Ozark Hellbenders (Cryptobranchus alleganiensis bishopi) are just one of the many subspecies of salamanders. As they come from the family Cryptobranchidae, there are only two genera within this family. One genera within this family is the hellbenders (Cryptobranchus alleganiensis) and the other being the giant salamanders (Andrias japonicus). Although these two groups come from different parts of the world, both supspecies from China and Japan and North America, have ancestral history that dates back 160 million years ago (Rachel S. Crowhurst et al., 2010). 

"Thus, both their study and the present study based on nuclear DNA suggest that the Ozark hellbender subspecies is paraphyletic (Rachel S. Crowhurst et al., 2010)."

"From fossil evidence in Asia, the evolutionary origins of the Cryptobranchidae extend to at least the Mid-Jurassic (160 million years ago [MYA]; Gao and Shubin 2003), with their fossils later being known from Europe, Asia, and North America (Robert K. Brown et al. 2012)."

According to a research article done on the palaentology and phylogeny of this family, this family of ancient salamanders have experienced remarkable stasis throughout evolution, and they have maintained significant similarity to their ancestors (Robert K. Brown et al. 2012).