A vicariance hypothesis of New World biogeography involving transport of living biota on fragments of an ancestral landmass to present positions ranging from southern Alaska to northern South America is developed. Geological, as well as biogeographical, ecological, and systematic data from plethodontid salamanders provide correlative support for the model. Other groups appear to have similar biogeographic histories and, along with further geological data, could provide means of corroboration of this hypothesis. Active biotic dispersal between the American continents before Pliocene closure of the Panamanian isthmus may have been less prevalent than previously believed, and tectonic transport may have dispersed many organisms. If corroborated, geologists may be provided a new method of analyzing relationships among “suspect terranes” using phylogenetic analyses of living biota, and biologists may be required to reassess previous concepts of New World historical biogeography.