Crotaphytidae

The Crotaphytidae, commonly referred to as collared lizards, represent a family of reptiles adapted to arid environments. These lizards are native to the desert regions of the southwestern United States and northern Mexico. They are distinguished by their remarkable speed, facilitated by long limbs and tails, with some species exhibiting the ability to run on their hind legs at high velocities.

Physical Characteristics and Behavior

Collared lizards possess several key physical traits that aid their survival in desert habitats. These include long limbs, long tails, and the capacity for bipedal locomotion. Technically, they are characterized by the presence of femoral pores and a small interparietal scale, distinctly smaller than their ear opening. Unlike some other lizard groups, they do not have an enlarged middorsal scale row or fringe, nor a divided rostral scale. They also lack bony spines or projecting ridges on their heads, and their ears are not covered by projecting scales. Additionally, they lack the prominent toe fringe seen in some related families.

Diet and Ecology

The diet of Crotaphytidae is primarily carnivorous, consisting of insects and smaller lizards. Their swift movements are crucial for both hunting their prey and evading potential predators. The family is composed of two genera, which together encompass 12 distinct species.

Taxonomy and Relatives

While recognized as a family, Crotaphytidae is sometimes classified as a subfamily, Crotaphytinae, within the clade Pleurodonta. There is also a potential evolutionary link suggested between Crotaphytidae and the extinct Arretosauridae of Paleogene Asia, based on similarities in jaw morphology. However, other studies place Arretosauridae within Acrodonta, grouping them with Old World iguanians.