The Uropeltidae, also commonly known as shield-tail snakes, shield-tailed snakes or earth snakes,[2] are a family of primitive, nonvenomous, burrowing snakes native to Peninsular India and Sri Lanka. The name is derived from the Greek words ura ('tail') and pelte ('shield'), indicating the presence of the large keratinous shield at the tip of the tail. Seven or eight genera are recognized, depending on whether Teretrurus rhodogaster is treated in its own genus or as part of Brachyophidium.[2][3] The family comprises over 50 species.[2] These snakes are not well known in terms of their diversity, biology, and natural history.
Description
Tails of Uropeltidae
Snakes in the family Uropeltidae are small snakes, with adults growing to a total length (including tail) of 20–75 cm (7.9–29.5 in). 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.[4]
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.[4] The body is cylindrical and covered with smooth scales.
Behaviour and natural history
Many species of shield-tail 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.[5]
Geographic range
Shield-tail snakes are found in Peninsular India and Sri Lanka.[1] In India, their distribution is mainly along the hills of the Western Ghats, and a few species occur in other areas such as the Eastern Ghats and the 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 each having an endemic shield-tail snake, they are thought to be analogous to Darwin's finches, in a broader sense – an evolutionary radiation.[6] 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.[7][8][9] Molecular dating analysis has suggested that uropeltids originated around the Paleocene-Eocene boundary, splitting from its sister clade Cylindrophiidae + Anomochilidae around 56 MYA.[9]
Feeding
The diets of shield-tail snakes 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 the family Uropeltidae retain eggs that hatch within the body of the mother (ovoviviparity).[10]
^ abParker HW, Grandison AGC (1977). Snakes – a Natural History, Second Edition. London and Ithaca: British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN0-8014-1095-9 (cloth), ISBN0-8014-9164-9 (paper).
^Rajendran MV (1985). Studies in Uropeltid Snakes. Madurai: Madurai University Press.
^Ganesh SR (2015). "Shieldtail snakes (Reptilia: Uropeltidae) – the Darwin's finches of south Indian snake fauna?" pp. 13–24. In: Manual on Identification and Preparation of Keys of Snakes with Special Reference to their Venomous Nature in India. Ooty: Government Arts College.
^Tinkle DW, Gibbons JW (1977). "The Distribution and Evolution of Viviparity in Reptiles". University of Michigan Museum of Zoology, Miscellaneous Publications (154): 1–55. PDF
Das I (2002). A Photographic Guide to Snakes and other Reptiles of India. Sanibel Island, Florida: Ralph Curtis Books. 144 pp. ISBN0-88359-056-5. (Uropeltidae, p. 59).
Goin CJ, Goin OB, Zug GR (1978). Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman and Company. xi + 378 pp. ISBN0-7167-0020-4. (Uropeltidae, pp. 197, 309, 320).
