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a family of amphibians of the order Caudata. The body is long and cylindrical and lacks hind legs. The external gills remain throughout the animal’s life. The eyes are small and lidless. There are horny plates instead of maxillary bones.
Modern species of Sirenidae seem to be neotenic forms that lost their capacity for metamorphosis as a result of secondary adaptation to an aquatic mode of life. There are three species belonging to the two genera Siren and Pseudobranchus. The Sirenidae occur in the northeastern part of North America. The most common species, S. lacertina, is up to 70 cm long and has four-digited limbs and three pairs of gill slits. The amphibian is dark brown above but lighter below. It inhabits bogs and the shores of heavily overgrown bodies of water; it feeds on invertebrates and small fishes.