text: mud puppy, common name for North American salamanders of the genus Necturus, found in rivers and streams throughout the E United States and SE Canada. The name derives from an erroneous belief that mud puppies bark. Like its relative, the European olm, the mud puppy exhibits neoteny, i.e., it reaches sexual maturity without losing its larval characteristics. Adults have lungs, characteristic of most adult salamanders, as well as gills, characteristic of larvae. Their short, sturdy limbs develop at an early stage. The mud puppy may reach a length of 12 in. (30 cm); it is reddish brown and black-spotted above and grayish below, with conspicuous bushy red gills at the sides of its head. It walks on river bottoms and feeds primarily on crayfish and aquatic plants. Mud puppies are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Urodela, family Proteidae.