Few, if any, amphibians and reptiles are endemic to Utah. This is also true for much of the Great Basin, upper Colorado Plateau, southern Idaho, and Wyoming. Many species that would seemingly survive in this inland, mountainous area are not here. Only one widespread salamander and a few frogs and toads have occupied suitable habitats in the area. Lizards and snakes, like the amphibians, provide few distributions that extend throughout the area. A migration which presumably followed the Pleistocene Ice Age brought most of the species into the area as climatic conditions warmed.
Distribution maps of our modern species and subspecies indicate rather clearly that these vertebrates have invaded the Intermountain Region in relatively recent geological time. Only the periphery of Utah and adjoining states to the east and west have been penetrated by many of the species in the regional fauna.
Tanner, Wilmer W.
"Zoogeography of reptiles and amphibians in the Intermountain Region,"
Great Basin Naturalist Memoirs: Vol. 2
, Article 4.
Available at: http://scholarsarchive.byu.edu/gbnm/vol2/iss1/4