 Furthermore, the average size of "C. a. alleganiensis" has been reported to be 45–60 cm (with some reported as reaching up to 74 cm or 30 in), while "N. m. maculosus" has a reported average size of 28–40 cm in length, which means that hellbender adults will still generally be notably larger than even the biggest mudpuppies.The genus "Cryptobranchus" has historically only been considered to contain one species, "C. alleganiensis", with two subspecies, "C. a. alleganiensis" and "C. a. bishopi".A recent decline in population size of the Ozark subspecies "C. a. bishopi" has led to further research into populations of this subspecies, including genetic analysis to determine the best method for conservation.