Antrodemus
Encyclopedia
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
hoofs". 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 dubbed 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.
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....
-Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
-age Upper Jurassic Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
of Middle Park
Middle Park (Colorado basin)
Middle Park is a high basin in the Rocky Mountains of north-central Colorado in the United States. It is located in Grand County, on the southwest slope of Rocky Mountain National Park, approximately 50 miles west of Boulder.-Description:The basin surrounds the headwaters of the Colorado River...
, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
. It contains one species, Antrodemus valens, first described and named as a species of Poekilopleuron
Poekilopleuron
Poekilopleuron is an extinct genus of large basal tetanuran theropod dinosaur, perhaps belonging to the clade Allosauroidea. It measured 9 metres long and 1 ton in mass...
by Joseph Leidy
Joseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
in 1870.
The first described fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
specimen was a bone obtained secondhand by Ferdinand Vandiveer Hayden in 1869. It came from Middle Park, near Granby, Colorado
Granby, Colorado
The Town of Granby is a Statutory Town that is the most populous town in Grand County, Colorado, United States. Granby is situated along U.S. Highway 40 in Middle Park about west of Denver, Colorado, southwest of Rocky Mountain National Park...
, probably from Morrison Formation rocks. The locals had identified such bones as "petrified horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
hoofs". 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
Poekilopleuron
Poekilopleuron is an extinct genus of large basal tetanuran theropod dinosaur, perhaps belonging to the clade Allosauroidea. It measured 9 metres long and 1 ton in mass...
as Poicilopleuron [sic] valens. He later decided it deserved its own genus, Antrodemus.
In 1920, Charles W. Gilmore
Charles W. Gilmore
Charles Whitney Gilmore was an American paleontologist, who named dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus and...
came to the conclusion that the tail vertebra dubbed 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.