Resurrection and redescription of Squalus suckleyi (Girard, 1854) from the North Pacific, with comments on the Squalus acanthias subgroup (Squaliformes: Squalidae)

A taxonomic re-evaluation of the status of the North Pacific Squalus suckleyi (Girard, 1854) combining the use of meristic, morphological and molecular data reveal this species to be clearly distinct from the widespread Squalus acanthias (Linneaus, 1758). Differences in the external morphology between S. acanthias and S. suckleyi are subtle and are likely to be masked by intraspecific variation within individuals. However, we found S. suckleyi to differ from S. acanthias based on the following morphological and meristic characteristics: a short, broadly-rounded to acute snout; first dorsal-fin midpoint more posterior to pectoral-fin insertion; pelvic-fin origin closer to second dorsal fin than first dorsal fin; total vertebral counts average 99 (97-106). Molecular analysis of approximately 650 bp of the CO1 mitochondrial gene (DNA barcode region) showed separation of S. suckleyi and S. acanthias into two distinct genetic clades with 98% bootstrap support. Within species genetic diversities were 0.109 +/- 0.036% and 0.176 +/- 0.041% for S. suckleyi and S. acanthias respectively; between species diversity was 5-6 fold greater at 0.765 +/- 0.307%. Squalus suckleyi is thus resurrected and a neotype for this endemic North Pacific Squalus species is designated.