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Tyrannosaurid Systematics

Thomas R. Holtz, Jr.
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Daspletosaurus torosus at rest

The late Campanian North American Daspletosaurus torosus at rest. © 1997, Michael Skrepnick.

The following represent the synapomorphies supporting the phylogeny presented in the Tyrannosauridae page, and are based on analyses of Holtz (in press a, b).

The monophyly of Aublysodontinae is only weakly supported by two premaxillary tooth characters:

Note that the first of these may be a preservational artifact. Aublysodontine form teeth are reported in the skulls of Alectrosaurus olseni, Aublysodon molnari, and an unnamed new taxon from the Kirtland Shale of northwestern New Mexico (Lehman and Carpenter 1990). While the latter taxon is comparable in size to the larger tyrannosaurines, the former two are considerably smaller. As aublysodontines are at present only known from fragmentary specimens, and are otherwise characterized by plesiomorphic features transformed in Tyrannosaurinae, future analyses may show that some taxa currently in Aublysodontinae are more closely related to the tyrannosaurines.


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 skull of Alioramus remotus

The skull of the primitive early Maastrichtian Mongolian tyrannosaurid Alioramus remotus. © 1995, Tracy Lee Ford.

Tyrannosaurinae is diagnosed by the following features:

Tyrannosaurinae as used here comprises the taxon Alioramus remotus (which shares several derived braincase characters with Albertosaurus, Tarbosaurus, and Tyrannosaurus), Albertosaurus sarcophagus, Gorgosaurus libratus, Daspletosaurus torosus, an unnamed taxon from the upper Two Medicine Formation, Tarbosaurus bataar, and Tyrannosaurus rex.

Tyrannosaurines other than Alioramus share the following derived characters:

Additionally, the following features are currently known only for these advanced tyrannosaurines, but may be more widely distributed. However, incompleteness of currently known specimens of Aublysodontinae and Alioramus prevents confirmation of the exact distribution of these characters:

The poorly-known Shanshanosaurus houyanshanensis shares with the advanced tyrannosaurines a reduced maxillary and dentary tooth count. Additional features demonstrate the tyrannosaurid nature of this taxon (Holtz in press a, b), but its precise position among the tyrant dinosaur cannot be established pending more detailed study of the specimen.

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skull of Gorgosaurus libratus

The skull of the late Campanian North American tyrannosaurine Gorgosaurus libratus. © 2000, Thomas R. Holtz, Jr.

Although many authors (Russell 1970, Paul 1988, Carpenter 1992) have united Albertosaurus sarcophagus and Gorgosaurus libratus in the same genus (Albertosaurus by principle of priority), most of the characters used to justify this union represent plesiomorphies lacking in the more derived tyrannosaurines. As in Holtz (in press a, b) the original generic names are retained. Two potential synapomorphies joining Albertosaurus and Gorgosaurus are:

However, in trees equally parsimonious to those uniting Albertosaurus and Gorgosaurus, other characters justify union of Gorgosaurus and the Daspletosaurus-Tarbosaurus-Tyrannosaurus clade to the exclusion of Albertosaurus.

A clade of robust tyrannosaurines is supported by the following derived features:

This clade contains Daspletosaurus, an unnamed form from the Two Medicine Formation (briefly described in Horner et al. 1992), Tarbosaurus, and Tyrannosaurus. The Two Medicine tyrannosaurine shares some derived features with Daspletosaurus, and others with Tarbosaurus and/or Tyrannosaurus, so that its phylogenetic position is currently unresolved (Holtz in press b).

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skull of Tarbosaurus bataar skull of Tyrannosaurus rex

The skulls of the giant Maastrichtian species Tarbosaurus bataar of Mongolia (left) and Tyrannosaurus rex of North America (right).
Tarbosaurus photo © 1996, Thomas R. Holtz, Jr.; Tyrannosaurus photo © 1993, Michael K. Brett-Surman.


Tyrannosaurus and Tarbosaurus are united by several synapomorphies:

Some authors (Paul 1988, Carpenter 1992, Holtz 1994, in press a, in press b) retain the use of the original name Tyrannosaurus bataar for the large Nemegt Formation tyrannosaurine. Following Carr (1999) and Holtz (in press a, b) the taxa Maleevosaurus novojilovi, Gorgosaurus lancinator, and Tarbosaurus efremovi are regarded as different early ontogenetic stages of Tarbosaurus bataar, and Nanotyrannus lancensis and Albertosaurus megagracilis as a juvenile and subadult specimen of Tyrannosaurus rex, respectively.

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skull of Daspletosaurus torosus

The skull of the late Campanian North American tyrannosaurine Daspletosaurus torosus. © 1995, Tracy Lee Ford.


Carpenter, K. 1992. Tyrannosaurids (Dinosauria) of Asia and North America. In: Mateer, N., and Chen P.-J. (eds.) Aspects of Nonmarine Cretaceous Geology. China Ocean Press, Beijing. Pp. 250-268.

Carr, T. D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19: 497-520.

Holtz, T. R., Jr. 1994. The phylogenetic position of the Tyrannosauridae: implication for theropod systematics. Journal of Paleontology 68: 1100-1117.

Holtz, T. R., Jr. in press a. Tyrannosauridae. In: Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. Second Edition. University of California Press, Berkeley.

Holtz, T. R., Jr. in press b. The phylogeny and taxonomy of the Tyrannosauridae. In: Carpenter, K., and Tanke, D. (eds.). Mesozoic Vertebrate Life. Indiana University Press.

Horner, J. R., Varricchio, D. J., and Goodwin, M. B. 1992. Marine transgressions and the evolution of Cretaceous dinosaurs. Nature 358: 59-61.

Hurum, J. H., and Currie, P. J. 2000. The crushing bite of tyrannosaurids. Journal of Vertebrate Paleontology 20: 619-621.

Lehman, T. M., and Carpenter, K. 1990. A partial skeleton of the tyrannosaurid dinosaur Aublysodon from the Upper Cretaceous of New Mexico. J. Paleontol. 64: 1026-1032.

Paul, G. S. 1988. Predatory Dinosaurs of the World. Simon and Schuster, New York. 464 pp.

Russell, D. A. 1970. Tyrannosaurs from the Late Cretaceous of western Canada. National Museum National Science Publications in Palaeontology 1: 1-34.


About This Page

Thomas R. Holtz, Jr.
University of Maryland, College Park, Maryland, USA

All Rights Reserved.

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