Albertosaurus libratus
Creators: name: Carr, T. D.
Publisher: name: Zenodo
Year: 1999
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Dinosauria
Tyrannosauridae
Albertosaurus
Albertosaurus libratus

description: The holotype of A. libratus (CMN 2120) was first named Gorgosaurus libratus by Lambe (1914). Its slender upper incisiform teeth distinguished it from the robust dentition of Deinodon horridus Leidy, 1856 from the equivalent Judith River Formation of Montana. Later, Matthew and Brown (1922) showed that the type teeth of Deinodon and Gorgosaurus were indistinguishable, and that the two taxa likely were congeneric. However, the authors retained generic distinction in the absence of diagnostic skeletal material for Deinodon. Russell (1970), in agreement with Gilmore (1946), determined that the lectotype of D. horridus, comprising two incomplete incisiform teeth, is indistinguishable from the Dinosaur Park material, and D. horridus is therefore a nomen dubium (for an opposing view, see Sahni, 1972). Russell (1970) concluded that Gorgosaurus libratus and Albertosaurus sarcophagus Osborn, 1905 were congeneric on the basis of overall similarity, a position that is upheld herein on a phylogenetic systematic basis (see Carr, 1996). Albertosaurus was rediagnosed and distinguished from Daspletosaurus by Russell (1970). I agree with Russell (1970) that the types and referred material of G. libratus and A. sarcophagus appear to be identical, and are different from specimens referred to Tyrannosaurus bataar Maleev, 1955b and T. rex Osborn, 1905. I also agree with Carpenter (1992) that discrete differences exist between the tyrannosaurid skulls from the Dinosaur Park and Horseshoe Canyon formations. Ontogenetic changes to discrete morphological characters are based on specimens referred to A. libratus, with the exception of FMNH PR308. Morphologically, this specimen is identical to the morphotype represented by D. torosus. Although the skull is considered representative of A. libratus (Russell, 1970: fig. 1; Paul, 1988:335; Carpenter, 1992: figs. 1, 2E), the specimen is less complete (Fig. 1A, B) than usually shown. Also, FMNH PR308 has been focal in discussions of tyrannosaurid diversity, with specific reference to tooth size and number (Bakker et al., 1988; Paul, 1988). In fact, every upper tooth and all but 13 dentary teeth are restored in plaster (pers. obs.), rendering the material basis of the former aspect moot. The relationship between size and morphology has not been adequately studied in large theropods, and no attempt has been made to do so herein. This important question would best be answered by a quantitative and comparative study in the realms of biomechanics and functional morphology. The ontogenetic characters in this study were chosen cognizant of this issue. Thus, inclusive features of possible structural importance to the skull were avoided.
description: Published as part of <i>Carr, T. D., 1999, Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria), pp. 497-520 in Journal of Vertebrate Paleontology 19 (3)</i> on pages 498-499, DOI: 10.1080/02724634.1999.10011161, http://zenodo.org/record/3372241
description: {"references": ["Lambe, L. M. 1914. On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of Stephanosaurus marginatus from the same horizon. The Ottawa Naturalist 28: 158 - 164.", "Leidy, J. 1856. Notice of remains of extinct reptiles and fishes, discovered by Dr. F. V. Hayden in the badlands of the Judith River, Nebraska Territory. Proceedings of the Academy of Natural Sciences of Philadelphia 8: 72 - 73.", "Matthew, W. D., and B. Brown. 1922. The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta. Bulletin of the American Museum of Natural History 46: 367 - 385.", "Russell, D. A. 1970. Tyrannosaurs From the Late Cretaceous of Western Canada. National Museum of Natural Sciences Publications in Palaeontology 1: 1 - 30.", "Gilmore, C. W. 1946. A new carnivorous dinosaur from the Lance Formation of Montana. Smithsonian Miscellaneous Collections 106: 1 - 19.", "Sahni, A. 1972. The vertebrate fauna of the Judith River Formation, Montana. Bulletin of the American Museum of Natural History 147: 232 - 412.", "Osborn, H. F. 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the American Museum of Natural History 21: 259 - 265.", "Carr, T. D. 1996. Cranial osteology and craniofacial ontogeny in Tyrannosauridae (Dinosauria: Theropoda) from the Dinosaur Park Formation (Judith River Group, Upper Cretaceous: Campanian) of Alberta. M. Sc. thesis, University of Toronto, 358 pp.", "--------- 1955 b. [A giant meat-eating dinosaur from Mongolia.] Doklady Akademii Nauk SSSR 104: 634 - 637. [Russian.]", "Carpenter, K. 1992. Tyrannosaurids (Dinosauria) of Asia and North America; pp. 250 - 268 in N. Mateer and P. J. Chen (eds.), Aspects of Nonmarine Cretaceous Geology. China Ocean Press, Beijing", "Paul, G. S. 1988. Predatory Dinosaurs of the World: A Complete Illustrated Guide. Simon and Schuster, New York, 464 pp", "Bakker, R. T., M. Williams, and P. J. Currie. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 1 - 30."]}