Uromastyx hardwickii, Indian Spiny-tailed Lizard skull

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The spiny-tailed lizard, Uromastyx, is traditionally placed in the iguanian group Agamidae, although -- with Leiolepis -- it is generally acknowledged to be a basal taxon. Uromastyx is a desert lizard found in both rocky and sandy terrains from North Africa (Morocco to Mauritania, across to Egypt and the Sudan) and the Middle East (the Arabian Peninsula, Iran, Iraq) to India, Afghanistan and Pakistan. Some 13 species are currently recognised, of which U. aegyptis (Egypt), U. acanthinurus (Morocco), and U. hardwickii (India, Pakistan) may be among the more familiar. The fossil record is not extensive but Uromastyx has been reported from the Eocene of Europe (Auge, 1988), demonstrating a more extensive original range. Uromastyx hardwickii Adults vary in size, but can reach at least half a metre in total length. They create large spiral burrows using powerful claws. Uromastyx is omnivorous, but while the young feed predominantly on invertebrates, adults incorporate a high degree of plant material into their diet. The skull of Uromastyx shows the following features typical of agamid lizards: reduced single premaxilla; strong anterior maxillary contact behind the premaxilla; single frontal and parietal with wide frontoparietal suture; strong preorbital pillar (prefrontal-palatine contact); palate palaeochoanate (i.e. without separation of the vomeronasal opening from the choana); and braincase exposed in dorsal view. Siebenrock (1895) recognised two major skull types amongst agamids: the first, laterally compressed, is found mostly in arboreal genera; the second, wider and flattened, occurs mainly in terrestrial taxa like Uromastyx.