homologous

In his famous discussion of the panda's thumb, Stephen Jay Gould carefully explains how this thumb is not homologous to the human thumb. Although the two digits are used in much the same way (the panda's thumb is essential for stripping bamboo of its tasty leaves, the staple of the panda's diet), the panda's thumb developed from a bone in its wrist and is an addition to the five "fingers" of its paw. The tiny stirrup and anvil bones of our inner ear, however, do seem to be homologous with the bones that allow a garter snake to swallow a frog whole.