STL Science Center

STL Science Center

02 September 2014

Describe and Revise

Mader and Bradley (1989) redescribed Alectrosaurus by revisiting the syntypes of the dinosaur that were unearthed by George Olsen in Mongolia in 1923. Gilmore described the dinosaur as a "Deinodont" (synonymous with "tyrannosaurid") that was similar to Gorgosaurus. Gilmore was very confident in considering this dinosaur a tyrannosaurid, but many more recent phylogenetic and systematics studies have questioned the validity of the assignment based on the fragmentary materials. Mader and Bradley turned the dinosaur upside down, but retained the tyrannosaurid connections. In fact, they considered it close enough to ally it with Tarbosaurus. They added previously unassigned caudal vertebrae (AMNH 21784) while eliminating some of the syntype material (forelimbs labeled AMNH 6368) based on the length of the limbs it portrayed. This places it in the Tyrannosauridae, however, Loewen et al. (2013) places Alectrosaurus in a more basal position outside of the Tyrannosauridae. Part of this study included the information that was compiled in Carr (2005) and is laid out in an easier to read list on Wikipedia. The swaying of assignment for this dinosaur has not been tumultuous at all. The only real swaying that it has done, actually, is in and out of the Tyrannosauridae family. At the moment it is outside of that family and is assigned only into the superfamily Tyrannosauroidea., but it has been considered a true tyrannosaur, an Albertosaur, an ally of Tarbosaurus, and it started out as an unknown theropod. Alectrosaurus has come a long way and, like many other dinosaurs, is still disputed, but is obviously loved by enough people to maintain its popularity.

Carr, 2005. Phylogeny of Tyrannosauroidea (Dinosauria: Coelurosauria) with special reference to North American forms. Unpublished PhD dissertation. University of Toronto. 1170 pp.

Loewen, M.A.; Irmis, R.B.; Sertich, J.J.W.; Currie, P. J.; Sampson, S. D. 2013. "Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans". In Evans, David C. PLoS ONE 8 (11): e79420.

Mader, B.J., and Bradley, R.L. 1989. A redescription and revised diagnosis of the syntypes of the Mongolian tyrannosaur Alectrosaurus olseni. Journal of Vertebrate Paleontology 9(1):41-55.

No comments:

Post a Comment