Ascaphus montanus

Tailed frog

The tailed frogs are two species of frogs. The species are part of the genus, Ascaphus is the only taxon in the family Ascaphidae. The "tail" in the name is actually an extension of the male cloaca. It is the only North American frog that reproduces by internal fertilization.


Until 2001, the genus was believed to be monotypic, the single species being the tailed frog (Ascaphus truei Stejneger, 1899). However in that year Nielson, Lohman, and Sullivan published evidence in Evolution that promoted the Rocky Mountain tailed frog (Ascaphus montanus) from a subspecies to its own species. Since then, the former species has been formally called coastal tailed frog.

General morphology

The existence of the visible "tail" appendage makes this frog family distinct from all other frogs. Thus its wider classification is difficult. It is usually classified in the Archaeobatrachia suborder of ancient frogs, though some say it should be a sister to all other frogs.

As well as the ancient tail, these frogs have a number of vertebrae higher than that normal to frogs, non-vocalisation and ribs. They are small to and are found in steeply-flowing streams in Montana, Idaho, Oregon and Washington in the northwest United States and southeastern British Columbia.

The tailed frogs share certain characteristics with the New Zealand primitive frogs, Leiopelmatidae. The prehistoric Vieraella belongs to the tailed frog family.

General habitat

The habitat of the Tailed Frog is cold, fast-moving streams with cobblestone bottoms. Tailed frogs are mostly aquatic, but adults may emerge during cool, wet conditions to forage terrestrially. Breeding season lasts from May through September, and females deposit their eggs in strings under rocks in fast-moving streams. Larvae take one to four years to metamorphose in the cool, fast-moving mountain streams.

Adults forage primarily terrestrially along stream banks but also occasionally feed underwater. A wide variety of food items taken, including both aquatic and terrestrial larval and adult insects, other arthropods (especially spiders), and snails. Tadpoles consume small quantities of filamentous green algae and desmids. Large quantities of conifer pollen are consumed seasonally by tadpoles.

During the day, adults seek cover under submerged substrates in the stream, or occasionally under similar surface objects close to the stream. Individuals have also been found in crevices in spray-drenched cliff walls near waterfalls. During winter individuals are less active, especially inland, and appear to retreat beneath large logs and boulders. Tadpoles require cool streams with smooth-surfaced stones with a minimum diameter of . Tadpoles probably spend most of their time attached to such substrates by a large oral sucker. They prefer turbulent water to ones in smooth, swiftly flowing water.


  • Gissi, Carmela; Diego San Mauro, Graziano Pesole and Rafael Zardoya (2006). "Mitochondrial phylogeny of Anura (Amphibia): A case study of congruent phylogenetic reconstruction using amino acid and nucleotide characters". Gene 366 228–237.
  • Roelants, Kim; Franky Bossuyt (2005). "Archaeobatrachian paraphyly and pangaean diversification of crown-group frogs". Systematic Biology 54 111–126.
  • San Mauro, Diego; Miguel Vences, Marina Alcobendas, Rafael Zardoya and Axel Meyer (2005). "Initial diversification of living amphibians predated the breakup of Pangaea". American Naturalist 165 590–599. – Scholar search


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