Hedgpethia Turpaeva, 1973

Takahashi, Yoshie, Dick, Matthew H. & Mawatari, Shunsuke F., 2007, Sea spiders (Arthropoda: Pycnogonida) from waters adjacent to the Nansei Islands of Japan, Journal of Natural History 41 (1 - 4), pp. 61-79 : 69-70

Genus Hedgpethia Turpaeva, 1973

Diagnosis. Trunk with lateral processes well separated like Colossendeis ; segments with expanded ridges posteriorly; proboscis massive, usually spindle-shaped, distally tapering and rounded, or truncate; without dorsal tooth; chelifores lacking; palps 10-segmented, long and slender with very tiny second segment; ovigers 10-segmented, strigilis in both sexes usually with rows of slender spatulate spines, with terminal claw; legs slender, with tiny setae, without well-developed tubercles; tarsus and propodus cylindrical, mostly straight; auxiliary claws lacking. Cement glands unknown.

Remarks. The genus Hedgpethia includes 12 known species. All of these are fairly small in body size compared to most species of Colossendeis , the type genus of Colossendeidae . Most Hedgpethia species have been collected infrequently, at only a few sites, and many are known only from their type locality. Species of Hedgpethia have been collected from a wide range of depths, from 20 to 4294 m.

Hedgpethia is related to Rhopalorhynchus Wood-Mason, 1873 . Stock (1958) divided Rhopalorhynchus sensu lato into two species groups: the articulatum group and the kröyeri group, corresponding to the present genera Hedgpethia and Rhopalorhynchus sensu stricto, respectively, and suggested that the two groups evolved from a common ancestor. Turpaeva (1973) established Hedgpethia for species originally in Rhopalorhynchus that lack a tooth on the proboscis.

In general, Hedgpethia species inhabit warm- to cool-temperate waters, whereas Rhopalorhynchus species occur in shallow tropical waters. In contrast to Rhopalorhynchus , species of Hedgpethia are distributed in the northern Pacific Ocean from California to Japan, and also occur from eastern Australia to southern New Zealand. Three geographically isolated species are also known: H. atlanticum ( Stock, 1970) from the northeastern Atlantic Ocean, including the Mediterranean; H. magnirostris Arnaud and Child, 1988 from the Zululand area, South Africa; and H. dampieri Child, 1975 , from near Lancelin Island, southwestern Australia.

In the Pacific Ocean, Hedgpethia is broadly distributed in both the northern and southern hemispheres, whereas in comparison Rhopalorhynchus is restricted to the Indo-West- Pacific. Although the two genera occur sympatrically in South Africa and western Australia, and from northern Australia to New Caledonia, they generally appear to have different but partly overlapping depth ranges, with Rhopalorhynchus occurring from 0 to 320 m and Hedgpethia from 20 to 4294 m. The two genera are now considered as having largely nonoverlapping distributions in three-dimensional space.