Friday, March 13, 2009

Taxonomy


Rough phylogeny of snakes
Modern snakes
Scolecophidia

Leptotyphlopidae



Anomalepididae



Typhlopidae




Alethinophidia

Anilius


Core Alethinophidia
Uropeltidae

Cylindrophis



Anomochilus



Uropeltinae




Macrostomata
Pythonidae

Pythoninae



Xenopeltis



Loxocemus



Caenophidia

Colubroidea



Acrochordidae



Boidae

Erycinae



Boinae



Calabaria




Ungaliophiinae




Tropidophiinae





A phylogenetic overview of the extant groups, note that the tree only indicates relationships not evolutionary branching times.

All modern snakes are grouped within the suborder Serpentes in Linnean taxonomy, part of the order Squamata, though their precise placement within squamates is controversial. There are two infraorders of Serpentes: Alethinophidia and Scolecophidia. This separation is based on morphological characteristics and mitochondrial DNA sequence similarity. Alethinophidia is sometimes split into Henophidia and Caenophidia, with the latter consisting of "Colubroid" snakes (colubrids, vipers, elapids, hydrophiids, and attractaspids) and acrochordids, while the other alethinophidian families comprise Henophidia. While not extant today, the Madtsoiidae, a family of giant, primitive, python-like snakes, was around until 50,000 years ago in Australia, represented by genera such as Wonambi.

There are numerous debates in the systematics within the group. For instance, many sources classify Boidae and Pythonidae as one family, while some keep the Elapidae and Hydrophiidae, separate for practical reasons despite their extremely close relation.

Recent molecular studies support the monophyly of the clades of modern snakes, scolecophidians, typhlopids + anomalepidids, alethinophidians, core alethinophidians, uropeltids (Cylindrophis, Anomochilus, uropeltines), macrostomatans, booids, boids, pythonids and caenophidians.

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