An Early Jurassic caecilian with limbs

Abstract

CAECILIANS are elongate, limbless, mostly fossorial amphibians. Less well known than frogs and salamanders, they are represented today by about 34 genera and 162 species¹. Until recently, the fossil record of caecilians consisted of only two vertebrae, one from the Palaeocene of Brazil², the other from the Late Cretaceous of Bolivia³. We report here the discovery of an extensive series of Early Jurassic caecilians which extends the fossil record of the group and reveals numerous features, including limbs, that are unknown among modern species. Although the new taxon possesses a tentacular fossa for a chemosensory organ and specializations of the jaw apparatus that are uniquely caecilian, other derived features are shared with salamanders and, among extinct Palaeozoic forms, with microsaurs. The configuration of the skull roof, which differs from the fenestrated condition typical of frogs, salamanders and putatively primitive living caecilians, is evidence of substantial evolutionary divergence between caecilians and other modern amphibian groups.