If you need an accessible version of this item please contact JSTOR User Support

The Phylogenetic Position of the Tyrannosauridae: Implications for Theropod Systematics

Thomas R. Holtz, Jr.
Journal of Paleontology
Vol. 68, No. 5 (Sep., 1994), pp. 1100-1117
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1306180
Page Count: 18
  • Download PDF
  • Cite this Item

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support
The Phylogenetic Position of the Tyrannosauridae: Implications for Theropod Systematics
Preview not available

Abstract

Tyrannosaurids are a well-supported clade of very large predatory dinosaurs of Late Cretaceous Asiamerica. Traditional dinosaurian systematics place these animals within the infraorder Carnosauria with the other large theropods (allosaurids, megalosaurids). A new cladistic analysis indicates that the tyrannosaurs were in fact derived members of the Coelurosauria, a group of otherwise small theropods. Despite certain gross cranial similarities with the large predators of the Jurassic and Early Cretaceous, the Late Cretaceous tyrannosaurids are shown to be the sister group to ornithomimids and troodontids, which share a derived condition of the metatarsus. This clade is found to be nested within Maniraptora, which is a more inclusive taxon than previously recognized. The atrophied carpal structure found in tyrannosaurids and ornithomimids is derived from a maniraptoran condition with a large semilunate carpal, rather than from the plesiomorphic theropod morphology. The taxa "Carnosauria" and "Deinonychosauria" (Dromaeosauridae plus Troodontidae) are shown to be polyphyletic, and the Late Jurassic African form Elaphrosaurus is found to be the sister taxon to Abelisauridae rather than a primitive ornithomimosaur. Purported allosaurid-tyrannosaurid synapomorphies are seen to be largely size-related, present in the larger members of both clades, but absent in smaller members of the Tyrannosauridae. The remaining giant tetanurine theropods (Megalosaurus and Torvosaurus) were found to be progressively distant outgroups to an allosaurid-coelurosaur clade. The inclusion of the Tyrannosauridae within Maniraptora suggests a major adaptive radiation of coelurosaurs within Cretaceous Asiamerica comparable to contemporaneous radiations in various herbivorous dinosaurian clades.

Page Thumbnails

  • Thumbnail: Page 
1100
    1100
  • Thumbnail: Page 
1101
    1101
  • Thumbnail: Page 
1102
    1102
  • Thumbnail: Page 
1103
    1103
  • Thumbnail: Page 
1104
    1104
  • Thumbnail: Page 
1105
    1105
  • Thumbnail: Page 
1106
    1106
  • Thumbnail: Page 
1107
    1107
  • Thumbnail: Page 
1108
    1108
  • Thumbnail: Page 
1109
    1109
  • Thumbnail: Page 
1110
    1110
  • Thumbnail: Page 
1111
    1111
  • Thumbnail: Page 
1112
    1112
  • Thumbnail: Page 
1113
    1113
  • Thumbnail: Page 
1114
    1114
  • Thumbnail: Page 
1115
    1115
  • Thumbnail: Page 
1116
    1116
  • Thumbnail: Page 
1117
    1117