Tyrannosaurus bataar Osborn 1905
Creators: name: Carpenter, K.
Publisher: name: Zenodo
Year: 1992
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Dinosauria
Tyrannosauridae
Tyrannosaurus
Tyrannosaurus bataar

description: <i>Tyrannosaurus</i> bataarMaleev 1995a Figs. 2B, 4, 5B <i>= Tarbosaurus efremovi Maleev 1955b</i> <i>= Gorgosaurus lancinator Maleev 1955b</i> <i>= Tarbosaurus bataar (Maleev) 1955 b</i> <b>Holotype:</b> PIN 551-1 partial skull from the Nemegt Formation, Mongolian People’s Republic. <b>Diagnosis:</b> Angular terminates anterior to the surangular fenestra;surangular fenestra proportionally smaller than in <i>Tyrannosaurus rex</i>; surangular fenestra proportionally smaller than in <i>T. rex.</i> <b>Stratigraphic and Paleobiogeographic Distribution:</b> Nemegt Formation and Upper White Beds of Khermeen Tsav, Mongolian People’s Republic; possibly <i>the</i> Subashi Formation,Xinjiang,People’s Republic of China. <b>Discussion:</b> Maleev (1955a,b; 1974) recognized three genera and four species of tyrannosaurids from Mongolia: <i>Tyrannosaurus bataar, Tarbosaurus efremovi, Gorgosaurus lancinator</i> and <i>Gorgosaurus novojilovi.</i> Rozhdestvensky (1965),however,argued that most of the differences cited by Maleev were ontogenetic, and that only a single species was represented. Rozhdestvensky also argued that this single species was intermediate between <i>Albertosaurus</i> and <i>Tyrannosaurus</i> and, thus, represented a distinct genus for which the name <i>Tarbosaurus</i> was available. Accordingly, Rozhdestvensky referred all Mongolian tyrannosaurid to <i>Tarbosaurus bataar.</i> Re-examination of Maleev’s figures (Maleev, 1955a, 1955 <i>b</i>; 1974),as well as photographs of these specimens and of those collected by the Polish palaeontological expeditions to Mongolia, reveal that Rozhdestvensky erred in a number of points in his analysis. The quadratojugal process of the jugal in <i>T. bataar</i> reaches the posterior rim of the lateral temporal fenestra <i>as it</i> does in <i>T. rex. The</i> tetragonal-shaped <i>ascending</i> process of the jugal in <i>T. rex</i>,this observation is based on AMNH 5027 (Osborn, 1912). A new skull of <i>T. rex</i>, LACM 23844,has a tapering ascending process as in PIN 551-3, thus showing the shape of this bone is variable. Development of the ascending process into the orbit is variable as indicated by the holotype <i>T. bataar</i>, PIN 551-1, which shows a slight development of the jugal within the orbint. This makes it intermediate in shape between AMNH 5027 and PIN 551-3. Another taxonomical difference Rozhdestvensky stated was the smaller size of the Mongolian tyrannosaurid. However,the holotype <i>skull</i>, PIN 551-1,has premaxillary to occipital condyle length of 1220 mm (Maleev, 1955a, 1974). This compares to 1210 mm for AMNH 5027, <i>T. rex</i> (Osborn, 1912). Thus,contrary to Rozhdestvensky’s(1965) <i>claims</i>, <i>T. bataar</i> is not intermediate between <i>Albertosaurus</i> and <i>Tyrannosaurus</i>, but is generically indistinguishable from <i>Tyrannosaurus.</i> It is remarkable that of the five skulls of <i>T. rex</i> known all are adults (however see below). This is not the case with <i>T. bataar.</i> Figure 4 shows a growth series of skulls from the smallest with a premaxillary-occipital condyle length of 825 mm to the largest with a premaxillary-occipital condyle length of 1220mm. The general ontogenetic trend is a deepening of the skull, shortening of the muzzle,and an increase in the rugosity of the region dorsal to the orbit. As may be seen, the smaller skulls resemble that of Albertosaurus (compare Figs. 4 C, <b>D</b> with Fig. 2 E),especially because of the longer muzzle. <i>Thus</i>,it is understandable that Maleev referred these skulls to <i>Gorgosaurus</i> (<i>= Albertosaurus).</i> However,the well-developed stereoscopic <i>vision</i> (due to the differentiation of the muzzle from the cranium) separates these skulls from Albertosaurus. Variation in the skulls is apparent in the posterior portion of the lateral temporal fenestra where the squamosal may butt against the quadratojugal (Fig. 4 B and D) or there may be an overlap (Fig. 4 C). A similar pattern is seen in <i>T. rex</i> as well (Carpenter,in press). There has been some confusion about the astragulus in <i>Tyrannosaurus.</i> Welles and Long (1974) figured an element associated with AMNH 5827 that they ascribed as a <i>Tyrannosaurus</i> astragulus. This element, however, is unlike any theropod astragulus <i>known</i>,and is certainly very different from the astragulus associated with MOR 009, <i>Tyrannosaurus rex.</i> This astragulus resembles that of <i>Albertosaurus</i> as would be expected. Comparison of the original drawings by Christman of the element figured by Welles and Long show that it is,in fact,a medial and dorsal view of the right quadrate of AMNH 5027 (Fig. 3). At this time the specific differences between the postcrania of <i>T. rew</i> and <i>T, bataar</i> have not been established. This is due to the considerable amount of variation among the <i>T. rex</i> specimens (Carpenter,in press). Some of the differences may be individual, but most appear to be sexual. Until the range of this variation can be determined, it is not certain what postcranial characters separate <i>T. rex</i> from <i>T. bataar.</i> With regard to the maxilla from the Tornillo Formation of Texas ascribed by Lawson (1976) to <i>T.</i> rex,it does not belong to <i>Tyrannosaurus</i> (Carpenter,in press), but another short-faced theropod. A description of the postcrania of <i>Tyrannosaurus</i> is in preparation.
description: Published as part of <i>Carpenter, K., 1992, Tyrannosaurids (Dinosauria) of Asia and North America, pp. 250-268 in Aspects of Nonmarine Cretaceous Geology, Beijing :China Ocean Press</i> on pages 254-256, DOI: 10.5281/zenodo.1038212
description: {"references": ["------, 1955 b, New carnivorous dinosaurs from the Upper Cretaceous of Mongolia: Dokladi Akademii Nauk S. S. S. R., v. 104, p. 779 - 782.", "Maleev, E., 1955 a, Gigantic carnivorous dinosaurs of Mongolia: Dokladi Akademii Nauk S. S. S. R., v. 104, p. 634 - 637.", "------, 1974, Giant carnosaurs of the family Tyrannosauridae, in Mesozoic and Cenozoic faunas and biostratigraphy of Mongolia: Transactions of the Joint Soviet-Mongolian Palaeontological Expedition, v. l, p. 132 - 190.", "Rozhdestvensky, A., 1965, Growth changes in Asian dinosaurs and some problems of their taxonomy. paleontologicheskii Zhurnal, p. 95 - 109.", "------, 1912, Crania of Tyrannosaurus and Allosaurus: American Museum of Natural History Memoirs, new series v. 1, p. 1 - 30.", "Carpenter, K., in press, Examples of variation in Tyrannosaurus rex: in Currie, P. and Carpenter, K., eds., Dinosaur Systematics: Cambridge, Cambridge University Press", "Welles, S. and Long, R., 1974, The tarsus of theropod dinosaurs: Annals of the South African Museum, v. 64, p. 191 - 218.", "Lawson, D., 1976, Tyrannosaurus and Torosaurus, Maestrichtian dinosaurs from Trans-Pecos, Texas: Journal of Paleontology 50, p. 158 - 164."]}