''Irenosaurus'' is a

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 nom ...

choristodere Choristodera (from the Greek χωριστός ''chōristos'' + δέρη ''dérē'', 'separated neck') is an extinct order of semiaquatic diapsid reptiles that ranged from the Middle Jurassic, or possibly Triassic, to the late Miocene (168 to ...

, a type of amphibious reptile. It is known from a single fragmentary

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

l skeleton (

PIN A pin is a device used for fastening objects or material together. Pin or PIN may also refer to: Computers and technology * Personal identification number (PIN), to access a secured system ** PIN pad, a PIN entry device * PIN, a former Dutch ...

3386/2), discovered in the Aptian-age

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eig ...

Hühteeg Formation at Hüren Dukh, central

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. The

type species In 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 species that contains the biological type specime ...

is ''I. egloni'', which was originally described as a new species of the related choristodere ''

Tchoiria ''Tchoiria'' is a genus of simoedosaurid choristodere, a type of crocodile-like aquatic reptile. Fossils of this genus have been found in Early Cretaceous-age rocks in Mongolia. Four species have been named, but two have been given their own ...

'' in 1983 by Efimov. Efimov transferred the species to the new genus ''Irenosaurus'' in 1988. Evans and Hecht (1993) questioned the separation of the taxon from ''Tchoiria namsarai'' from the same locality on the grounds that the differences between the two may not have been greater than those of various species of the choristodere ''

Champsosaurus ''Champsosaurus'' is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian-Paleocene). The name ''Champsosaurus'' is thought to come from , () ...

''. A later review by Efimov and Storrs (2000) retained the two as separate, noting that some characteristics of ''Irenosaurus'' are more like ''

Khurendukhosaurus ''Khurendukhosaurus'' is a genus of choristodere, a type of amphibious reptile. It is known from Lower Cretaceous rocks of Mongolia and Russia. Two species have been named. The type species, ''K. orlovi'', was named in 1984 by Sigogneau–Rus ...

'', also known from the same site, at the same time recognizing the difficulties of distinguishing three genera from the same locality. ''Irenosaurus'' was a small choristodere, approximately long. It is known from what are interpreted as lake deposits.

References

Choristodera Early Cretaceous reptiles of Asia Fossil taxa described in 1988 Prehistoric reptile genera {{Cretaceous-reptile-stub