The first Pterosaurs appear suddenly on the scene during the Late Triassic. These Rhamphorhynchoids are fully developed with a fully modified skeleton for flight. An intermediate stage between terrestrial reptile and Pterosaur has yet been found. It is highly unlikely that the "missing link" will ever be found (if one ever existed).

The way paleontologists determine ancestors is to compare features among groups. Characteristics are chosen which seem best to define the group and then these characteristics are analyzed by being weighted against other characteristics from other groups. This technique is termed cladistics.

Some of the more important characteristics in pterosaurs include: a proportionately large skull, three sacral vertebrae, broad sternum formed of paired clavicles, elongated forelimb, pteroid bone, and a greatly elongated fourth digit (There are many other characteristics that are chosen).



© Patrick Lyons 1998.