Adult coloration is greenish, yellowish brown or slate gray with black spots or blotches (Petranka 1998). Two subspecies are recognized based on differences in geographic distribution (see below) and coloration. Cryptobranchus a. alleganiensis, the eastern hellbender, has small dark spots dorsally and a uniformly colored chin. Cryptobranchus a. bishopi, the Ozark hellbender, has larger black blotches dorsally and a darkly mottled chin region. The spiracle opening is also smaller in C. a. bishopi (Dundee and Dundee 1965; Dundee 1971; Nickerson and Mays 1973; Petranka 1998). Small larvae are uniformly dark dorsally with a white venter. Older larvae have dark spots dorsally and pigmented venters (Petranka 1998).
Some authors have suggested that the two currently recognized supspecies should be treated as separate species. The ranges apparently do not contact, and the morphological differences suggest reproductive isolation and absence of gene flow between the forms (Collins 1991).
- Conant, R. and Collins, J. T. (1991). A Field Guide to Reptiles and Amphibians: Eastern/Central North America. Houghton Mifflin, Boston.
- Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
- Kawamichi, T. and Ueda, H. (1998). ''Spawning at nests of extra-large males in the Giant Salamander Andrias japonicus.'' Journal of Herpetology, 32, 133-136.
- Collins, J. T. (1991). "A new taxonomic arrangement for some North American amphibians and reptiles." Herpetological Review, 22, 42-43.
- Dundee, H. A. (1971). ''Cryptobranchus, and C. alleganiensis.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 101.1-101.4.
- Dundee, H. A., and Dundee, D. S. (1965). ''Observations on the systematics and ecology of Cryptobranchus from the Ozark Plateaus of Missouri and Arkansas.'' Copeia, 1965(3), 369-370.
- Nickerson, M. A., and Mays, C. E. (1973). The Hellbenders: North American ''Giant Salamanders''. Milwaukee Public Museum, Milwaukee, WI.
- Peterson, C. L. (1988). "Breeding activities of the hellbender in Missouri." Herpetological Review, 19, 28-29.