A Huge Group

This cladogram maps evolutionary relationships among the squamates. The word squamate comes from the Latin squama, meaning scale, and scales are one thing all squamates have in common.

Scientists recognize many groups of living squamates. Some groups include many species and some only a few; some names are familiar, some aren't. The cladogram includes snakes, because snakes are one kind of legless lizard, but scientists still don't know exactly where snakes belong in the tree. Are they closest to Gila Monsters and their relatives? Skinks and their relatives? Ideas differ.

Reconstructing evolutionary history is a continuing process, and this cladogram shows one current view of that history. New evidence may change it, or confirm it. In this exhibit, closely related groups are shown near one another.

A Diagram of Life

This diagram is called a cladogram (CLAY-doh-gram), from the Greek word meaning "branch." A clade is a group of animals with a common ancestry; groups on the same branch are more closely related than groups on different branches.