Dibamidae

Dibamidae or blind skinks is a family of lizards characterized by their elongated cylindrical body and an apparent lack of limbs. Female dibamids are entirely limbless and the males retain small flap-like hind limbs, which they use to grip their partner during mating. They have a rigidly fused skull, lack pterygoid teeth and external ears. Their eyes are greatly reduced, and covered with a scale. Blind skinks are native to Mexico, Southeast Asia, Indonesia, the Philippine Islands, and western New Guinea. They are small insectivorous lizards, with long, slender bodies, adapted for burrowing into the soil. They usually lay one egg with a hard, calcified shell, rather than the leathery shells typical of many other reptile groups. The family Dibamidae has two genera, Dibamus with 23 species and the monotypic Anelytropsis. Recent phylogenetic analysis places the dibamids as the sister clade to all the other lizards and snakes. Dibamids are burrower lizards characterized by their elongated bodies with blunt head and tail, and an apparent lack of limbs. Relatively small, blind skinks can reach a maximum length of 250 mm (9.8 in) from head to tail and the snout vent length (SVL) is variable between both genus Anelytropsis and Dibamus. In Anelytropsis, the tail is longer than in Dibamus and represents between 34 to the 38% of the snout vent length which can range from 77 to 180 mm (3 to 7 in). In Dibamus, the tail corresponds to 9 to 25% of the SVL that varies from 52 to 203 mm (2 to 8 in). Usually dibamids are dark colored, from brown to dark purple, with little to none variation along their body and frequently lack elaborate patterns. It is common to find a color degradation from the darker back towards a lighter ventral side. Scales are shiny and smooth and very similar and overlapping along with some variation in number and shape in the head and anal regions where males usually have additional scales to cover anal pores. Scale row counts varies between both genera; Anelytropsis has 19 to 25 rows whereas Dibamus has 18 to 33. In both groups osteoderms are absent. General characteristics of the soft tissue includes a tongue that is covered in lamellae except in the tip, heavily modified ears without external openings or middle ear cavity or eustachian tubes, and highly reduced eyes that lack internal structure and are covered by a scale and lack internal structure, particularly in Dibamus. Dibamids are lizards with highly reduced limbs but they are not completely limbless. Males and females have rudimentary poorly developed hind limbs containing a femur, tibia and fibula in males, and distal cartilage cap, this elements are more developed on Dibamus than in Anelytropsis. Female dibamus lack the tibia and the fibula. The skull is approximately 5 - 7 mm in length with reduced kynesis and a more rigid skull for burrowing. The combination of fossorial habits and small size, contributes to the development of a skull configuration that is frequently found in other groups of burrowers and miniaturized species. Among those characteristics are the closure of the supratemporal fenestra and the post-temporal fenestra, the relative large braincase, tubular or scroll-like palatines and modified jaw suspension mechanism with the quadrate articulating with the lateral wall of the braincase.