Bascestus, Błażewicz-Paszkowycz & Bamber, 2012

Błażewicz-Paszkowycz, M. & Bamber, R. N., 2012, The Shallow-water Tanaidacea (Arthropoda: Malacostraca: Peracarida) of the Bass Strait, Victoria, Australia (other than the Tanaidae), Memoirs of Museum Victoria 69, pp. 1-235 : 221-222

Genus Bascestus gen. nov.

Diagnosis. Female of leptognathioid ( sensu lato) facies, elongate. Cephalothorax longer than wide, eyelobes and eyes absent. Pleonite epimera each with long seta. Antennule fourarticled; antenna six-articled, fourth article longest, curved, without secondary articulation. Mandibular molar proximally broad, tapering, distally with numerous fine teeth; right mandible incisor not crenulate, but distally concave with adjacent stout teeth; left incisor with few distal crenulations, lacinia mobilis narrow, linguiform. Maxilliped bases fused, naked, endites not fused, distally with single rounded tubercle and small inner seta. Cheliped attached by distally rectangular sclerite, basis narrower posterior to this attachment; propodus with two ventral setae. Pereopods 1 to 3 with one seta on ischium; pereopods 2 to 6 with compound (denticulate in their distal half) spines on merus, carpus and propodus; pereopods 2 and 3 merus ventrodistally with one seta and one compound spine, pereopods 4 to 6 carpus with three spines and one seta. Ungues of anterior pereopods longer than dactyli; ungues of posterior pereopods distinct, shorter than dactyli, both articles with fine ventral denticulation. Pleopods present, functional; rami rounded, with plumose setae extending along outer margin. Uropod biramous, basis without distal apophyses, rami slender, endopod and exopod of two segments.

Male much less elongate than female, antennule of five articles; other appendages similar to those of female, mouthparts functional.

Etymology. From “Bass” as in Bass Strait, and the Greek (but with Latin pronunciation) cestus – a reinforced boxing glove, alluding to the nodulose chela of at least the type-species of this genus (male).

Type species: Bascestus melmackenziae sp. nov.

Remarks. The species described below shows morphological affinities with such genera as Leptognathiella Hansen, 1913 , Leptognathioides Bird & Holdich, 1984 , Stenotanais Bird & Holdich, 1984 , and Kanikipa Bird, 2011 , without conforming to any single one of these. Thus the mandibular structure, particularly the right incisor and the tapering molar, resemble those of the first three of these three genera, the last two of which also show some ventrodistal carpal expansion to accommodate the reflexion of the chela; the linguiform lacinia mobilis of the left mandible is also consistent with most species of these four genera, while the molar dentition resembles that of Leptognathiella and Stenotanais . The presence on the merus of the anterior pereopods of a ventrodistal seta and a ventrodistal spine is consistent with Leptognathioides and Kanikipa (but also the nototanaid genus Tanaissus and the agathotanaid genus Paragathotanais ), while denticulation of the posterior dactyli accords with Stenotanais and Akanthophoreus inter alia (the latter also having a similar mandibular molar morphology).

Thus, there is no particular characteristic of Bascestus gen. nov. that distinguishes it from a number of others once allocated to the Leptognathiidae sensu Sieg, 1976b , but their combination in the present taxon is unique and excludes it from any of those genera. In having sexual dimorphism possibly limited to the antennular structure and habitus proportions, the present genus is further distinct from many other “leptognathiid” genera (in a number of which males remain unknown).

Since the insightful work of Bird and Holdich (1984), which highlighted the distinctions of a number of these genera previously subsumed into Leptognathia Sars, 1882 , and sensibly discussed the relative merits of different characters for distinguishing different taxon levels, these taxa have been moved variously into such families as the Anarthruridae Lang, 1971 , thence to the Colletteidae ( Leptognathiella and Leptognathioides ), the Akanthophoreidae ( Akanthophoreus ) or currently incertae sedis sensu Larsen and Wilson (2002) ( Stenotanais , Kanikipa ). Owing to its apparent affinities as described above, we choose at present to place Bascestus in the Colletteidae sensu Larsen and Wilson (2002) .