Ophidia

Ophidians Temporal range: Middle Jurassic – Holocene, 170–0 Ma PreЄ Є O S D C P T J K Pg N
Coast garter snake, Thamnophis elegans terrestris
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	Toxicofera
Clade:	Ophidia Latreille, 1804
Subgroups
†Coniophis †Diablophis †Dinilysia †Eophis †Lapparentophis †Najash †Pachyrhachis †Parviraptor †Portugalophis †Mesophis †Madtsoiidae? †Tetrapodophis Serpentes

†Coniophis
†Diablophis
†Dinilysia
†Eophis
†Lapparentophis
†Najash
†Pachyrhachis
†Parviraptor
†Portugalophis
†Mesophis
†Madtsoiidae?
†Tetrapodophis
Serpentes

Ophidia (also known as Pan-Serpentes) is a group of squamate reptiles including modern snakes and all reptiles more closely related to snakes than to other living groups of lizards.

Modern snakes are thought to have evolved from either burrowing or aquatic lizards during the mid-Cretaceous period, and the earliest known fossils date to around 112 Ma ago. However, the relationship between modern snake and more primitive snake ancestors, many of which retained hind limbs, is less clear. While many of these "stem-snakes" are known from Mesozoic fossils, some of them may be descendants of the earliest true snakes rather than more primitive lineages. Below is a cladogram modified from a study by Wilson et al. (2010), which found many stem-snakes of other studies to be true snakes instead.