''Omosaurus'' is a

dubious Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty, ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

crurotarsan Crurotarsi is a clade of archosauriform reptiles that includes crocodilians and stem-crocodilians and possibly bird-line archosaurs too if the extinct, crocodile-like phytosaurs are more distantly related to crocodiles than traditionally thoug ...

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

, 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 ...

, 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 followed by t ...

) 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 and So ...

. 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, althou ...

Professor

Ebenezer Emmons Ebenezer Emmons (May 16, 1799October 1, 1863), was a pioneering American geologist whose work includes the naming of the Adirondack Mountains in New York as well as a first ascent of Mount Marcy. Early life Emmons was born at Middlefield, Massac ...

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 from ...

of the Chatham company in

. 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 fossi ...

. 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 (extinct amp ...

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 Michael Tuomey (September 29, 1805 – March 30, 1857) was the State Geologist of South Carolina from 1844 to 1847, and the first State Geologist of Alabama, appointed in 1848 and serving until his death. His early descriptions and maps of the Bi ...

, 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 Phonological chan ...

; 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 The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

, suspecting the remains were referable to some already named genus. In 1902, Frederick Augustus Lucas 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 living ...

. At the same time he affirmed the priority over ''Omosaurus'' (

Owen Owen may refer to: Origin: The name Owen is of Irish and Welsh origin. Its meanings range from noble, youthful, and well-born. Gender: Owen is historically the masculine form of the name. Popular feminine variations include Eowyn and Owena. ...

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, Europe, ...

was by him renamed to ''

Dacentrurus ''Dacentrurus'' (meaning "tail full of points"), originally known as ''Omosaurus'', is a genus of stegosaurian dinosaur from the Late Jurassic to Early Cretaceous (154 - 140 mya) of Europe. Its type species, ''Omosaurus armatus'', was named in 18 ...

''. 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 equivalent ...

References

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