Mirandotanaidae, Błażewicz-P, 2009

Błażewicz-P, Magdalena, 2009, A new genus of a new Austral family of paratanaoid tanaidacean (Crustacea: Peracarida: Tanaidacea), with two new species., Memoirs of Museum Victoria 66, pp. 5-15 : 6

Family Mirandotanaidae fam. nov.

Diagnosis. Mature adults with strongly-inflated posterior pereonites and pleon (“abdomen”) comprising half or more of the body length. Eyelobes prominent, eyes absent. Antennule of four articles, antenna of six articles. Labrum naked or with minute setules; mandible poorly calcified, with reduced pars molaris; labium naked; maxillule palp articles fused, with two distal setae; maxilliped basis fused medially. Cheliped basis attached by distinct triangular sclerite; dactylus strongly curved. Pereopods 1 to 3 with a separate coxa, merus naked, carpus and propodus with sparse setae only (no spines); pereopods 4 to 6 coxa not distinct, merus, carpus and propodus with slender spines; dactylus and unguis not fused, unguis of pereopods 4 to 6 distally bifurcate. Pleopods absent in female, biramous with simple, mainly distal, setae, in male. Uropods short, compact, exopod of one segment, endopod of two segments.

Etymology: from the type-genus, Mirandotanais .

Remarks. The most recent comprehensive classification of the Paratanaoidea was that of Guţu and Sieg (1999), which placed Mirandotanais in the Anarthruridae Lang, 1971 . Since that time, a large number of new genera and species have been described, earlier taxa have been redescribed, and there is now a weight of evidence that their familial structure was too simplistic. Subsequent mathematical phylogenetic treatments of the Paratanaoidea by unweighted cladistic analysis have been attempted. Larsen and Wilson (2002) undertook a morphologically-based empirical parsimony analysis using eighty-one exemplar taxa, but failed to resolve a large number of genera into an overall classification. Their results suggested the inclusion of Mirandotanais in their new family Colletteidae , although their key would identify it with their other new family Tanaellidae , and some features of the genus were counter to their familial diagnosis for Colletteidae (but, curiously, not their diagnosis of Anarthruridae ).

Błażewicz-Paszkowycz and Poore (2008) undertook a similar cladistic unweighted analysis of ninety-three paratanaoid taxa; they were unable to resolve Colletteidae sensu Larsen & Wilson (2002) , indicating that this taxon is grossly polyphyletic, while Mirandotanais was isolated both from taxa associated with “ Colletteidae ” and from their clearly-resolved group of Anarthruridae ; rather, the genus was weakly-associated with Parafilitanais mexicanus and Pseudoleptognathia setosa , albeit with very low bootstrap support. These taxa are incompatible with such “colletteid” genera as Subulella , Leptognathiella , Stenotanais , Leptognathiopsis and Filitanais (which did cluster together in the analysis of Błażewicz-Paszkowycz and Poore, 2008) which are characterized by strong “spiniform setae” on pereopods1to 3, inter alia, while these are absent in Mirandotanais and in the new genus described below. The presence of weak setation on the anterior three pairs of pereopods is compatible with some species of Collettea , including the type-species C. cylindrata ( Sars, 1882) , but these setae are usually robust (cf. C. arnaudi (Shiino, 1979) ; C. pegmata Bamber, 2000 ).

All taxa in the Colletteidae sensu Larsen & Wilson (2002) other than Mirandotanais have well-developed mouthparts, with a functional mandible and fully-developed maxilliped, unlike the two genera discussed herein; conversely, reduction of the mouthparts is a characteristic feature of the Anarthruridae , together with weak setation of the anterior three pairs of pereopods. However, current understanding of the Anarthruridae includes only taxa without a uropod exopod (merely some form of apophysis on the uropod basis), unlike the two genera discussed in the present paper.

These characters (if deemed significant-enough to define families) exclude Mirandotanais and the new genus described below from either the Colletteidae or the Anarthruridae as presently diagnosed.

Until the familial classification within the Paratanaoidea is properly resolved, it is therefore necessary to assign Mirandotanais to a new family, the Mirandotanaidae .