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Underwoodisaurus milii.jpg
Thick-tailed gecko (Underwoodisaurus milii)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Carphodactylidae
Genus: Underwoodisaurus
Wermuth, 1965

Two recognized species, see text.

Underwoodisaurus is a small genus of Australian geckos, commonly known with the species Uvidicolus sphyrurus as thick-tailed geckos. The species Underwoodisaurus milii is often called the thick-tailed gecko.


The generic name, Underwoodisaurus, is in honor of British herpetologist Garth Leon Underwood.


The genus Underwoodisaurus has a complex taxonomic history, but the currently accepted taxonomic concept follows Oliver & Bauer (2011), with a second species subsequently recognised by Doughty & Oliver (2011). Reptile systematists nowadays recognise a distinct family, Carphodactylidae, for this and some related genera.


There are two recognised species:

  • Underwoodisaurus milii (Bory de Saint-Vincent, 1825) – thick-tailed gecko
  • Underwoodisaurus seorsus Doughty & P. Oliver, 2011

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 can reach a snout-to-vent length of 80mm. 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.

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.


Thick-tailed geckos shelter under leaf litter, around the bases of trees in loose bark, and in crevices.

They emerge in the evenings to hunt in open areas for crickets, cockroaches and huntsman spiders. They eat once every 3–4 days. When they see prey they will stare at it and wag their tails, then pounce. When alarmed, the thick-tailed gecko will make a barking sound or hiss. They will also raise their backs. One main predator is snakes.


Thick-tailed geckos lay up to 2 eggs and up to 10 clutches per year. The first clutch of eggs is usually infertile. When the female is gravid the eggs are visible through the skin. The eggs take about 65 days to hatch. Their breeding season is roughly July to February.

  • Cogger HG (2014). Reptiles and Amphibians of Australia, Seventh Edition. Clayton, Victoria, Australia: CSIRO Publishing. xxx + 1,033 pp. . (Underwoodisaurus, pp. 283-284).
  • Wermuth H (1965). "Liste der rezenten Amphibien und Reptilien, Gekkonidae, Pygopodidae, Xantusiidae ". Das Tierreich 80: 1-246. (Uderwoodisaurus, new genus). (in German).
  • Wilson, Steve; Swan, Gerry (2013). A Complete Guide to Reptiles of Australia, Fourth Edition. Sydney: New Holland Publishers. 522 pp. .
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