Stereospondyli

The Stereospondyli are a group of extinct temnospondyl amphibians that existed primarily during the Mesozoic period. They are known from all seven continents and were common components of many Triassic ecosystems, likely filling a similar ecological niche to modern crocodilians prior to the diversification of pseudosuchian archosaurs.

== Classification and anatomy == The group was first defined by Zittel (1888) on the recognition of the distinctive vertebral anatomy of the best known stereospondyls of the time, such as Mastodonsaurus and Metoposaurus. The term 'stereospondylous' as a descriptor of vertebral anatomy was coined the following year by Fraas, referring to a vertebral position consisting largely or entirely of the intercentrum in addition to the neural arch. While the name 'Stereospondyli' is derived from the stereospondylous vertebral condition, there is a diversity of vertebral morphologies among stereospondyls, including the diplospondylous ('tupilakosaurid') condition, where the arch sits between the corresponding intercentrum and pleurocentrum, and the plagiosaurid condition, where a single large centrum ossification (identity unknown) is present, and the arch sits between subsequent vertebral positions. The concept of Stereospondyli has thus undergone repeated and frequent revisions by different workers. Defining features include a tight articulation between the parasphenoid and the pterygoid and a stapedial groove.