Proahaetulla is a monotypic genus of vine snake in the family Colubridae. It contains only one species, the keeled vine snake (Proahaetulla antiqua), which is endemic to the Western Ghats of India. Its natural habitat is montane rainforests of southern Western Ghats.

Discovery

The species was first discovered in 2011, when an individual was found in the Agasthyamalai Hills of Tamil Nadu and Kerala. It was initially thought to be a new species of Ahaetulla, as it looked very similar to the species Ahaetulla dispar. However, genetic analyses found it to be deeply divergent from any member in the genus Ahaetulla, so it was classified in its own genus. Both the genus and species were ultimately described in 2019.

Etymology

The genus name Proahaetulla indicates the early divergence from Ahaetulla. The species name antiqua is Latin for "antique" or "old", referencing the relatively old evolutionary divergence of the taxon.

Taxonomy

Proahaetulla is considered to be the sister taxon to the genus Ahaetulla, which it diverged from an estimated 26.57 million years ago, during the mid-Oligocene. Due to its age, Proahaetulla may be one of the oldest monotypic lineages of snakes to still persist in the Western Ghats. Proahaetulla is also the first deeply divergent snake genus to be described from the Western Ghats in over a century; numerous Indian snake species have had new genera created to reclassify them from the genera they were originally classified in, but Proahaetulla is completely new, possibly having never been encountered by science prior to its description as a new genus and species.

Proahaetulla belongs to the vine snake subfamily Ahaetuliinae, and its relationships to many of the other species within Ahaetuliinae can be shown in the cladogram below, with possibly paraphyletic species noted:

Ahaetuliinaesharp‑nosed snakes Ahaetulla Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans Ahaetulla prasina (paraphyletic) Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic) Ahaetulla fronticincta Proahaetulla antiqua Dryophiops Dryophiops rubescens Dryophiops philippina broad‑nosed snakes Dendrelaphis Dendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus Dendrelaphis formosus Dendrelaphis tristis Dendrelaphis subocularis Dendrelaphis schokari Dendrelaphis fuliginosus Dendrelaphis caudolineatus Chrysopelea Chrysopelea paradisi Chrysopelea ornata Chrysopelea pelias Chrysopelea taprobanica
sharp‑nosed snakesAhaetulla Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans Ahaetulla prasina (paraphyletic) Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic) Ahaetulla fronticincta Proahaetulla antiqua Dryophiops Dryophiops rubescens Dryophiops philippina
Ahaetulla Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans Ahaetulla prasina (paraphyletic) Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic) Ahaetulla fronticincta Proahaetulla antiqua
AhaetullaAhaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans Ahaetulla prasina (paraphyletic) Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic) Ahaetulla fronticincta
Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans Ahaetulla prasina (paraphyletic)
Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic) Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans
Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata Ahaetulla prasina (paraphyletic)
Ahaetulla prasina (paraphyletic) Ahaetulla fasciolata
Ahaetulla prasina (paraphyletic)
Ahaetulla fasciolata
Ahaetulla prasina (paraphyletic)
Ahaetulla prasina (paraphyletic) Ahaetulla mycterizans
Ahaetulla prasina (paraphyletic)
Ahaetulla mycterizans
Ahaetulla prasina (paraphyletic)
Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic) Ahaetulla fronticincta
Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic) Ahaetulla nasuta (paraphyletic)
Ahaetulla anomala Ahaetulla pulverulenta Ahaetulla nasuta (paraphyletic)
Ahaetulla anomala Ahaetulla pulverulenta
Ahaetulla anomala
Ahaetulla pulverulenta
Ahaetulla nasuta (paraphyletic)
Ahaetulla nasuta (paraphyletic)
Ahaetulla fronticincta
Proahaetulla antiqua
DryophiopsDryophiops rubescens Dryophiops philippina
Dryophiops rubescens
Dryophiops philippina
broad‑nosed snakesDendrelaphis Dendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus Dendrelaphis formosus Dendrelaphis tristis Dendrelaphis subocularis Dendrelaphis schokari Dendrelaphis fuliginosus Dendrelaphis caudolineatus Chrysopelea Chrysopelea paradisi Chrysopelea ornata Chrysopelea pelias Chrysopelea taprobanica
DendrelaphisDendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus Dendrelaphis formosus Dendrelaphis tristis Dendrelaphis subocularis Dendrelaphis schokari Dendrelaphis fuliginosus Dendrelaphis caudolineatus
Dendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus Dendrelaphis formosus
Dendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus
Dendrelaphis marenae Dendrelaphis haasi Dendrelaphis pictus
Dendrelaphis marenae Dendrelaphis haasi
Dendrelaphis marenae
Dendrelaphis haasi
Dendrelaphis pictus
Dendrelaphis ngansonensis Dendrelaphis cyanochloris Dendrelaphis striatus
Dendrelaphis ngansonensis Dendrelaphis cyanochloris
Dendrelaphis ngansonensis
Dendrelaphis cyanochloris
Dendrelaphis striatus
Dendrelaphis formosus
Dendrelaphis tristis Dendrelaphis subocularis Dendrelaphis schokari Dendrelaphis fuliginosus Dendrelaphis caudolineatus
Dendrelaphis tristis Dendrelaphis subocularis Dendrelaphis schokari
Dendrelaphis tristis Dendrelaphis subocularis
Dendrelaphis tristis
Dendrelaphis subocularis
Dendrelaphis schokari
Dendrelaphis fuliginosus Dendrelaphis caudolineatus
Dendrelaphis fuliginosus
Dendrelaphis caudolineatus
ChrysopeleaChrysopelea paradisi Chrysopelea ornata Chrysopelea pelias Chrysopelea taprobanica
Chrysopelea paradisi Chrysopelea ornata Chrysopelea pelias
Chrysopelea paradisi Chrysopelea ornata
Chrysopelea paradisi
Chrysopelea ornata
Chrysopelea pelias
Chrysopelea taprobanica

Description

Proahaetulla antiqua is bright green, with a lighter green or creamish yellow belly, and a creamish yellow ventral stripe. The holotype had a total body length of 111.3 cm (43.8 in), with a very slender and partially laterally compressed body. It has a fine-pointed snout and near-binocular vision, with horizontally elliptical pupils in its eyes. It is very similar in appearance to Ahaetulla dispar.

Distribution and habitat

It is a diurnal and arboreal species found in the high elevation rainforests of the far south of the Western Ghats.