The Caenophidia are a derived

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of alethinophidian

snakes Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joi ...

, which contains over 80% of all the extant species of snakes. The largest family is

Colubridae Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...

, but it also includes at least seven other families, at least four of which were once classified as "Colubridae" before molecular phylogenetics helped us understand their relationships. It has been found to be

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. Although the Caenophidia previously was held to exclude

Acrochordidae The Acrochordidae, commonly known as wart snakes, Java wart snakes, file snakes, elephant trunk snakes, or dogface snakes are a monogeneric family created for the genus ''Acrochordus''. This is a group of basal aquatic snakes found in Australia a ...

, researchers have recognized that acrochordids share several traits with the other caenophidians. Hence Caenophidia is usually considered to comprise Acrochordidae plus more the more derived snakes classified as Colubroidea. Recent molecular studies have also found the families

Xenophidiidae ''Xenophidion'' is a genus of snakes first described in 1995, and the only genus of the monotypic family Xenophidiidae.. Commonly referred to as spinejaw snakes, this genus is found in Borneo and peninsular Malaysia. Morphology and classificatio ...

and

Bolyeriidae :''Common names: Mauritius snakes, Round Island boas, splitjaw snakes.'' The Bolyeriidae are a family of snakes native to Mauritius and a few islands around it, especially Round Island. They also used to be found on the island of Mauritius, but ...

to be closely related to caenophidians, forming the sister group to Caenophidia rather than being part of

Henophidia Henophidia is a former superfamily of the suborder Serpentes (snakes) that contains boas, pythons and numerous other less-well-known snakes. Snakes once considered to belong to superfamily Henophidia include two families now considered Ameroph ...

. Below is a phylogeny of the Caenophidia based on analyses from several studies:

References

Alethinophidia Extant Santonian first appearances {{Alethinophidia-stub