The Alethinophidia are an infraorder of snakes that includes all snakes other than blind snakes and thread snakes. Snakes have long been grouped into families within Alethinophidia based on their morphology, especially that of their teeth. More modern phylogenetic hypotheses using genetic data support the recognition of 19 extant families (see below), although the taxonomy of alethinophidian snakes has long been debated, and ultimately the decision whether to assign a particular clade to a particular Linnaean rank (such as a superfamily, family, or subfamily) is arbitrary.

Etymology

The infraorder name Alethinophidia derives from the two Ancient Greek words, meaning "truthful, genuine", and , meaning "snake".

Fossil record

Fossils of alethinophidians were found in Cenomanian (Middle Cretaceous) sites of Wadi Milk Formation in Wadi Abu Hashim, Sudan. Coniophis presents the vertebral morphology similar to modern-day Aniliidae. Two extinct families from the same location, the Anomalophiidae and Russellophiidae, also belong to the Alethinophidia. Krebsophis is the earliest russellophiid. The family Nigerophiidae includes both aquatic Nubianophis from Wadi Abu Hashim and Nigerophis from the Palaeocene of Niger. The genus Eoanilius (belongs to Aniliidae) appeared in the Eocene. It is also existed in Oligocene and early Miocene. The extinct marine Simoliophidae are known from the Cenomanian of North Africa, the Middle East, and Eastern Europe, indicating a Tethyan distribution; they are notable for preserving evidence of vestigial hindlimbs.

Systematics

Extant taxa

Fossil taxa

Based on Gower & Zaher (2022):