By Heather Heying
Four extant species in a single genus are recognized in this small family of salamanders. The family is known only from the Pacific Northwest, ranging from northern California to southern Canada, and the Rocky Mountains of Idaho and Montana.
Dicamptodontids resemble ambystomatids, but are larger (up to 30 cm snout-vent length). Lungs are well developed, teeth are blade-like, carpal and tarsals ossified in adults, and the diploid number is 28. Facultative paedomorphosis occurs in most species, though individuals in these species usually metamorphose fully into terrestrial adults with robust bodies and limbs, broad heads, and laterally-flattened tails. One species, Dicamptodon copei, does not metamorphose, retaining gills and an aquatic habit through adulthood.
Pacific giant salamanders live in coniferous forests. Eggs are deposited singly in cold streams, and the larval period is long (two to five years). Parental care occurs in the form of maternal egg attendance. Larvae inhabit springs and streams, living under rocks, and feeding on the larvae of other salamander species. Adults live under logs, bark or stones in the forest, and come out at night after strong rains. Unlike most salamanders, at least one species (Dicamptodon ensatus) has the capacity for vocalization, and emits low-pitched barks when disturbed.
Dicamptodontids are members of the suborder Salamandroidea, the "advanced salamanders" that include all internally-fertilizing salamanders. The family was recently formed when the type genus, Dicamptodon, was removed from the Ambystomatidae. Dicamptodontidae and Ambystomatidae are sister to each other. The genus Rhyacotriton was removed from Ambystomatidae around the same time, and the resultant family, Rhyacotritonidae, is probably basal among the Salamandroidea. Originally, the subfamily Rhyacotritoninae was placed within the Dicamptodontidae, but recent molecular work provides strong evidence that this maintains a paraphyletic group. Current analyses suggest that the Ambystomatidae-Dicamptodontidae clade (not including Rhyacotriton) is sister to Salamandridae.
Fossils from two extinct genera and the single extant genus are known from as far back as the Paleocene in North America. The fossil record shows greater geographic distribution than do extant forms, and European fossils are known from the Paleocene and Miocene (three extinct genera).
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Contributors
Heather Heying (author).
