''Irisosaurus'' (meaning "iridescent lizard" after the iridescent clouds of

Yunnan Province Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

) is an extinct genus of sauropodiform

sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

, from the

Fengjiahe Formation The Fengjiahe Formation is a geological formation in China. It dates back to the Early Jurassic, most likely to the Pliensbachian. The formation is up to 1500 metres thick and consists of "purple-red mudstone and argillaceous siltstone interbedd ...

of China. 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 ...

, ''Irisosaurus yimenensis'' was formally described in 2020. It was the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to ''

Mussaurus ''Mussaurus'' (meaning "mouse lizard") is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Sinemurian stage of the Early Jurassic. It receives its name from the small size of the skeletons of juvenile and ...

''.

Discovery and naming

The holotype, CVEB 21901, was found in the rocks of the Fengjiahe Formation in Yimen County, Yunnan, during the summer of 2018. In 2020, it was assigned to the new genus and species, ''Irisosaurus yimenensis'', named after the county it was found and "the famous iridescent clouds of Yunnan Province" (; literally "south of colorful clouds", the likely origin of Yunnan's name).

Description

The holotype of ''Irisosaurus'' shows a unique combination of traits that in themselves are not unique. There is a large and deep neurovascular foramen on the perinarial fossa. The premaxillary ramus of the maxilla is higher than it is long prior to the nasal process. The proximal half of metacarpal V is strongly asymmetrical. Irisosaurus Scale

References

{{Taxonbar, from=Q96943141 Anchisauria Dinosaur genera Hettangian dinosaurs Fossil taxa described in 2020 Taxa named by Xu Xing Dinosaurs of China