Redescription of Hexanchus nakamurai Teng 1962, (Chondrichthyes: Hexanchiformes: Hexanchidae), with designation of a neotype

Hexanchus nakamurai Teng, 1962 is one of two valid nominal species in the genus Hexanchus; the other being H. griseus. The taxonomic history of H. nakamurai is somewhat convoluted due to questions about the validity of whether it constituted a publication or an unpublished dissertation. The issue appeared to have been resolved once it was determined that the Teng's original description met the criteria under the International Commission on Zoological Nomenclature code (Article 8a) of a publication. However, recent molecular studies have indicated that the western North Atlantic H. nakamurai (=?H. vitulus) may be distinct from western Indian Ocean H. nakamurai. Compounding the issue is the loss of the holotype of H. nakamurai from Taiwan. A neotype is herein designated and the species redescribed based on the neotype and eight additional Taiwanese specimens.