Two new Rhynchothorax sea spiders from Japan

Spixiana 47 (1): 15-28, DOI: 10.5281/zenodo.16851490 We describe two new sea-spider species, Rhynchothorax nopperabo sp. nov. and Rhynchothorax monoceros sp. nov., from Japan. Rhynchothorax nopperabo, collected from intertidal gravel at Shiriuchi, Hokkaido, resembles R. vallatus Child but differs from the latter in the number and shape of spines on the oviger, number of posterior tubercles on the first lateral process, and length of the auxiliary claws.

An 18S rRNA sequence was determined for R. nopperabo for future DNA barcoding. Rhynchothorax monoceros sp. nov., collected from dead corals on Amami-Oshima Island, Kagoshima, resembles R. mediterraneus Costa but differs from the latter in the lack of dorsal tubercles on the third lateral process, lack of mid-ventral spines on the oviger seventh segment, and presence of dorsal tubercle on first coxa of fourth leg. A key to species in Rhynchothorax is provided.