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

Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

), 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 lon ...

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

, 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 interbedded ...

of China. 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 specimen ...

, ''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 t ...

to ''

Mussaurus ''Mussaurus'' (meaning " mouse lizard") is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Early Jurassic, with a maximum age of 192.78 ± 0.14 Ma. It receives its name from the small size of the sk ...

''.

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

Anchisauria Hettangian life Early Jurassic dinosaurs of Asia Fossils of China Paleontology in Yunnan Fossil taxa described in 2020 Taxa named by Xu Xing {{Sauropodomorph-stub