Temporal range: Late Jurassic,
150 Ma
Holotype tail vertebra (above) compared to same of Allosaurus (below)
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Allosauridae
Genus: Antrodemus
Leidy, 1873
A. valens
Binomial name
Antrodemus valens
(Leidy, 1870 [originally Poekilopleuron])

Antrodemus ("chamber bodied") 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 Vandeveer 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.[citation needed] 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.[3] He later decided it deserved its own genus, Antrodemus.[4]

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.[5] 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).[6] Subsequent authors have agreed with this assessment and have considered Antrodemus a nomen dubium.[7][8]


  1. ^ Riabinin, 1915. Zamtka o dinozavry ise Zabaykalya [A note on a dinosaur from the trans-Baikal region]. Trudy Geologichyeskago Muszeyah Imeni Petra Velikago Imperatorskoy Academiy Nauk. 8(5), 133-140.
  2. ^ Huene, 1932. Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte. Monographien zur Geologie und Palaeontologie. 4(1), viii + 361 pp.
  3. ^ Leidy, Joseph (1870). "Remarks on Poicilopleuron valens, Clidastes intermedius, Leiodon proriger, Baptemys wyomingensis, and Emys stevensonianus". Proceedings of the Academy of Natural Sciences of Philadelphia. 22: 3–4.
  4. ^ Leidy, Joseph (1873). "Contribution to the extinct vertebrate fauna of the western territories". Report of the U.S. Geological Survey of the Territories I: 14–358.
  5. ^ Gilmore, Charles W. (1920). "Osteology of the carnivorous dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus". Bulletin of the United States National Museum. 110 (110): 1–159. doi:10.5479/si.03629236.110.i. hdl:2027/uiug.30112032536010.
  6. ^ Madsen, James H., Jr. (1993) [1976]. Allosaurus fragilis: A Revised Osteology. Utah Geological Survey Bulletin 109 (2nd ed.). Salt Lake City: Utah Geological Survey.
  7. ^ Paul, Gregory S.; Carpenter, Kenneth (2010). "Case 3506: Allosaurus Marsh, 1877 (Dinosauria, Theropoda): proposed conservation of usage by designation of a neotype for its type species Allosaurus fragilis Marsh, 1877" (PDF). The Bulletin of Zoological Nomenclature. 67 (1): 53–56. doi:10.21805/bzn.v67i1.a7. S2CID 81735811.
  8. ^ Rauhut, Oliver W. M. (2011). "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology. 86: 195–239. doi:10.1111/j.1475-4983.2011.01084.x (inactive 2021-01-10).CS1 maint: DOI inactive as of January 2021 (link)