Periparatanais Bird 2019, n. gen.

Periparatanais n. gen.

Diagnosis. Female. Paratanaidin, with eyes present. Pereonites all shorter than broad. Pleonites 1–4 epimera with simple seta and thick circumplumose seta. Antennule three-articled, article-1 composite, slightly tumid; article-3 with eccentric distal tip (apical spur). Antenna article-2 with ventral ridge, ventral seta mid-length. Mandible molar with apical rosette of spines. Maxillule endite with at least eight terminal spines, at least three hooked. Maxilliped endites with incisor-shaped distal tubercles. Cheliped palm with slender distolateral spine adjacent to fixed finger; latter with tricuspid distal incisive margin; dactylus with one flat ventral spine. Pereopod-1 basis with superior seta. Pereopods 2–3 carpus inferodistal crotchets short and unequal. Pereopods 4–6 coxa with posterior apophysis bearing two apical spines; merus with crenulate/spinulate inferior ridge; carpus with paired inferior spinulate ridges, one superodistal seta and three distal crotchets. Uropod peduncle shorter than endopod; endopod twosegmented; exopod one-segmented, shorter than segment-1 of endopod.

Male. Unknown.

Etymology. Combination of Greek prefix περι (peri) ‘around’, ‘near’, and the genus name Paratanais.

Gender. Male.

Type species. Periparatanais mergaxilla n. sp., by monotypy.

Remarks. This genus is outstanding among the known paratanaidins in having a truly three-articled antennule (cf. Triparatanais with incomplete fusion, see below) and the remarkable spinose apophysis on the coxa of pereopods 4–6. In addition, the carpal setation of pereopods 4–6 of Periparatanais n. gen. appears to diverge from many paratanaidins and Metatanais in having only three serrulate crotchets (spines) rather than four: although this observation is confounded by the apparent sparsity of spines for this article and others shown in the literature for some species and genera (e.g. Xeplenois anemos Bamber, 2005: 719, fig. 54E–G; and Paratanais oculatus Vanhöffen, 1914 by Shiino (1978): 72, fig. 40E)—it is not known whether this is real or due to artefactual or inadequate recording of these structures. Despite this, Periparatanais probably has its closest phylogenetic affinity with Pseudobathytanais sensu stricto, i.e. represented by the species P. shtockmani Kudinova-Pasternak, 1990. These two genera exclusively share the characters of incisor-like maxilliped endite tubercles (not semi-circular, as long as or shorter than broad in other paratanaidin genera), a ventral or ventrolateral ridge on article-2 of the antenna, and a three-spined carpus of pereopods 4–6 (assuming it is valid in Pseudobathytanais). Other characters that may be shared (not exclusively) by the two genera are the short merus of pereopods 2–3 and uropod configuration. Note that the maxilliped palp of P. shtockmani is almost certainly drawn incorrectly (Kudinova- Pasternak 1990: fig. 3)—the three proximal-most setae on article-3 belong instead to article-2.