Six extant species in two genera are recognized in this small family of paedomorphic salamanders. Geographic distribution is disjunct, with Necturus occurring in eastern North America, and the single species of Proteus restricted to southeastern Europe.

 

Metamorphosis does not occur in proteids. Adults are paedomorphic and fully aquatic. Long feathery gills are retained throughout life, as are caudal fins. Two characters that distinguish proteids from other Salamandroidea include the presence of two gill slits in adults, and a diploid number of 38 (other Proteus has a translucent or pale rose color, presumably from spending much of its time buried in mud or sand. Proteus has lost its eyes altogether, while mere retinal simplification has occurred in species of Necturus. Four Necturus species, the waterdogs, grow to 28 cm in length, and the fifth, N. maculosus, the mudpuppy, grows to more than 40 cm long. Their common names reflect the common but erroneous belief that these salamanders emit a defensive bark when disturbed. Unlike the European Proteus, American Necturus have pigmented skin. Gills in both genera are brightly colored, often red or purple.

 

Proteus lives in limestone caves; Necturus inhabit lakes or streams. Necturus maculosus courts in the autumn, but eggs are not laid until the following spring. Across the family, eggs are attached to submerged stones or logs. Parental care is exhibited by either males or females, in the form of egg attendance. Larvae take several years to reach maturity. Adults feed on bacteria, protozoans, and slime, as well as invertebrates and fish. Fleshy modifications of the lips that prevent water and prey from escaping during suction feeding, called labial lobes, are present in Necturus.

 

Proteids are members of the suborder Salamandroidea, the "advanced salamanders" that include all internally-fertilizing salamanders. The grouping of the genera Necturus and Proteus into the same family has been controversial, and this taxonomy (the family Proteidae) may not hold. Some analyses place the proteids basal to the other Salamandroidea; most do not. Some current analyses suggest that the Ambystomatidae, Dicamptodontidae, Salamandridae and the proteid genus Necturus all form a monophyletic group, but it is not clear where Proteus falls in this evolutionary reconstruction.

 

Two extinct genera are recognized. Fossil Mioproteus are known from the Miocene in the Caucasus Mountains, fossil Orthophyia are known from the Miocene in Germany. Fossil Necturus are known from the Paleocene (Canada) and Pleistocene (Florida), and fossil Proteus are known from the Pleistocene (Germany).

 

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