Comments: Based on international differences in control of exploitation and regulatory mechanisms, the U.S. population meets the discreteness requirements for a "species" under the U.S. Endangered Species Act (NMFS 2001). The U.S. population also qualifies for consideration under the U.S. ESA because it is the northernmost population in the western Hemisphere and is not known to be in contact with other populations.
Faria et al. (2013) used mtDNA and contemporary genetic analysis to argue that the previously classified P. pristis, P. microdon, and P. perotteti should be regarded as a single species (P. pristis).