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A New Centrosaurine Ceratopsid from the Oldman Formation of Alberta and Its Implications for Centrosaurine Taxonomy and Systematics

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A New Centrosaurine Ceratopsid from the Oldman Formation of Alberta and Its Implications for Centrosaurine Taxonomy and Systematics University of Calgary PRISM: University of Calgary's Digital Repository Science Science Research & Publications 2005 A new centrosaurine ceratopsid from the Oldman Formation of Alberta and its implications for centrosaurine taxonomy and systematics Ryan, Michael J.; Russell, Anthony P. National Research Council Canada Ryan, M.J. and A.P. Russell. (2005). A new centrosaurine ceratopsid from the Oldman Formation of Alberta and its implications for centrosaurine taxonomy and systematics. Can. J. Earth Sciences 42: 1369-1387. http://hdl.handle.net/1880/47001 journal article Downloaded from PRISM: https://prism.ucalgary.ca 1369 A new centrosaurine ceratopsid from the Oldman Formation of Alberta and its implications for centrosaurine taxonomy and systematics Michael J. Ryan and Anthony P. Russell Abstract: Centrosaurus brinkmani (sp. nov) is distinguished from Centrosaurus apertus by key features of its cranial ornamentation, including the shape and orientation of the postorbital horn and parietal ornamentation at parietal locus 3, the shape of the parietal ornamentation at locus 2, and the possession of accessory parietal ossifications developed as short spines on the caudal parietal ramus. This species is restricted to the Oldman Formation of southern Alberta and is the oldest ceratopsid represented by diagnostic material in Canada. Phylogenetic analysis of the Centrosaurinae suggests that the development of spike-like ornamentation at the parietal locus 3 parietal locus is inversely related to the development of the P1 parietal ornamentation. Résumé : Centrosaurus brinkmani (sp. nov) se distingue de Centrosaurus apertus par d’importants caractères de son ornementation crânienne dont la forme et l’orientation de la corne post-orbitale et de l’ornementation pariétale au locus pariétal no 3, la forme de l’ornementation pariétale au locus no 2 et la présence d’ossifications pariétales accessoires formant de courtes épines sur la rame caudale pariétale. La présence de cette espèce se limite à la Formation d’Oldman du sud de l’Alberta et il s’agit du plus ancien Cératopsidé représenté par du matériel diagnostique au Canada. L’analyse phylogénique des Centrosaurinés indique qu’il existe une relation inverse entre le développement de l’ornementation en forme de pointe au locus pariétal no 3 et le développement de l’ornementation au locus pariétal no 1. [Traduit par la Rédaction] Ryan and Russell 1387 Introduction Group. The centrosaurines Centrosaurus apertus and Styraco- saurus albertensis are commonly recovered from the Dinosaur The late Campanian Judith River Group (Fig. 1) of Alberta Park Formation, where they also appear to be stratigraphically has yielded over three dozen dinosaur taxa (Ryan and Russell restricted to the lower and upper part of the formation, 2001). Most have been recovered from the Dinosaur Park respectively (Ryan et al. 2001; Ryan and Evans 2005). Formation (notably from Dinosaur Provincial Park), where Diagnostic ceratopsid material is rare in the Oldman For- isolated elements, partial and complete skeletons, and bone mation and collected material has previously included only beds are commonly encountered. The underlying Oldman indeterminate centrosaurine specimens (Ryan and Russell Formation has numerically fewer recognized taxa, partly 2001). One specimen of C. apertus (an almost complete because of the relative lack of exposure compared with the skull, TMP 93.70.1) is known from the extreme southern Dinosaur Park Formation. Bone beds and skeletons are found part of the province, but it occurs in sediments that are less frequently in the Oldman Formation and, when they are equivalent in time to the lower part of the Dinosaur Park encountered, diagnostic material is not always present (Ryan Formation in Dinosaur Provincial Park (Eberth and Hamblin and Russell 2001). 1993). Chasmosaurine specimens previously reported from Among the ceratopsids recovered from the Judith River the Oldman Formation (e.g., Anchiceratops, Langston, Jr. Group are the chasmosaurines Chasmosaurus belli, C. irvinensis, 1959) actually occur in sediments now recognized as be- and C. russelli, which appear to be stratigraphically partitioned longing to the Dinosaur Park Formation (and are equivalent within the Dinosaur Park Formation (Holmes et al. 2001). to the uppermost sediments of this formation in Dinosaur The genus is not known from the Oldman Formation, and no Provincial Park). chasmosaurine bone beds are known from the Judith River Excavations of two new paucispecific centrosaurine bone beds in the Oldman Formation of Alberta by the Field Experi- Received 17 August 2004. Accepted 15 February 2005. ence Program of the Royal Tyrrell Museum of Palaeontology Published on the NRC Research Press Web site at have yielded hundreds of disarticulated and mostly fragmen- http://cjes.nrc.ca on 4 November 2005. tary specimens that represent a new species of Centrosaurus distinguished by characters of its supraorbital and parietal Paper handled by Associate Editor H.-D. Sues. ornamentation. M.J. Ryan,1,2 andA.P. Russell. University of Calgary, 2500 In one quarry in bone bed (BB) 138 (Fig. 2) in Dinosaur University Dr. NW, Calgary, AB T2N 1B4, Canada. Provincial Park, 27 juxtaposing 1-m grids were completely 1Corresponding author (e-mail: [email protected]). excavated between 1996 and 2000 and yielded 1042 elements. 2Present address: Cleveland Museum of Natural History, 1 The material was recovered from a fine-grained sandstone Wade Oval Dr., University Circle, Cleveland, OH 44106, USA. and, although much of the material is fragmentary because Can. J. Earth Sci. 42: 1369–1387 (2005) doi: 10.1139/E05-029 © 2005 NRC Canada 1370 Can. J. Earth Sci. Vol. 42, 2005 Fig. 1. Temporal distribution of late Campanian centrosaurines in Fig. 2. Locality map for bone bed 138 and the Milk River Ridge the Dinosaur Provincial Park region of southern Alberta. Grey reservoir bone bed, southern Alberta. BB, bone bed. bars indicate regional coal zones. Radiometric dates (in Ma) are taken from (a) Lerbekmo and Braman (2002), (b, c) Eberth and Braman (1993), and (d) Goodwin and Deino (1989). Stippling indicates marine shales. The figure incorporates palaeomagnetostratigraphic data from Braman et al. (1995) and Lerbekmo and Braman (2002). FM, Formation; GP, Group. of pre-depositional processes, it is well preserved and undis- torted. Of the 750 elements that could be identified to taxa, 689 (92%) are ceratopsid and are referred to the new taxon. The Milk River Ridge reservoir bone bed (MRR BB) in southern Alberta (Fig. 2) is unusual in that the bone-yielding substratum extends for approximately 50 m along the shoreline Systematic paleontology of a man-made reservoir. Exposure of the bone bed is partially dependant upon the water level in the reservoir. As a conse- Ornithischia Seeley, 1888 quence of the MRR BB being located within the fluctuating Ceratopsia Marsh, 1890 water table of the reservoir, many of the elements recovered Neoceratopsia Sereno, 1986 are broken owing to modern frost heave and the resulting Ceratopsidae Marsh, 1888 cracks are infilled with precipitated calcite. In 1998, 370 Centrosuarinae Lambe, 1915 elements were collected from 12 completely excavated, 1-m Genus Centrosaurssus Lambe, 1904 grids from two quarries excavated along the reservoir margin. DIAGNOSIS: After Dodson (1990, p. 234): “those species found Of the 222 elements that could be identified to taxa (at least in Alberta that have the thickened caudal parietal margin to the level of family), 206 (93%) are ceratopsid and are with hook-like processes projecting caudally and hornlike referred to the new taxon. processes projecting rostrally.” AMENDED DIAGNOSIS: Centrosaurine ceratopsid with parietal Institutional abbreviations process 1 (P1) (see Sampson et al. 1997 and Ryan et al. ANSP, The Academy of Natural Sciences, Philadelphia, 2001 for numbering of parietal processes) developed as a Pennsylvania, USA.; CMN, Canadian Museum of Nature, large procurving hook (one of the pair may rarely be absent Ottawa, Ontario, Canada; UCMP, Museum of Paleontology, from either side, e.g., CMN 971). Unlike all valid centro- University of California, Berkeley, California, USA.; MOR, saurines, except Styracosaurus, the nasal horn core is erect, Museum of the Rockies, Montana State University, Bozeman, elongate, and laterally compressed with the apex dorsally Montana, USA.; NAMAL, North American Museum of oriented or inflected rostrally. Unmodified adult supraorbital Ancient Life, Thanksgiving Point, Utah; RSM, Royal Sas- horn cores have an inflated pyramidal shape with rounded katchewan Museum, Regina, Saskatchewan, Canada; TMP, apices. Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada. TYPE SPECIES: Centrosaurus apertus Lambe, 1904 © 2005 NRC Canada Ryan and Russell 1371 AMENDED SPECIFIC DIAGNOSIS FOR CENTROSAURUS APERTUS: Parietal TYPE LOCALITY: Bone bed 138 (Fig. 2), Dinosaur Provincial P2 processes developed and medially curled as hooks, in the Park, approximately 50 km from Brooks, Alberta, Canada plane of the frill, from the posterior parietal ramus on either (12 463090E, 5621680N (WGS 84)), Oldman Formation, side of the midline parietal bar. Similarly, developed hooks 14.6 m below the contact with the Dinosaur Park Formation on S. albertensis are never as robust. Parietal process 3 (645 m above sea level). The MRR BB (Fig. 2) near Warner, unmodified from a small, depressed, crescent-shaped epoc- Alberta, approximately 180 km southwest of BB 138, is also cipital. Unlike all centrosaurines,
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