DalinghesaurusLongidigitus-PaleozoologicalMuseumOfChina-May23-08

Shinisauria is a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

or evolutionary grouping of

anguimorph The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to '' Varanus'' and ''Anguis'' than ''Scincus''. These lizards, along with iguanians and snakes, constitute the propose ...

lizards that includes the living

Chinese crocodile lizard The Chinese crocodile lizard (''Shinisaurus crocodilurus'') is a semiaquatic anguimorph lizard found only in cool forests in southeastern China and northeastern Vietnam. The Chinese crocodile lizard spends much of its time in shallow water or in ...

''Shinisaurus'' and several of its closest extinct relatives. Shinisauria was named in 2008 by Jack Lee Conrad as a

stem-based taxon Phylogenetic nomenclature is a method of nomenclature for taxon, taxa in biology that uses phylogenetics, phylogenetic definitions for taxon names as explained below. This contrasts with Biological classification, the traditional method, by which ...

to include all anguimorphs more closely related to ''Shinisaurus'' than to ''

Anguis fragilis The common slow worm (''Anguis fragilis'') is a species of legless lizard native to western Eurasia. It is also called a deaf adder, blindworm, or regionally, a long-cripple, steelworm, and hazelworm. The "blind" in blindworm refers to the lizar ...

'', ''

Heloderma suspectum The Gila monster (''Heloderma suspectum'', ) is a species of venomous lizard native to the Southwestern United States and the northwestern Mexican state of Sonora. It is a heavy, slow-moving reptile, up to long, and it is the only venomous ...

'' or '' Varanus varius''. Several recent

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses of lizard evolutionary relationships place Shinisauria in a basal position within the clade Platynota, which also includes

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and West African Nile monitor, one species is also found in south America as an invasive species. A ...

s, helodermatids, and the extinct

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...

s. Shinisaurians were once thought to be closely related to the genus ''

Xenosaurus ''Xenosaurus'' is a genus of lizards; it is the only extant genus in the family Xenosauridae, with 14 species currently recognized."Xenosauridae" and "''Xenosaurus'' ". The Reptile Database. www.reptile-database.org. Also known as knob-scaled li ...

'', but they are now considered distant relatives within Anguimorpha. The fossil record of shinisaurians extends back to the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

with '' Dalinghosaurus'', which is from the

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

aged

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

of China. Two other extinct shinisaurians are currently known: '' Bahndwivici'' from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

of Wyoming and '' Merkurosaurus'' from the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

of Germany and the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

of the Czech Republic. An indeterminate shinisaurian is known from an isolated tail found in the Eocene aged

Messel pit The Messel Formation is a Formation (geology), geologic formation in Hesse, central Germany, dating back to the Eocene Epoch (geology), epoch (about 47 Ma). Its geographic range is restricted to the Messel pit. There it unconformably overlie ...

in Germany.

References

Anguimorpha Tetrapod unranked clades {{lizard-stub