Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

Squamata




Karoo sand snake (Psammophis notostictus)
An order of cold-blooded scaly reptiles, comprising the snakes (suborder Serpentes) and lizards (suborder Lacertilia). They are mostly terrestrial vertebrates that first appeared at the end of the Triassic period, about 170 million years ago.

Typically, lizards have cylindrical bodies with four legs, a long tail, movable eyelids. Snakes are legless reptiles with no external ear openings, eardrums, or middle ears; sound vibrations are detected through the ground. Their eyelids are immovable. The long, forked, protractile tongue is used to detect odors. Poisonous species have hollow or grooved fangs, through which they inject venom.


Related category

   • ZOOLOGY