Underwoodisaurus is a small genus of Australian lizards in the family Carphodactylidae. Member species are commonly known as thick-tailed geckos, along with the species Uvidicolus sphyrurus.
The genus Underwoodisaurus has a complex taxonomic history, but the currently accepted taxonomic concept follows Oliver & Bauer (2011),[2] with a second species subsequently recognised by Doughty & Oliver (2011).[3] Reptile systematists nowadays recognise a distinct family, Carphodactylidae, for this and some related genera.[4]
Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Underwoodisaurus. The species Uvidicolus sphyrurus is sometimes placed in the genus Underwoodisaurus.
Adults of some species of Underwoodisaurus can reach a snout-to-vent length (SVL) of 80 mm (3.1 in). Preanal pores are absent. The feet are generally "bird-like" with long slender digits, and the tail is carrot-shaped. The underside of the body is white, and the dorsal surface ranges from dark purplish-black through reddish-brown to pale fawn, with small white, yellow and black spots in patterns.[5]
A thick tail is generally a sign of good health, although lack of thickness may indicate recent egg-laying.
The genus Underwoodisaurus is endemic to Australia. These geckoes are found in a range of habitats including wet coastal heathlands, wet sclerophyll forests, arid scrubland, rocky outcrops and stony hills in eucalypt woodland.[5]