affinities

The reptilian elements of Sri Lanka show Indo-Malayan (21 genera), Afro-Mediterranean (six genera), Filippino (one genus) and probably Madagascan ( ? genera ) links. But despite the small size, Sri Lanka possesses a much higher number of endemic and relict fauna than mainland India. The relict (an organism that at an earlier time was abundant in a large area but is now occurring at only one or a few small areas. Usually theses are endemic to an area at genus or higher taxonomic level) reptile genera in the country comprises genus Pseudotyphlops of family Uropeltidae; genera Aspidura, Balanophis, Cercaspis, Haplocercus of family Colubridae; genera Ceratophora, Cophotis, Lyriocephalus of family Agamidae and genera Nessia, Lankascincus, Chalcidoceps of family Scincidae.

The Indian subcontinent and the Malayan region have been divided into zoogeographical regions or sub-regions based on criteria such as topography, climate and the vegetation formation. Several authors have grouped Sri Lanka in different zoogeographical groupings, as,

Mahendra (1984) - considered the island to be a distinct zoogeographical province

Blanford (1901) - grouped the Indian peninsula and Sri Lanka as one sub-region called Cis-Gangetic sub-region

Smith (1931) - considered Sri Lanka and the montane zone of the Malabar track of South India to be a single region.

Sri Lanka and the Indian peninsula together constitute the tectonic structure known as the Deccan plate and as Sri Lanka was a geological extension of the southern tip of the Indian peninsula till the Miocene period, a majority of the reptiles in the country have affinities with the Indian sub-continent. The subsequent land connections which have occurred several times have also helped in the spread of ancestral stocks from mainland India to Sri Lanka. Based on the number of endemics in each group, Family Uropeltidae, Typhlophidae and the genus Aspidura of Colubridae are considered to be early arrivals in the country while species such as Argyrogena fasciolata, Gerardia prevostinia etc. are considered late arrivals, as they are only known from very few specimens.

Some snake genera such as Cylindrophis , Dendrelaphis , Chrysopelea, Dryocalamus, Atretium, Boiga, Ahaetula and the agamid genus Cophotis are considered to have distinct Malayan affinities. Similarly the sea snakes of the Family Hydrophiidae are assumed to be derived from an Autralasian elapid radiation and to have traveled along the coasts of Thailand and Burma.

Certain of the elements of the fauna of the island are similar to that of Madagascar, including Sibynophis, which is found on both these islands and in mainland India, but not in Africa. Also the endemic Sri Lankan scincid genus Nessia appears very close to the Madagascan scincid genus Acontias in morphology, thus is considered to have Madagascan affinities.