous reviewers and the handling editor improved the manuscript. Any errors are, of course, our own.
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