A new genus of lungless tetrapod: a radically divergent caecilian (Amphibia: Gymnophiona)

Abstract

Lunglessness is rare in the Tetrapoda and previously recorded only in salamanders (Amphibia: Caudata). Here we report lunglessness in another group of tetrapods, the poorly known tropical caecilians (Amphibia: Gymnophiona). Typhlonectes eiselti is a lungless, aquatic caecilian from South America known only from the single holotype specimen, NMW 9144 (Vienna Museum of Natural History). At a total length of 725 mm, NMW 9144 is by far the largest known lungless tetrapod. It also has a startling array of other radically divergent morphological features, many unique, and some correlated with lunglessness including: sealed choanae (paired internal nostrils); complete absence of pulmonary blood vessels; a repatterned skull with post-occipital jaw articulation; and a novel cranial muscle associated with an elongate and redirected stapes. This remarkable combination of highly derived characters sets Typhlonectes eiselti apart from all other caecilians and places it on a novel evolutionary trajectory. A new genus is described to accommodate this form.