Browsing by Author "Currie, Philip J."
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- ItemOpen AccessBones and tracks at Wally's Beach Site (DhPg8): an investigation of the latest Pleistocene mega-fauna of southern Alberta(2009) McNeil, Paul E.; Hills, Leonard V.; Currie, Philip J.Wally's Beach (DhPg-8) is a latest Pleistocene palaeontological/archaeological site in southern Alberta, Canada. A ten metre water level drop of the St. Mary Reservoir exposed the reservoir floor to intense wind erosion, exposing a diverse assemblage of mammal bones, tracks, trackways, tramplegrounds, and Palaeo-Indian artifacts. This site provides a rare look at the latest Pleistocene mega-fauna of southern Alberta. Pleistocene tracks are rare worldwide, and Wally's Beach documents the only Canadian locality. Six new ichnospecies are defined that include tracks of extinct wooly mammoth (Mammuthus primigenius), western camel (Came/ops hesternus), Mexican horse (Equus conversidens), ancient bison (Bison antiquus), and extant caribou (Rangifer tarandus). Analysis of the tracks provides information on the biomechanics of locomotion and behaviour. Mammoth track data indicate a walking speed of four to five km/h for adult wooly mammoths. The behaviour of Pleistocene mammals, as revealed through tracks and tramplegrounds, is similar to that exhibited by their extant relatives, despite a long period since they shared a common ancestor. This indicates that extrapolating the behaviour of fossil animals from that of their modem relatives is valid. Mammoth tramplegrounds confirm previous Wally's Beach track studies that showed a deficit of juveniles, suggesting that Late Pleistocene mammoth populations in southern Alberta were in decline. Multigeneric trample grounds, formed in a short period of time, suggest high concentrations of mammals simultaneously inhabited the Pleistocene Albertan steppe. Wally's Beach horse bones provide new insights into human horse utilization, characteristics for identification, and Late Pleistocene relationships. Equus conversidens and E. lambei populations may be separated based on both qualitative characteristics and by quantitative methods. The humeri of E. conversidens are slightly longer on average than those of E. lambei. Quantitative analysis demonstrated that the Wally's Beach horses and the Yukon horses may be separated based on skull measurements. This method of separation could be useful for localities that are interpreted to have many horse species. Equus conversidens has a broader, boxier posterior skull and a relatively longer and narrower snout than E. lambei.
- ItemOpen AccessCraniocervical functional morphology of several North American coelurosaurian dinosaurs(2006) Samman, Tanya; Hills, Leonard V.; Currie, Philip J.
- ItemOpen AccessDescription and phylogenetic implications of extant and fossil oologic remains(2004) Zelenitsky, Darla K.; Currie, Philip J.Rigorous analytical techniques are combined with phylogeneticsystematic methodology to provide a new perspective on the scientific informativeness of the eggs and eggshells of both extant and extinct dinosaurs. Re-description of the eggs of paleognathous birds reveals that numerous eggshell characteristics were overlooked by previous investigators. A cladistic analysis of discrete egg characters of paleognaths reveals that although trees based on egg data provide less resolution among taxa than those based on skeletal data, egg data do provide phylogenetic information and can help resolve disagreements in relationships derived from skeletal data. In an analysis based on the egg data alone, tinamous are basal among paleognaths, Apteryx is basal among ratites and the sister taxon of an unresolved clade consisting of large ratites, within which Aepyornis and dinornithids form a subclade and Casuarius and Dromaius form a subclade. When the egg data are combined with the skeletal data of Bledsoe (1988), the clade of Apteryx, Casuarius, and Dromaius is dissolved, and Apteryx moves to a basal position within Ratitae. Analysis of 13 absolute measurements and ratios from the eggs reveals that only 4 of these continuous characters are suitable for cladistic analysis. A cladistic analysis of the continuous and discrete characters provides further resolution among taxa within the tree based on egg data in that Struthio and Rhea form a clade. Fossil eggs of several dinosaurs (including birds) are described and included in a cladistic analysis of 24 ootaxa, the results of which, in general, are comparable to those drawn from skeletal-based studies. Sauropod eggs are basal in Saurischia, allosauroid eggs are basal in Theropoda, the eggs of oviraptorids and dromaeosaurids form a derived clade, and the eggs of troodontids and birds form a clade. Unexpected results include the basal position of therizinosaurid eggs, a clade consisting of Protoceratopsidovum (Protoceratops eggs) and troodontid eggs, and a clade consisting of Deinonychus and oviraptorid eggs. These anomalies may call the alleged parentage of these eggs into question. The evolutionary-systematic method that was used to construct the traditional parataxonomic system for fossil eggs is eschewed, and a new nomenclatural system employing a phylogenetic-systematic methodology is proposed. Phylogenetic definitions are erected for seven ooclades of Saurischia, following the tenets of phylogenetic nomenclature.
- ItemOpen AccessTwo exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids(Journal of Vertebrate Paleontology (Taylor and Francis), 0022-04-13) Voris, Jared. T.; Zelenitsky, Darla K.; Therrien, Francois; Ridgely, Ryan C.; Currie, Philip J.; Witmer, Lawrence, M.Known from dozens of specimens discovered since the early 20th century, Gorgosaurus libratus has arguably contributed more than any other taxon to our understanding of the life history of tyrannosaurids. However, juvenile material for this taxon is rare. Here, we describe two small, articulated Gorgosaurus specimens (skull lengths of ca. 500 mm) that help advance our knowledge of the anatomy and ontogeny of this taxon and of tyrannosaurids in general. The new specimens exhibit hallmark juvenile tyrannosaurid features, including long, low, and narrow skulls, large circular orbits, absent or incipient cranial ornamentation, ziphodont dentition, and an overall gracile skull frame. Comparison with other Gorgosaurus specimens of various ontogenetic stages allows for an examination of the timing of morphological changes that occurred through ontogeny in this taxon relative to other tyrannosaurids. Of particular note, Gorgosaurus and the larger Tyrannosaurus rex are found to have experienced similar ontogenetic transformations at similar percent skull length relative to the large known individuals for each respective taxon but at different absolute body sizes and biological ages, occurring at a larger size and older age in Tyrannosaurus than in Gorgosaurus. These results suggest a dissociation between the timing of cranial development and body size in tyrannosaurids. Finally, the recognition of ontogenetically invariant characters in Gorgosaurus makes it possible to determine the taxonomic identity of previously misidentified specimens.