Leptochiton belknapi Dall, 1878

Sirenko, Boris I., 2020, New shelf and bathyal Philippine leptochitons (Mollusca: Polyplacophora Lepidopleurida), Zootaxa 4878 (3), pp. 467-500 : 496

Leptochiton belknapi Dall, 1878

Reports of Leptochiton belknapi from the Philippines (off Luzon Island and South of Mindanao Island ( Haddon 1886; Kaas 1990) are erroneous. Sirenko & Sellanes (2016) showed that L. belknapi sensu stricto occurs in the Pacific Ocean from Hokkaido (40°12’N), via the Sea of Okhotsk into the Bering Sea, and in North and South America’s Pacific waters southwards to 42°40’S, at depths of 100 to 3724 m. The closest deep-sea relatives of the Philippine specimens that were assigned to L. belknapi are L. simplex ( Nierstrasz, 1905) from the Makassar Strait and L. giganteus ( Nierstrasz, 1905) from the Banda Sea. These two species were synonymized as either L. alveolus (M. Sars MS, Lovén, 1846) (e.g., Ferreira 1979; Kaas & Van Belle 1985) and or as L. belknapi (e.g., Kaas & Van Belle 1987). Sirenko (2015) already discussed that the L. belknapi group comprises several taxa that should be considered valid including L. giganteus that differs from L. belknapi by having the width of the jugal sinus almost equal to the width of the apophyses (whereas the width of the jugal sinus is much wider than the apophyses in L. belknapi ) and by having dorsal scales without ribs. Leptochiton simplex was treated as a synonym of Leptochiton japonicus ( Thiele, 1909) by Sirenko (2015) but is here re-instated as valid species, which differs from L. belknapi by having dorsal scales with 6 ribs (vs. 2–3 ribs in L. belknapi ). I suggest to preliminarily call specimens that have been identified as L. belknapi in the above-mentioned works L.? belknapi until these specimens can be studied in more detail.