The genus Hedgpethia Turpaeva, 1973 (Pycnogonida: Colossendeidae): a review and a new species

Hedgpethia Turpaeva, 1973 (Arthropoda: Pycnogonida: Colossendeidae) includes 18 species, but the sparsity of samples makes this genus poorly known or studied. Available identification keys are outdated, and checklists and diagnoses need revision. Here, I provide the description of Hedgpethia nosferatu sp. nov. based on a female specimen sampled at 310–403 m depth to the south of New Caledonia during the KANACONO expedition, and a revised identification key and diagnosis of the genus Hedgpethia. Hedgpethia is divided into Northern Pacific and Southern Indopacific species, plus one species in the Atlantic. Except for the Northern Pacific, this distribution is similar to that of its sister-clade Rhopalorhynchus Wood-Mason, 1873. The bathymetric distribution of Hedgpethia also partly overlaps with that of Rhopalorhynchus, but extends much deeper, often between 40 and 1500 m, and sometimes as deep as 4200 m. Characters shared among the species of Hedgpethia are potentially plesiomorphic, raising the question of the potential paraphyly of the genus. Some poorly explored characters such as the shape of the ovigeral claw, and the multiplication of molecular datasets, could bring some further insight.