Triparatanais, Bamber, Roger N & Chatterjee, Tapas, 2010

Bamber, Roger N & Chatterjee, Tapas, 2010, The new and the old: littoral tanaidomorph Tanaidacea (Crustacea: Peracarida) from the Andaman Islands, Indian Ocean, Zootaxa 2558, pp. 17-32 : 22-23

Genus Triparatanais gen. nov.

Diagnosis: paratanaid with antennule of three longer articles plus minute distal article; eyes present; setae on antennules, antennae and chelipeds not exceedingly long, not setulose; distal article of antennule with eccentric distal tip, most setae and aesthetasc mounted subdistally; second article of the antenna without ventral expansion or distal seta-bearing apophyses, stout dorsodistal spine present on third article; plumose lateral setae present on pleonites 1 to 4; wide maxilliped endite bearing distal rounded tubercles; dactylus and unguis of posterior pereopods fused into a claw; uropod exopod 1-segmented, endopod 2-segmented.

Etymology: from the Greek treis (Latin tre) – three, referring to the taxon having only three longer articles in the antennule.

Type species: Triparatanais meios sp. nov.

Remarks. The presence of plumose lateral setae on the anterior four pleonites is a diagnostic character of the Paratanaidae (see Bamber, 2008)1. The attachment of the coxal sclerite of the cheliped to the cephalon was not clearly observed. With the conformation of the maxilliped endite, and of the antennular and antennal setae, the present genus falls into the subfamily Paratanaidinae , and is close in most aspects of its morphology to the increasingly speciose genus Paratanais Dana, 1852 .

With its unique (for the family) morphology of only three longer articles in the antennule, it is considered valid (and valuable) to distinguish the present taxon at the generic level. There is some internal indication of a constriction (but not separation) in the musculature of the proximal antennule article (at a point indicated by a faint broken line in Figure 3 B), at a point consistent with the normal articulation between first and second antennule articles in Paratanais , and this may be an indication of fusion of such articles. There is no other

1. Bird & Larsen (2009) split the genus Teleotanais , which has lateral plumose pleonite setae, from the Paratanaidae , without giving clear reasons; the split is presumably based on the maxilliped endite morphology, but, as stated in Bamber (2008) in all other respects it closely resembles species of the genus Paratanais , on which basis we choose to retain it within the Paratanaidae .

indication of fusion of a second (or third) article. While the present species is particularly small for the subfamily, and the general reduction in setation may reflect this, intrageneric loss of an antennule article has never been found to occur in unusually small species of tanaidaceans, nor is it a neotonous feature.

The pars incisiva of the right mandible is commonly distally bilobed in Paratanais species; it is unclear whether the single-lobed structure of the present species is a generic or specific character. It is not clear whether the eccentric antennule tip, with subdistal minute fourth article, is a generic feature, or one neglected in observations of some of the previously described paratanaids.

Figures

FIGURE 3. Triparatanais meios gen. et sp. nov., A, holotype female, dorsal; B, antennule; C, antenna; D, labrum; E, left mandible; F, right mandible (molar process broken); G, maxillule with distal detail (palp broken); H, labium; I, maxilliped endite; J, maxilliped. Scale line = 0.4 mm for A, 0.1 mm for D to J.