EVOLUTIONARY DIVERSIFICATION OF CRANIAL AND SPINAL NERVES AND THEIR TARGETS IN THE GYMNOPHIONE AMPHIBIANS

The ancestral gymnophione (caecilian) became elongate and limbless ear ly in its history. Further structural reduction, including loss of com ponents, followed by redirection and occasionally cooption of remainin g structures, particularly muscles and nerves, has evolved. Function m ay remain that of the ancestral condition, or may change dramatically. Examples include the evolution of the tentacle, the jaw-closing appar atus, and the hypobranchial musculature, including their innervation. 'Regressive' evolution has provided opportunity for new structural-fun ctional relationships and for increased variation.