Ascaphidae (see family information on Tree of Life site)

2 species in 1 genus

Tailed Frogs

This group is composed of two species that inhabit cold, fast flowing streams from British Columbia, south to Mendocino County (California) and east to the Rocky Mountains of Idaho and Montana. The most striking feature of this group is the external copulatory organ (an everted extension of the cloaca), used during internal fertilization, which takes place under water in fast flowing streams. The copulatory organ is controlled by the same muscle which controls the wagging of a dog's tail, the caudalipuboischiotibialis (the muscle is only found in this family among frogs). Tadpoles have large sucker-like mouths (gastromyzophory) to aid in clasping to rocks while they feed. Tadpoles may take up to 7 years to metamorphose, although 4 is average. They are small, brown or gray, have reduced lungs, and vertical pupils. Males do not vocalize. Morphological features for this group are: 1) 9 presacral vertebrae; 2) sternum cartilaginous, omosternum present; 3) urostyle with one condyle; 4) free ribs present on 3rd, 4th, and 5th vertebrae; 5) pectoral girdle arciferal; 6) clavicle overlies scapula; 7) maxilla and premaxillae contain teeth; 10) sartorious not a separate muscle; 11) aquatic larvae (Type III); 12) pupil vertically elliptical; 13) internal fertilization.

Ascaphus truei
Photo by Brad Moon
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Genus Ascaphus (2 species)
Ascaphus montanus AmphibiaWeb account photos no sound/video
Ascaphus truei AmphibiaWeb account photos no sound/video

Citation: AmphibiaWeb: Information on amphibian biology and conservation. [web application]. 2016. Berkeley, California: AmphibiaWeb. Available: (Accessed: 2016).

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