Corosaurus is an extinct 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 pistosauroid known from Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

 of the USA.

Description

Corosaurus is known from the holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 UW

University of Wyoming

The University of Wyoming is a land-grant university located in Laramie, Wyoming, situated on Wyoming's high Laramie Plains, at an elevation of 7,200 feet , between the Laramie and Snowy Range mountains. It is known as UW to people close to the university...

 5485, a partial skeleton

Skeleton

The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 which includes the skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

. Later, the referred specimens YPM 41030-41068, FMNH

Field Museum of Natural History

The Field Museum of Natural History is located in Chicago, Illinois, USA. It sits on Lake Shore Drive next to Lake Michigan, part of a scenic complex known as the Museum Campus Chicago...

 PR 135, FMNH PR 1368-1369, FMNH PR 242-246 and FMNH PR 1382-1383 were described by Glenn William Storrs in 1991. All specimens were collected in Jackson Canyon, Natrona County, from the Chugwater Group of the Alcova Limestone Formation, dating to the late Olenekian

Olenekian

In the geologic timescale, the Olenekian is an age in the Early Triassic epoch or a stage in the Lower Triassic series. It spans the time between 249.7 ± 0.7 Ma and 245 ± 0.7 Ma . The Olenekian follows the Induan and is followed by the Anisian.The Olenekian saw the deposition of a large part of the...

 stage of the late Early Triassic

Early Triassic

The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy...

, about 247.4-245 million years ago. After a revision of the holotype and referred material of Corosaurus, Olivier Rieppel found Corosaurus to be the sister-taxon to a clade comprising Cymatosaurus

Cymatosaurus

Cymatosaurus is an extinct genus of pistosauroid sauropterygian. It is known from Early Triassic to the Middle Triassic period of Germany....

, Pistosaurus

Pistosaurus

Pistosaurus longaevus is an extinct genus of aquatic sauropterygian reptile closely related to plesiosaurs. Fossils have been found in France and Germany, and date to the Middle Triassic.- Appearance :...

and Plesiosauria

Plesiosauria

Plesiosauria is an order of Mesozoic marine reptiles. Plesiosaurs first appeared in the Early Jurassic Period and became especially common during the Jurassic Period, thriving until the K-T extinction at the end of the Cretaceous Period.The name "plesiosaur" is used to refer to the order...

.

Etymology

Corosaurus was first named by Ermine Cowles Case

Ermine Cowles Case

Ermine Cowles Case , invariably known as E.C. Case, was a prominent American paleontologist in the second generation that succeeded Othniel Charles Marsh and Edward Drinker Cope...

 in 1936

1936 in paleontology

-Insects:-Newly named dinosaurs:Data courtesy of George Olshevsky's dinosaur genera list and Dr. Jeremy Montague's dinosaur genus database.-New taxa:-Non-mammalian:...

 and the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 is Corosaurus alcovensis. The specific name is derived from the name of the Alcova Limestone Formation, in which the holotype was found. Corosaurus was placed in its own family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, Corosauridae, which named by Oskar Kuhn

Oskar Kuhn

Oskar Kuhn was a German palaeontologist.-Life and career:Kuhn was educated in Dinkelsbühl and Bamberg and then studied natural science, specialising in geology and paleontology, at the University of Munich, from which he received his D. Phil...

, in 1961.