AN EARLY JURASSIC CAECILIAN WITH LIMBS

CAECILIANS are elongate, limbless, mostly fossorial amphibians. Less w ell known than frogs and salamanders, they are represented today by ab out 34 genera and 162 species1. Until recently, the fossil record of c aecilians consisted of only two vertebrae, one from the Palaeocene of Brazil2, the other from the Late Cretaceous of Bolivia3. We report her e the discovery of an extensive series of Early Jurassic caecilians wh ich extends the fossil record of the group and reveals numerous featur es, including limbs, that are unknown among modern species. Although t he new taxon possesses a tentacular fossa for a chemosensory organ and specializations of the jaw apparatus that are uniquely caecilian, oth er derived features are shared with salamanders and, among extinct Pal aeozoic forms, with microsaurs. The configuration of the skull roof, w hich differs from the fenestrated condition typical of frogs, salamand ers and putatively primitive living caecilians, is evidence of substan tial evolutionary divergence between caecilians and other modern amphi bian groups.