''Omosaurus'' is a dubious

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of extinct crurotarsan reptile, possibly a

phytosaur Phytosaurs (Φυτόσαυροι in greek) are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. Phytosauria and Phytosauridae are often considered to be equivalent gr ...

, from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

(

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followe ...

) of

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia a ...

. Only scant remains are known, which makes ''Omosaurus'' hard to classify. The type, and only species, ''Omosaurus perplexus'', was named and described in 1856 by

Joseph Leidy Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist. Leidy was professor of anatomy at the University of Pennsylvania, later was a professor of natural history at Swarthmore ...

Discovery and naming

In the middle of the nineteenth century,

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, alt ...

Professor Ebenezer Emmons discovered several reptilian teeth in the

colliery Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron fro ...

of the

Chatham company Chatham may refer to: Places and jurisdictions Canada * Chatham Islands (British Columbia) * Chatham Sound, British Columbia * Chatham, New Brunswick, a former town, now a neighbourhood of Miramichi * Chatham (electoral district), New Brunswic ...

. In 1856, the fossils in his collection were described by

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

. Leidy combined the teeth with some vertebrae and ribs; adding to them an

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinc ...

scute A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...

found in the same strata by Professor Michael Tuomey, he named the whole ''Omosaurus perplexus'' based on the holotype specimen BMNH 46013.J. Leidy, (1856), "Notice of remains of extinct vertebrated animals discovered by Professor E. Emmons", ''Proceedings of the Academy of Natural Sciences of Philadelphia'' 8: 255-257 Leidy provided no

etymology Etymology () The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words ...

; the specific name suggests he was intrigued by the "intricate" find. The generic name might be derived from the Greek ὠμός, ''omos'', "rough", perhaps in reference to the rough surface of the scute or to the "savage" nature of a carnivorous reptile. Today, all

syntype In biological nomenclature, a syntype is any one of two or more biological types that is listed in a description of a taxon where no holotype was designated. Precise definitions of this and related terms for types have been established as part of ...

s are lost.

Description

The teeth were described as being rather straight, slightly curved inwards, conical and pointed with a length of up to one inch. They had two edges at the inside and a D-shaped cross-section with the convex part positioned at the outer side. The surface of the teeth was smooth with little wrinkles, running vertically at the inside and horizontally at the outside. The vertebrae were amphicoelous and constricted at the waist, with a length of about three centimetres and somewhat taller than wide in cross-section. The scute was ornamented with a fan-shaped pattern of splitting ridges.

Phylogeny

Leidy himself believed ''Omosaurus'' to be a marine reptile, probably a plesiosaur, suspecting the remains were referable to some already named genus. In 1902,

Frederick Augustus Lucas Frederic Augustus Lucas, Sc.D. (March 25, 1852 – February 9, 1929) was a zoologist who served as a curator of the Brooklyn Museum and director of the American Museum of Natural History. He was an expert on the osteology and anatomy of birds. Bio ...

recognised the fossils as "crocodilian" in nature and placed ''Omosaurus'' in the

Crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

. At the same time he affirmed the priority over ''Omosaurus'' ( Owen 1875), which

stegosaur Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Euro ...

was by him renamed to '' Dacentrurus''. Today, ''Omosaurus'' is commonly listed as a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'', a possible member of the

Phytosauria Phytosaurs (Φυτόσαυροι in greek) are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. Phytosauria and Phytosauridae are often considered to be equivalen ...

References

{{Taxonbar, from=Q1924922 Fossil taxa described in 1856 Crurotarsans Late Triassic reptiles of North America Nomina dubia Prehistoric reptile genera