Ophidiomorpha

Ophidiomorpha is a proposed clade composed of snakes and a number of extinct squamate groups. The clade was defined by Placi and Caldwell in 2007 as a node-based clade containing the most recent common ancestor of dolichosaurs, adriosaurs, Aphanizocnemus, and fossil and extant Ophidia and all of its descendants.

The existence of Ophidiomorpha as a clade is controversial, as it is placed within the Pythonomorpha (a clade that itself is not universally agreed upon containing mosasaurs and snakes, their most recent common ancestor, and all of that ancestors' descendants). Most 20th-century herpetologists and paleontologists rejected this idea and sought instead to demonstrate a close relationship between mosasaurs and varanid lizards.

Pythonomorpha was later resurrected by a number of paleontologists (Lee, 1997; Caldwell et Lee, 1997) who had conducted cladistic analyses that seemed to show that snakes and mosasaurs may have been more closely related to one another than either were to the varanid lizards, and that snakes more likely arose from aquatic ancestors.

Other authors have rejected the Ophidiomorpha hypothesis, finding that Mosasauria (including dolichosaurs) are unrelated to snakes.