Palabriaphoxus Gurjanova, 1977

Taylor, Joanne & Peart, Rachael A., 2023, A New Genus and Five New Species of Phoxocephalidae (Crustacea: Amphipoda) from the Eastern Tasman Sea, the Otago Shelf, and The Snares, New Zealand, Records of the Australian Museum (Rec. Aust. Mus.) 75 (4), pp. 567-600 : 568-569

Palabriaphoxus Gurjanova, 1977

Palabriaphoxus Gurjanova, 1977: 74 .—Barnard & Karaman, 1991: 623.

Type species. Harpinia palabria J. L. Barnard, 1961 , original designation.

Diagnosis of female. Rostrum fully developed, unconstricted (tapering abruptly in P. barnardi sp. nov.). Eyes absent (tiny–small in P. lowryi sp. nov.). Antenna 1 peduncle article 2 variable in length, ventral setae narrowly to widely spread, placed apically or in middle. Antenna 2 peduncle article 1 not ensiform (weakly so in P. barnardi sp. nov.); article 3 with 2–5 setae; facial slender and robust setae on article 4 in 1 main row or clump or 2 or more poorly defined rows; article 5 especially short. Prebuccal parts not extended forward, truncate, not strongly distinct, neither part dominant. Right mandibular incisor with 3 teeth; molar not trituritive, small, pillow shaped, with 3 or fewer splayed, diverse, articulate to semiarticulate robust setae, palpar hump medium; right lacinia mobilis either absent or bifid, asymmetrical, (subflabellate in P. lowryi sp. nov., flabellate in P. palabria ), mandibular palp thin to medium, article 1 short (slightly elongate in P. palabria ), article 2 without outer setae (single outer setae in P. latifrons ), apex of article 3 oblique. Maxilla 1 palp 2-articulate, inner plate with 4 setae, outer plate with 9–11 setal teeth, 1 setal tooth especially thickened. Maxilliped inner plates not basally fused, palp article 3 apex not protuberant, dactylus weakly to strongly elongate, apical nail distinct, elongate. Gnathopods small to medium, similar to diverse, gnathopod 2 not or weakly enlarged; carpus of gnathopods 1–2 short to medium, free (gnathopod 2 cryptic in P. lowryi sp. nov.), palms oblique, propodi ordinary to almond shaped, weakly elongate, not or poorly setose anteriorly. Pereopod 5 basis, merus and carpus narrow. Pereopod 6 merus and carpus broadened. Pereopod 7 basis without facial setae, weakly to strongly setose and moderately to strongly toothed posteroventrally, ischium enlarged, merus ordinary, (strongly lobed in P. lowryi sp. nov). Epimeron 1–2 with medium posterior setae, without midfacial setae above ventral edge. Epimeron 3-setose ventrally and facially (weakly in P. barnardi sp. nov.), not setose posteriorly, with large posteroventral tooth (elongate in P. lowryi sp. nov). Urosomite 3 without dorsal hook or special process. Uropod 1 peduncle without basoventral setae, without dorsolateral robust setae (present in Palabriaphoxus barnardi sp. nov.), outer ramus medium (shortened in P. lowryi sp. nov.), inner ramus with robust setae on dorsolateral and dorsomedial margins (barely 2 rows in P. barnardi sp. nov.), rami variously spinose. Uropod 2 peduncle with only 1 medial (sometimes enlarged) simple or robust seta confined apically, inner ramus ordinary (reduced in P. palabria ), peduncle apices of uropods 1–2 not combed. Uropod 3 peduncle lacking extra subapical slender or robust setae, article 2 of outer ramus short to medium, without setae or carrying elongate apical setae. Telson with pair of midlateral or dorsal setules on each side, with 1–4 apical setae on each lobe. Six pairs of gills.

Sexual dimorphism. Antenna 1 peduncle articles 1–3 without patch of fine setae in males; primary flagellum with callynophore. Calceoli absent or present on peduncle of male antenna 2 (male unknown in P. barnardi sp. nov.). Antennae 1–2, flagella unreduced in female.

Remarks. Two new species from the Tasman Sea belonging to the subfamily Harpiniinae are described. The generic placement according to Barnard & Karaman (1991) is not straightforward for either Palabriaphoxus barnardi sp. nov. or P. lowryi sp. nov. as the diagnoses and keys rely heavily on the morphology of male antenna 2, which is unknown in the former. Both new species have a combination of morphological characters that could justify their placement in several of the genera that exhibit a narrow basis of pereopod 5. The preliminary morphological phylogeny of Taylor (2003) places both new species in a clade with representative species of seven genera that share a single strict synapomorphy (narrow basis of pereopod 5). The suggestion that several genera belonging to the Harpiniinae could potentially be synonymized into a single genus Harpinia was proposed by Karaman (1980) and Taylor (2003), but not until such time that all known species were included in the phylogeny as it was acknowledged that the structure of the tree may change with their inclusion. A further attempt to resolve the structure within the subfamily Harpiniinae using both morphology and the CO1 gene sequences was undertaken by Spencer (2022) and preliminary results also suggest a revision is required as not all genera are supported and the monophyly of the Harpiniinae is questioned. Options currently available for placement of these two new species from New Zealand are: 1) erect two new monotypic genera based on the recombination of known character states; 2) synonymize multiple genera with narrow basis of pereopod 5; or 3) placement in an existing genus that can be best expanded to include the new taxa. Owing to their morphological similarity to Palabriaphoxus palabria (J. L. Barnard, 1961) (the type species of Palabriaphoxus ), also known from the Tasman Sea, we redescribe this genus to accommodate the two new species. Characters that the four known species of Palabriaphoxus share include: antenna 2 flagellum of female multiarticulate; right mandibular incisor with 3–4 teeth, mandibular molar non-trituritive, reduced to a small hump, maxilla 1 palp 2-articulate, gnathopod 1–2 similar in size (gnathopod 2 slightly enlarged in Palabriaphoxus lowryi sp. nov.), pereopod 5 basis of narrow form, pereopod 6 greatly enlarged with thickened merus-propodus, pereopod 7 usually with enlarged ischium.

Key to world species of Palabriaphoxus

1 Posteroventral corner of coxae 1–3 with prominent extended acute tooth .................................................. [Antarctic; 180–1098 m] ........... Palabriaphoxus latifrons

—— Posteroventral corner of coxae 1–3 smooth or with reduced small acute tooth ............................................................................. 2

2 Uropod 1 peduncle without enlarged robust setae. Antenna 1 peduncle article 2 setae placed distally. Antenna 2 peduncle article 3 with 5 stiff robust setae. Pereopods 3–4 carpus setae displaced and dispersed near posterior margin. Rami of uropods 1–2 never fully spinose; uropod 2 peduncle with with robust setae only ... [Tasman Sea & The Snares; 7–133 m] .. Palabriaphoxus lowryi sp. nov.

—— Uropod 1 peduncle with enlarged robust setae. Antenna 1 peduncle article 2 setae placed in middle. Antenna 2 peduncle article 3 with 2 stiff robust setae plus setule. Pereopods 3–4 carpus setae placed near anterodistal margin. Uropods 1–2 rami with robust setae; uropod 2 peduncle with mixture of robust and slender setae ......................................................... 3

3 Antenna 1 peduncle article 2 elongate. Antenna 2 peduncle article 4 elongate. Maxilla 1 outer plate with 11 robust setae. Gnathopod 2 enlarged, slender seta forming dominant posterior element on pereopods 3–4 carpus. Urosome with basoventral setae. Telson with lateral robust setae. Epimera 1–2 with facial setae ................................... [circum-New Zealand; 10–610 m] ........... Palabriaphoxus palabria

—— Antenna 1 peduncle article 2 shortened. Antenna 2 peduncle article 4 shortened. Maxilla 1 outer plate with 9 robust setae. Gnathopod 2 not enlarged, robust setae forming dominant posterior element on pereopods 3–4 carpus. Urosome without basoventral setae. Telson without lateral robust setae. Epimera 1–2 without facial setae ........................ [Tasman Sea; 520 m] .................. Palabriaphoxus barnardi sp. nov.