Cartilage an Embryonic Adaptation

Abstract

A review of the oldest fossil forms strongly indicates that, contrary to current beliefs, bone rather than cartilage was the skeletal material characteristic of the adult stage in primitive vertebrates. This conclusion is not necessarily in disagreement with the embryonic history of skeletal tissues for it is impossible to conceive of a method of development of internal skeletal elements with bone present throughout. Cartilage presumably arose early in vertebrate history as an embryonic adaptation to . permit of ready growth and changes of form antecedent to a definitive adult bony condition. The presence of cartilage in an adult modern vertebrate is to be regarded as a degenerate, neotenic condition.