A redescription of Leptochiton belknapi Dall, 1878 (Mollusca: Polyplacophora: Leptochitonidae), the type species of the new genus Belknapchiton

Leptochiton belknapi is revisited, based on a morphological study of more than 340 specimens from different localities in the Pacific Ocean; intraspecific and age variability has been determined and a confirmed distribution of this species has been compiled. The restudy of the species allowed to test the usefulness of a combined character set, which mainly focuses on body size, perinotum coverage, tegmental structures and radula characteristics. By doing so, it turned out that the intraspecific variability is less pronounced than previously assumed. The obtained results and comparison with morphologically similar species, leads to the erection of the new genus Belknapchiton, with Leptochiton belknapi being its type species. The new genus differs from the genus Leptochiton by its elongate oval, large body, rather narrow, sharply pointed perinotum scales with scattered needles, a short radula with a wide central tooth, short first lateral teeth and a strong unidentate (sometimes with denticle-like appendage) head of the second lateral teeth. The vast majority of the 22 species of the new genus inhabit the deep waters of the Pacific Ocean and only B. alveolus (M. Sars MS, Loven, 1846) is known from the Atlantic Ocean.