STUDIES ON SKELETON FORMATION IN REPTILES - PATTERNS OF OSSIFICATION IN THE SKELETON OF CHELYDRA-SERPENTINA (REPTILIA, TESTUDINES)

Patterns and sequence of ossification are described throughout the ske leton of Chelydra serpentina Linnaeus. Evidence is adduced documenting the decoupling of ossification processes from sequence and patterns o f chondrification. Convergence of ontogenetic repatterning in the ossi fication of the axial skeleton in Chelydra and Squamata is discussed, as are problems of adaptive modification of ossification patterns. The development of a carapace may be correlated with changes of ossificat ion patterns in the postcranial axial skeleton of turtles, but the mos t striking evidence for the adaptive modification of ossification sequ ence obtains from a comparison of the limb skeleton and its ossificati on in Chelydra and in sea turtles.