Physical characteristics

The bodies of xenosaurids are relatively unique, at least compared to the more common lizards, such as Sceloporus and Anolis, of Central America and Mexico. In fact, the name Xenosaurus means "alien lizard." Compared to more typical lizards, xenosaurids have a flattened body and a flat, somewhat triangular head. Presumably the flattened body shape is related to the crevice- or hole-dwelling habit of these lizards.

The flattened head of these crevice-dwellers may influence how hard they can bite. Anthony Herrel and his colleagues found that xenosaurids with taller heads were able to bite more strongly than those with shorter heads. It is not clear whether the reduced bite strength of these flat-headed lizards is important ecologically because the jaws are still strong enough to easily crush their arthropod prey.

Male and female Xenosaurus often differ in body and head size, although the extent of sexual dimorphism varies between species. In most cases, females are bigger than males (e.g., X. newmanorum, X. platyceps), but no difference has been seen in some (e.g., X. grandis grandis, X. rectocollaris). While

A knob-scaled lizard (Xenosaurus platyceps). (Photo by Laurie J. Vitt. Reproduced by permission.)

females are often bigger in body size, males typically have larger heads, perhaps related to aggression between males.

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