The Barton Springs Salamander (Eurycea sosorum) was not formally described until 1993, despite being known from the springs for at least 50 years. It is a member of the family Plethodontidae, which is the largest family of salamanders. It is in the sub-family Spelerpinae (Chippindale, Bonett, Baldwin, and Wiens, 2004, Evolution, 58: 2809-2822; Macey, 2005, Cladistics, 21: 194-202), which includes four genera: Eurycea Rafinesque, 1822 (27 sp.) Gyrinophilus Cope, 1869 (4 sp.) Pseudotriton Tschudi, 1838 (3 sp.) Stereochilus Cope, 1869 (1 sp.). Eurycea sosorum is most closely related to other species that inhabit the Hill Country in central Texas, south of the Colorado River. All are members of the sub-genus Blepsimolge .
The Barton Springs Salamander, like the Jollyville Plateau Salamander, was previously recognized at a population of the then-considered widespread Texas Salamander (E. neotenes). However it differs by a set of unique molecular (DNA and allozyme markers) as well as morphological characteristics, in comparison to other Eurycea. You can view the closest relatives of the Barton Springs Salamander in this phylogenetic tree.