| Comparison of homologous bones of the forelimbs (pectoral appendages or arms) of a lobe-finned fish from central Pennsylvania (left) with an amphibian like tetrapod from Greenland (right). Both are right limbs seen from the underside. H=upper arm bone or humerus; U and r=forearm bones or ulna and radius; u and i=wrist bones or ulnare and inter- medium. The hand and finger bones are dark. (Modified from Daeschler and Shubin, 1998) |