the southeastern Pacific was synonymized with this species by Kato, Springer and Wagner in 1967, but was later tentatively recognized as a separate species again by Leonard Compagno. The taxonomic status of angel sharks in the southeastern Pacific – whether they are S. californica, S. armata, or if there is more than one Squatina species in the region – remains unresolved. The angel sharks inhabiting the Gulf of California may also represent a different species, as they mature at a much smaller size than those from the rest of their range. A phylogenetic study based on mitochondrial DNA, published by Björn Stelbrink and colleagues in 2010, reported that the sister species of the Pacific angelshark is the sand devil (S. dumeril) of the western North Atlantic. The two species are estimated to have diverged approximately 6.1 Ma, close to when the Isthmus of Panama first began to form. The authors also found that Pacific angelsharks from the Gulf of California differed genetically from those elsewhere, though they were equivocal as to whether this represented a species-level distinction. Distribution and habitat Pacific angelsharks are found in cold to warm-temperate waters from the southeastern corner of Alaska to the Gulf of California, including the entire Baja peninsula, and are most common off central and southern California. It may also occur from Ecuador to the southern tip of Chile (see taxonomic uncertainty above). This bottom-dwelling shark prefers habitats with soft, flat bottoms close to shore, such as estuaries and bays, and are often found near rocky reefs, submarine canyons, and kelp forests. On occasion, they have been seen swimming above the sea floor. Off California, the Pacific angelshark is most common at a depth of , but has been reported from as deep as . A number of genetically discrete subpopulations have been identified across the northern range of the Pacific angelshark. Several subpopulations exist along the coast from Point Conception northward to Alaska. In the Southern California Bight, there are at least three separate subpopulations off the mainland and northern and southern Channel Islands. The subpopulation along the Pacific coast of Baja California are distinct from those in the Gulf of California. These subpopulations have diverged from one another over time because Pacific angelsharks do not undertake long migratory movements outside of their preferred home areas, and deep waters serve as effective geographical barriers to population mixing. Heterozygosity, a measure of genetic