Tailed Toad

Tailed toads are two species of toads in the family Ascaphidae, both belonging to the genus Ascaphus. Ascaphus is the only taxon in the family Ascaphidae (pronounced /æˈskæfɨdiː/). The "tail" in the name is actually an extension of the male cloaca. The tail is one of two distinctive anatomical features adapting the species to life in fast-flowing streams. It is the only North American frog that reproduces by internal fertilization (most North American frogs and toads fertilize the eggs externally in amplexus).

Classification
Although sometimes referred to as "tailed frogs", these creatures are taxonomically classified as toads (order Archaeobatrachia). They are placed in the superfamily Bombinatoroidea; i.e. they are more closely related to fire-bellied toads than to true toads. Within the superfamily Bombinatoroidea, the tailed toads are placed in their own family, Ascaphidae. Both species are part of the type and only genus in the family, Ascaphus. Until 2001, the genus was believed to be monotypic, the single species being the tailed frog (Ascaphus montanus). However in that year Nielson, Lohman, and Sullivan published evidence in Evolution that promoted the coastal tailed frog (Ascaphus truei) from a subspecies to its own species. Since then, the former species has been formally called the mountain tailed frog.

Morphology
Tailed toads are usually classified in the Archaeobatrachia suborder of toads, though some say they should be placed in Neobatrachia as, like the dendrobatids, they reproduces via internal fertilization. The "tail" is found only in males, and is actually part of the cloaca, used to insert sperm into the female during mating. This anatomical feature improves breeding success by minimizing loss of sperm in the turbulent, fast-flowing streams inhabited by this species. Thus, the tailed frogs exhibit internal fertilisation like Neobatrachians, rather than the external fertilisation found in other frogs and toads. These frogs are primitive in having a greater number of vertebrae than other frogs, in lacking the ability to vocalise, and in possessing free ribs. Both species are smal: A. montanus averages 2.5 centimetres (0.98 in) in length from snout to vent; A. truei averages 5 centimetres (2.0 in) long from snout to vent. The two species also differ in coloration. A montanus ranges from walnut brown to wood brown; A. truei ranges from yellowish green to mint green. Both species are found in steeply-flowing streams in Montana, Idaho, Washington, Oregon, and northern California in the northwest United States and southeastern British Columbia.