Necturus is a genus of aquatic salamanders in the family Proteidae. Species of the genus are native to the eastern United States and Canada.[2][3][4] They are commonly known as waterdogs and mudpuppies.[2][3] The common mudpuppy (N. maculosus) is probably the best-known species – as an amphibian with gill slits, it is often dissected in comparative anatomy classes. The common mudpuppy has the largest distribution of any fully aquatic salamander in North America.[5]
The genus Necturus is under scrutiny by herpetologists.[2] The relationship between the species is still being studied. In 1991 Collins reelevated N. maculosus louisianensis to full species status as N. louisianensis. Originally described by Viosca as a species, it usually had been considered a subspecies of the common mudpuppy (N. maculosus). However, the interpretation of Collins was not largely followed.[2][6][7] Then, a 2018 study confirmed it as a distinct species, with Amphibian Species of the World following these results, although other authorities do not.[8][9][10]
Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Necturus.
Two known fossil species, N. krausei and an unnamed species, are respectively known from the Paleocene of Saskatchewan and from Florida during the Pleistocene.[12][13]
Necturus are paedomorphic: adults retain larval-like morphology with external gills, two pairs of gill slits, and no eyelids. They are moderately robust and have two pairs of short but well-developed limbs and a large, laterally compressed tail. Lungs are present but small. Typical adult size is 20–25 cm (8–10 in) in total length, but Necturus maculosus is larger and may reach 40 cm (16 in).[4]
N. maculosus is brown to gray on its back with bluish black spots. There may be spots on its belly, but these spots range from heavily spotted to no spotting. There are dark red bushy gills. Four toes are present per hindlimb.[14]