Uropeltidae

Description

These are small snakes, with adults growing to between 20 and 75 cm in length. They are adapted to a fossorial way of life, which is apparent in their anatomy. The skull is primitive and inflexible, with a short, vertical quadrate bone and rigid jaws; the coronoid bone is still present in the lower jaw. The orbital bones are absent, the supratemporal is vestigial and the eyes are small and degenerate, not covered by a brille, but by large polygonal shields. However, the pelvis and hind limbs, the presence of which is also considered a primitive trait, have disappeared in this family.

The tail is characteristic, ending in either an enlarged rigid scale with two points, or more often an upper surface with a subcircular area covered with thickened spiny scales, or a much enlarged spiny plate. The ventral scales are much reduced in size. The body is cylindrical and covered with smooth scales.

Behaviour and natural history

Many species of shieldtail snakes are rather poorly known in terms of natural history. Field studies indicate that most species are obligate burrowers and may often come out on to soil surface during rainy nights. Even roadkills of these snakes have been recorded by field biologists during peak monsoon rains. They seem to prefer the humus-rich topsoil layers and rarely burrow deeper inside (like during very hot or dry weather).

When approached by predators, these snakes do not bite like most snakes, but coil their bodies into a ball and hide their heads tucked underneath. Some may poke with their harmless tail tip, like a worm snake. Many have a drab and dull-coloured back, but a very bright, contrastingly coloured underside (such as bright yellow, red, etc.) to startle predators by turning upside down and twitching. This aposematic colouration wards off would-be predators.

Geographic range

They are found in peninsular India and Sri Lanka. In India, their distribution is mainly along the hills of Western Ghats, and a few species occur in other areas such as the Eastern Ghats and hills of Central India. In Sri Lanka, they occur in many biotopes including dry zone and the plains.

Evolutionary significance

Because of their peculiar geographic distribution, with many hill ranges in South India and Sri Lanka having an endemic shieldtail, they are thought to be analogous to Darwin's finches, in a broader sense - an evolutionary radiation. This is the only family of snakes endemic to South Asia. Genetic studies on this group have brought forth largely similar results as regards common ancestry and phenotypic diversification patterns.

Feeding

Their diets consist mostly of invertebrates, particularly earthworms, and many species have actually been observed in the wild by researchers to eat earthworms. Frank Wall, who dissected many species for analysing the gut contents to study the diet, remarks about the presence of worms and mud.

Reproduction

All members of this family retain eggs that hatch within the body of the mother (ovoviviparity).

Genera

^T) Type genus