Antrodemus

''Antrodemus'' ("chamber bodied") is a dubious genus of theropod dinosaur from the Upper Jurassic, probably the 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.

Discovery and species

The first described fossil specimen was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869 (original discoverer unknown). It came from Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. Hayden reported that several similar fossils had been identified 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'' ic''valens'', based on the shared presence of a large medullary cavity. He identified the presence of trabeculae in ''P''. ''valens'' as a distinguishing character from ''P''. ''bucklandii'' but also noted that should better remains show more characters that could sufficiently distinguish the two taxa, it might be named ''Antrodemus''. In 1873, he amended his description and identified the species as ''Antrodemus valens''.

In 1920, Charles W. Gilmore concluded 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 the ''Allosaurus'' 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''.

The paleontological site that still in the present day presents the highest concentration of fossilised individuals of ''Allosaurus fragilis'' is the Cleveland-Lloyd Dinosaur Quarry, now part of the Jurassic National Monument in Utah. The first skeletal mount obtained out of the Quarry was extracted in the late 1930s/early 1940s and finally mounted in 1961 in Guyot Hall, Princeton University, Princeton, New Jersey, where it remained on display until 2024. For years, that skeletal mount was presented to the visitors under the taxonomic name ''Antrodemus'', before the specimens from the Cleveland-Lloyd Quarry were attributed to ''Allosaurus''.

References

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{{Taxonbar, from=Q772822

Carnosauria
Dinosaur genera
Kimmeridgian dinosaurs
Morrison Formation
Dinosaurs of the United States
Fossil taxa described in 1873
Taxa named by Joseph Leidy