Order Squamata

~74 species of lizards, 91 snakes in US, none in Alaska
lizards distinguished from snakes by moveable eyelids; glass lizards also distinguished from snakes by circular scale pattern (snakes elliptical) and external ear opening
smaller lizards 1st order insectivores, larger may be herbivorous; all snakes predaceous

Members of the Squamata order particularly are known to all possess movable quadrate bones, making it possible to move the upper jaw relative to the braincase. This is particularly visible in snakes, which are able to open their mouths very widely to accommodate comparatively large prey. Other shared traits include having only a single temporal opening or it is lost or reduced, a highly modified skull, and with the male members of the group Squamata being the only vertebrates with a hemipenis (possessing paired penes). They also are distinguished by their skins, which bear horny scales or shields, while lacking any shells or secondary palates. This is also the only reptile group in which can be found both viviparous and ovoviviparous species, as well as the usual oviparous reptiles.

snakes and lizards