extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
Wyoming
Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
of the United States. The holotype measured about long, while larger specimens would have belonged to individuals measuring more than long.
History of discovery
''Corosaurus'' is known from the
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
skeleton
A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...
which includes the
skull
The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate.
In the human, the skull comprises two prominent ...
. Later, the referred specimens YPM 41030-41068, FMNH 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
Alcova is a census-designated place (CDP) in Natrona County, Wyoming, Natrona County, Wyoming, United States. It is part of the Casper, Wyoming Metropolitan Statistical Area. The population was 34 at the United States Census 2020, 2020 census. Wyo ...
, dating to the late
Olenekian
In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...
stage of the late
Early Triassic
The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...
, about 247.4-245
million years ago
Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds.
Usage
Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
1936
Events January–February
* January 20 – The Prince of Wales succeeds to the throne of the United Kingdom as King Edward VIII, following the death of his father, George V, at Sandringham House.
* January 28 – Death and state funer ...
and the
type species
In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
is ''Corosaurus alcovensis''. The specific name is derived from the name of the Alcova Limestone Formation, in which the holotype was found.
Classification
''Corosaurus'' was placed in its own
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
, Corosauridae, which named by Oskar Kuhn, in 1961. 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'' is an extinct genus of pistosauroid or nothosauriform sauropterygian. It is known to have been alive from the Early Triassic to the Middle Triassic period (latest Olenekian to Anisian stages) of Germany
Germany, offici ...
'', ''
Pistosaurus
''Pistosaurus'' (exact etymology uncertain) 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. It contains a single species, ''Pi ...
'' and
Plesiosauria
The Plesiosauria or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeared in the latest Triassic Period, possibly in the Rhaetian stage, about 203 million year ...