DESMOSOMATIDAE G. O. Sars, 1897

George, Robert Y., 2001, Desmosomatidae and Nannoniscidae (Crustacea, Isopoda, Asellota) from bathyal and abyssal depths oOE North Carolina and their evolution, Journal of Natural History 35 (12), pp. 1831-1859 : 1833-1834

FAMILY DESMOSOMATIDAE G. O. Sars, 1897

Family diagnosis (modi®ed from Hessler, 1970). Body slender and long. Cephalon not fused with ®rst pereonite. All pereonites free, pereon divided into an anterior unit of four short pereonites and a posterior unit of three long pereonites. First pleonite very short or lacking. Antennula short and located dorsally, with peduncle of two articles and ¯agellum of either three or four articles. Antenna also dorsal, long, on male thicker and ¯agellum richly armed with aethetascs. Mandibles with incisor well developed, lacinia mobilis present, middle spines strong, molar triangular with distal setae and palp three-articlulated, or reduced, or absent. Anterior four pereopods directed forwards and developed for feeding, walking or digging, fringed with ventral setae. Coxae of anterior four pereopods dorsally visible and those of the posterior pereopods usually so but not always. Posterior three pereopods directed backwards, developed for walking or feeble swimming with carpi and propodi somewhat ¯attened and provided with a fringe of long setae. Uropods ventral, endopod well developed, composed of a single article, exopod shorter or lacking.

Remarks. Historically this deep-sea family had its roots in the high latitude shallow depths oOE Norway in the mid-19th century classical crustacean investigations of Georg Ossian Sars. In 1864 Sars erected the genus Desmosoma and D. lineare as the type species known as shallow as 50 m. A second genus Eugerda was established by Meinert (1890) with the type species E. globiceps . The most signi®cant morphological diOEerences between these two genera are in the structure of the ®rst pereopod and uropod. In 1897 Sars established another genus Echinopleura , characterized by slender fourth and ®fth pereonites, uniramous uropods and palpless mandible.

Hansen (1916) questioned the validity of the genus Eugerda and divided the family under the two genera Desmosoma and Echinopleura on the basis of the morphology of the ®rst pair of pereopods. He argued that uropod morphology is useful in only distinguishing species but not genera. This idea is questionable, as it was found later by other systematists that Eugerda is a genuine genus with many distinct species. Richardson (1911) added another genus Dacylostylis with the type species D. acutispinis . However, in 1911 of the 32 known species of the family, 29 species belonged to the genus Desmosoma since the other three genera were then monotypic.

The status of the family remained in a status quo for more than a century when the Russian carcinologist Kussakin (1965) revised the family while erecting four new genera, Pseudogerda , Eugerdella , Desmosomella and Paradesmosoma , on the basis of four generic characters: (1) presence or absence of uropodal exopod; (2) presence or absence of mandibular palp; (3) structure of the ®rst pereopod; and (4) degree of expansion and setation of carpus and propodus for swimming (as in Paradesmosoma , which in the opinion of this author may not really belong to the family Desmosomatidae since it also has a modi®ed fourth pereopod). Richardson’s (1911) Dactylostylis was removed from Desmosomatidae and placed in Janiridae (WolOE, 1962) . Hessler (1970) put in perspective the proper taxonomic status for all genera (except Thaumastosoma ) and clearly divided the family under two distinct subfamilies: (1) Desmosomatina e and (2) Eugerdellatinae .