Australian Water Dragon - The Australian Museum

Identification

The genus Physignathus was described by George Cuvier (1769-1832) in 1829 based on the type specimen of the genus; the Green Water Dragon, Physignathus cocincinus of south-east Asia. The name Physignathus translates to "puff-cheek" and refers to the bulging appearance of the throat and lower jaw. Physignathus comprises two recognised species; Physignathus lesueurii and Physignathus concincinus. The specific name lesueurii honours the French naturalist Charles-Alexandre Lesueur (1778-1846) who collected this species on the Baudin expedition of 1800. There are two recognised subspecies of Water Dragon; the Eastern Water Dragon, Physignathus lesueurii lesueurii and the Gippsland Water Dragon, Physignathus lesueurii howittii. A recent taxonomic review concluded that the Australian species of Physignathus shows enough differing characteristics to classify it in its own genus, since Physignathus was first assigned to P. cocincinus, a new genus hand to be created for the Australian Water Dragons. In 2012 the species was officially renamed Intellagama lesueurii.

The Water Dragon can be identified by a distinctively deep angular head and nuchal crest of spinose scales that joins the vertebral crest extending down the length of its body to the tail. Enlarged spinose scales are also present across the lateral surface, unevenly distributed amongst regular keeled scales. The jowls are large and ear is exposed and of almost equal size of the eye. The dorsal ridge and tail are laterally compressed and the limbs are strong and robust with particularly long toes on the hind legs. The tail is capable of regeneration when lost, furthermore, regenerated tails can also grow back when severed.

Colouration differs between the subspecies; the Eastern Water Dragon, Intellagama lesueurii lesueurii, has a grey to brownish-grey colour above with patterns of black stripes along the dorsal ridge as well as down the tail. There is also a dark stripe horizontally from the eye back over the tympanum and extending down the neck. The limbs are mostly black with spots and stripes of grey and the tail is patterned with grey and black stripes. The ventral surface is yellowish-brown, with the chest and upper belly becoming bright red in mature males.

The Gippsland Water Dragon, Intellagama lesueurii howittii, is identical in morphology apart from slightly smaller spinose scales but differs in colouration and patterning. Dorsally the body is olive-green to brown in colour with transverse black stripes. The dark stripe from the eye to ear is absent. Mature males have dark blue-green chests and streaks of yellow and blue around the neck and throat.