Obesutanais, Larsen & Błażewicz-Paszkowycz & Cunha, 2006

Larsen, Kim, Błażewicz-Paszkowycz, Magdalena & Cunha, Marina R., 2006, Tanaidacean (Crustacea: Peracarida) fauna from chemically reduced habitats-the lucky strike hydrothermal vent system, mid-atlantic ridge, Zootaxa 1187, pp. 1-36 : 15-16

Genus Obesutanais n. gen.

Diagnosis

Body habitus short and stout (almost pseudotanaid­like) with a wide head. Body tapering off posteriorly. Pleon curved ventrally. Antennule with long setae on article 1. Mandibular molar with few distal spines. Maxilliped endite with one distal tubercule. Pereopods all with many setules and cuticular scales. Pereopods 2 and 3 merus with one seta as long as or longer than carpus; carpus with a long seta (almost as long as propodus). Pereopods 4–6 without ornamented process (clinging process); unguis bifurcate. Pleopod setation restricted to the distal end (except for the endopod proximal seta); large gap between endopod proximal seta and other setae; long (more than half the length of endopod). Uropod endopod with two incompletely fused articles (pseudo­uniarticulate); endo­ and exopod with thick specialized terminal setae; exopod unarticulated, almost as long as endopod.

Type species Obesutanais sigridae n. sp., here designated.

Etymology Name alluding to the fat body (Latin: obesus = fat).

Remarks

The typhlotanaid component of the family Nototanaidae is overburdened and heterogenous. The genus Typhlotanais alone contains 56 species and is currently under revision (Błaźewicz­Paszkowycz personal communication). Several genus­level typhlotanaid groups can be recognized, but the new genus differs from these in a number of characters. The pleopod setation being restricted to the distal end and the relatively large gap between the proximal seta and the other setae, are unique to the new genus. The maxilliped endites have only one distal process while most typhlotanaids have two, although they may be of different size. The long meral and carpal setae of the pereopods 2 and 3 are also a unique character.

Members of the genera Typhlotanais G.O. Sars, 1882 and Peraeospinosus Sieg, 1986 have pereopods 4–6 shortened, thick and, in their natural position, curved upwards as an adaptation to clinging inside tubes. The outer margin of merus and carpus of such legs contribute to this clinging apparatus (which in most Typhlotanais sensu lato consists of processes of various size), being covered with hooks and numerous short setae or well calcified spines. Obesutanais has no such processes but the clinging apparatus is formed by a pair of spines on both merus and carpus and numerous short setae and well calcified spines that are arranged in ‘combs’.

One other species, listed as ‘ Typhlotanais sp.,’ was found in a hydrothermal vent habitat ( Larsen 2005) also belongs in this new genus and three additional from the North Atlantic are under description (Bird & Błaźewicz­Paszkowycz personal communication).