Four species in a single genus are recognized in this small
family of brook-dwelling salamanders. Geographic distribution is
limited to the northwestern coastal United States, from Northern
California through Washington, especially in the Cascade
mountains. Torrent salamanders are characterized by unique
squared-off glands behind the vent in adult males. Other
morphological traits that distinguish this family include the
absence of an operculum and opercularis muscle (otherwise absent
only in a few species of hynobiids), and greatly reduced lungs
(also observed in all plethodontids and a few species of
hynobiids). Torrent salamanders have several adaptations for
their life in fast-moving streams, including reduced gill rami,
short fimbriae, and restriction of tail fins posterior to the
vent. Maximum adult snout-vent length is 6 cm, but body size
varies widely among populations. Torrent salamanders exhibit
complete metamorphosis, although some paedomorphic characters
have been identified in adults, including t