Introduction
The common mudpuppy, Necturus maculosus, is a member of the Caudata, which together with Anura (frogs and toads) and Gymnophiona (caecilians or apodans) form the Lissamphibia. The Caudata, including the salamanders and newts, are the least specialized amphibians in body form and locomotion.
The body is elongated and stout, with well-developed axial musculature and tail. Salamanders use their limbs in combination with the side-to-side body undulations characteristic of fish, and thus probably resemble the earliest land vertebrates in locomotion. In contrast, frogs (see Chapter 6) are characterized by a shortened body and specialized saltatory locomotion, while gympnophionans are limbless burrowers.There are several clades of salamanders, of which the Plethiodontidae includes by far the most species. Salamanders range from being fully aquatic to fully terrestrial. Members of several families do not metamorphose. Necturus is commonly included with Proteus in the Proteidae, a small group of fully aquatic, neotenic (i.e., retaining juvenile features) salamanders that retain their larval, filamentous external gills, two pairs of pharyngeal slits, and caudal fins as adults. Necturus includes six species. N. maculosus is apparently closely related to N. lewisi, the Red River mudpuppy. The remaining species of Necturus are commonly referred to as waterdogs.