Friday, April 8, 2016

Chacachacare Shiny Lizard, Gymnophthalmus sp. (Family Gymnophthalmidae)

Size: 40 mm SVL, tail about 1.7x SVL. The dorsum is shiny bronze-brown with pale dorsolateral lines extending from the snout to base of the tail. Lateral scales only slightly smaller than dorsals. Ventral scales 23–27. G. underwoodii has 21–24 ventrals, and a dorsolateral stripe that fades at mid body. G. sp. is a bisexual species.  Both species of Gymnophthalmus have well developed limbs with four fingers and five toes. Both species of skinks have imbricate, cycloid scales and well developed limbs with five fingers and five toes. Distribution: In the broadest sense this group of cryptic species ranges from Mexico through Central America into Colombia, Venezuela, Guyana, and Brazil.  Habitat: Inhabits open, sunny areas on lawns and at the forest edge, seems to prefer habitats without leaves. Most often seen in bright sunlight. Biology. Diurnal. Diet has not been studied, but it most likely feeds on insects and other arthropods.  Reproduction: Both sexes present in the population. Gymnophthalmus contains a cluster of cryptic species, species that look similar to each other but are genetically distinct. Two of these species are known from Trinidad, Tobago, and their satellites. Gymnophthalmus speciosus (or lizards that look like it) is widespread in Venezuela, as well as Chacachacare Island in the Bocas. A second species, G. cryptus occurs in western Venezuela and the middle Rio Orinoco drainage system. And, a third species, G. underwoodii occurs in Trinidad, Guyana, Suriname, French Guiana, northern Brazil, and the West Indies as far north as Antigua. Gymnophthalmus cryptus is not morphologically distinct from G. sp., but they are genetically distinct. The third species G. underwoodii is an asexual clone formed by the hybridization of G. cryptus and G. sp. The clone species probably originated in the middle Orinoco drainage and dispersed downstream during flooding. It was then able to colonize Trinidad and the islands to the north as well as coastal Guyana. 

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