Family Scincidae (Skinks)

Order Squamata
Suborder Scincomorph

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Family Scincidae (Skinks)

The family Scincidae is the most species-rich lizard family with about 1200 species. Many species-rich genera (e.g. Sphenomorphus, Mabuya) are still studied insufficiently and their systematics is controversial.

Appearance: Typically scincids are slighly to markedly elongate lizards that have relatively long-snouted and somewhat flattened skulls, in which the upper temporal opening is usually reduced or lost. The head is usually covered with enlarged plates, termed head shields, and osteoderms are frequently present in some or all scales. These osteoderms are unusual because each is composed of a set of smaller ones in contrast to a single bone as in other lizards. Smooth, shiny cycloid scales (few exceptions, e.g. members of the genus Tribolonotus). The partially to well-developed secondary palate is a distinctive feature of the skull. It is formed primarily by development of a novel lamina of the palatine bone on each side, which together essentially floor and prolong the choanal passage. In some species the palatal rami of the pterygoids extend the secondary palate posteriorly to about the level of the back of the tongue. Other osteological characteristics include paired premaxillae, descending processes from the parietals which meet the epipterygoids and an enlarged coronoid process of the dentary. The inner ear has an accessory inertial body, the culmen, which modulates hair cell sensitivity, and largely replaces the tectorial membrane, which is vestigial in skinks. Preanal and femoral pores are absent.

Limb loss: Several lineages of skinks have lost their limbs completely (e.g. Brachymeles, Isopachys, Typhlosaurus, Acontias). A few genera have species with various degrees of limb loss (e.g. Lerista and Chalcides, see Greer 1987). The tail is usually long and tapering and, except for a very few species, can be shed and regenerated. The tongue is broad, has an arrowhead-shaped tip and is covered with serrated scales. Limb reduction in some form has occurred more than 30 times within skinks (Greer, 1991). Several authors have argued that there may have been a reversal of limb loss in a few lineages of skinks but this has not been demonstrated convincingly (see discussion in Greer 1991 and Ehiting et al. 2003).

Zoological definition: (1) ossifications present in eyelids; (2) osteoderms present dorsally, ventrally, and on head; (3) upper arcade complete or nearly, with jugal and squamosal near or in contact; (4) upper temporal fossa roofed over, mainly by postfrontal; (5) no femoral or pre-anal pores; (6) dorsal scales flat and imbricate

Distribution: Worldwide

Habitat: Terrestrial and fossorial species are more prevalent than arboreal (e.g. Corucia) or aquatic species (e.g. Tropidophorus, Amphiglossus astrolabi). Many species in desert regions are sand swimmers. divergent paths.W hereas Ctenotus is primarily heliothermic (except for C. pantherinus) and surface dwelling (Greer, 1989), Lerista is primarily a fossorial group with the majority of the species exhibiting some level of limb reduction (Greer, 1987, 1990).

Size: Small- to moderate-sized (approximately 80% are 30-120 mm SVL maximum). A few skinks are larger, for example, Tiliqua is 9&emdash;31 cm SVL and Corucia is 35 cm SVL.

Food: Usually carnivorous.

Behaviour: Mostly diurnal; some are nocturnal or crepuscular. Egernia is the most sociable lizard known: 23 of the 31 species in the genus live in some form of family group (O'Connor & Shine 2003: Mol. Ecol. 12: 743, Chapple 2003 Herp. Monogr. 17: 145).

Reproduction: About 45% of skinks are viviparous. Eggs are laid as single clutches (guarded or abandoned) or, infrequently, communally. Clutch size is commonly low (~ six) and is limited to one or two eggs in some species groups (e.g., Tribolonotus and Emoia, respectively).