Diagnosis:
The Mudpuppy is a large, obligate aquatic salamander with a large flattened, square head, small eyes, and a pair of distinctive, red feathery gills on each side of its head. Mudpuppies are characterized by large size, the presence of bushy gills on each side of the neck behind the head, and four toes on each foot. The large, distinctive, bushy gills of these species are reddish or maroon; the head, body, limbs, and tail are yellowish brown, reddish, gray, or brown. The body and tail are covered with indistinct blue-black spots which vary in number. The belly is pale gray and may or may not be spotted.Adult males can be distinguished from females during the breeding season by the presence of a swollen ridge around, and crescent shaped groove just behind, the cloaca! opening. They are neotenic (retaining larval characteristics into maturity [no transformation]) and retain large external gills throughout their life. In the more clear and cool streams (e.g. Shoal Creek), their gills may be reduced, but are still quite noticeable.
They are gray or reddish-brown, to dark brown with irregularly spaced diffuse-edged blotches on the back. Rarely, the spots may merge to form stripes in adults. There is typically a diffuse dark stripe that runs from the nostril, through the eye, to the gills. The belly is whitish to light gray to light yellow, and may be spotted along the sides or spotted throughout. Specimens from the Marais des Cygnes river drainages have a greater incidence of belly spotting and a darker background than specimens from elsewhere in the state, however, all populations in Kansas may be quite variable in this respect (Taggart 2003; George and Slack 2010).
Four toes are present on each of four well-developed limbs. The cloacae of mature males have two prominent papillae directed backward. In the breeding season, the cloacae of males are swollen. Female cloacae are slit-like and often lighter in coloration. Young Mudpuppies are dark brown with longitudinal yellowish stripes.
— Neosho/Verdigris drainage; 'louisiensis' form: Adults normally 200-250 mm (8-9¾ inches) in total length. The largest Kansas specimen is a male (FHSM 7496) from Allen County with a snout-vent length of 211 mm and a total length of 307 mm (12 inches) collected by Travis W. Taggart on 22 February 2003. This specimen is the largest individual recorded throughout its range (Powell, et al, 2016).
— Marais des Cygnes drainage; 'maculosus' form: Adults normally 200-330 mm (8-13 inches) in total length. The largest specimen is sex undetermined (KU 209746) from Osage County with a snout-vent length of 262 mm and a total length of 385 mm (15¼ inches) collected by Tom Mosher on 4 April 1988. The maximum length throughout the range is 485.8 mm (191⁄8 inches) (Powell, et al, 2016).