Antrodemus

Antrodemus Temporal range: Late Jurassic, 150 Ma PreЄ Є O S D C P T J K Pg N ↓
Holotype tail vertebra (above) compared to same of Allosaurus (below)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Clade:	†Carnosauria
Clade:	†Allosauria
Family:	†Allosauridae
Genus:	†Antrodemus Leidy, 1873
Species:	† A. valens
Binomial name
Antrodemus valens (Leidy, 1870 [originally Poekilopleuron])
Synonyms
Poekilopleuron valens Leidy, 1870 Megalosaurus valens (Leidy, 1870 [originally Poekilopleuron])

Antrodemus is a dubious genus of theropod dinosaur from the Kimmeridgian-Tithonian-age Upper Jurassic Morrison Formation of Middle Park, Colorado. It contains one species, Antrodemus valens, first described and named as a species of Poekilopleuron by Joseph Leidy in 1870.

The first described fossil specimen was a bone obtained secondhand by Ferdinand Vandiveer Hayden in 1869. It came from Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. The locals had identified such bones as petrified horse hooves. Hayden sent his specimen to Joseph Leidy, who identified it as half of a tail vertebra, and tentatively assigned it to the European dinosaur genus Poekilopleuron as Poicilopleuron [sic] valens. He later decided it deserved its own genus, Antrodemus.

In 1920, Charles W. Gilmore came to the conclusion that the tail vertebra named Antrodemus by Leidy was indistinguishable from those of Allosaurus, and that Antrodemus should be the preferred name because, as the older name, it had priority. Antrodemus became the accepted name for this familiar genus for over fifty years, until James Madsen published on the Cleveland-Lloyd specimens of Allosaurus and concluded that name should be used because Antrodemus was based on material with poor, if any, diagnostic features and locality information (for example, the geological formation that the single bone of Antrodemus came from is unknown). Subsequent authors have agreed with this assessment and have considered Antrodemus a nomen dubium.