The Development of the Chondrocranium of Typhlonectes compressicaudus (Gymnophiona), with Comparison to Other Species

The development and degeneration of the chondrocranium of Typhlonectes com- pressicaudus (Typhlonectidae: Gymnophiona: Amphibia) is described and compared with data for other gymnophione species. The typhlonectid pattern exemplifies many of the constraints typical of gymnophiones (emphasis on otic and nasal capsule development, late development of stapes, retention of cartilaginous nasal capsule rims), but has a number of unique features as well, espe- cially extensive lateral vaulting of the braincase, the absence of a cartilaginous mesethmoid com- ponent and its precursors, and concomitant modifications of nasal capsule development. Other aspects of development are apparently correlated with both the live-bearing mode (early mineral- ization of tooth crowns and jaw articulation surfaces) and with the aquatic habits of the species (reduced overlap of dermal elements).