Pilbarana Stringer & King, 2022

Stringer, Danielle N., King, Rachael A., Austin, Andrew D. & Guzik, Michelle T., 2022, Pilbarana, a new subterranean amphipod genus (Hadzioidea: Eriopisidae) of environmental assessment importance from the Pilbara, Western Australia, Zootaxa 5188 (6), pp. 559-573 : 562-563

Pilbarana Stringer & King gen. nov.

urn:lsid:zoobank.org:act:39BF6911-DFF8-440F-B4BB-3DDA3E0DD75D

Type species: Pilbarana grandis sp. nov.

Included species: Pilbarana grandis sp. nov. and Pilbarana lowryi sp. nov.

Diagnosis. Head with weakly concave antennal sinus.Antenna 1 not longer than half body length. Maxilla 1 inner plate with one distal robust seta. Coxae reduced, with coxae 1–4 lengths (depths) distinctly shorter than pereonite lengths; coxae 1–2 anteriorly projected/produced, coxae 3–4 with small to indistinct anterior lobe and associated seta(e), posterior lobe indistinct, coxae 5–7 with anterior lobe gradually less distinct (coxae 5–6 anterior lobe with associated setae), posterior lobe very small. Coxal gills present on coxae 3–6, sternal gills absent. Pereonite 1 with concave posterodistal corner; pereonites 2–7 laterally square-shaped, as broad as long, vermiform body shape. Gnathopod 1 carpus at least 3.5 times as long as broad, longer than propodus; propodus with palm distinctly transverse. Gnathopod 2 propodus approximately 4.5 times length of carpus, palm enlarged, strongly oblique. Pereopods 5–7 basis not distinctly expanded posteriorly, pereopod 7 without lobe on posterodistal corner. Uropod 1 peduncle 2 times length of rami, with one or more robust basofacial seta(e). Uropod 3 strongly extended, distinctly larger than uropod 1; outer ramus cylindrical, larger than inner ramus and apically concave.

Description. Head with rostrum weak to obsolete; lateral cephalic lobes moderately to strongly projecting, broad, antennal sinus present, weakly concave; eyes absent. Antenna 1 not longer than half body length; longer than antenna 2; flagellum about 1.2 times length of peduncle; accessory flagellum of two articles, second article tiny. Antenna 2 flagellum shorter than peduncle; calceoli absent. Mandible palp of three articles, terminal article linear or tapered with long apical setae; molar small and triturative. Maxilla 1 inner plate ovate with one distal robust seta; outer plate with denticulate robust setae; palp of two articles. Maxilla 2 inner plate with row of simple and plumose apical setae. Maxilliped inner and outer plates moderately setose, outer plate with smooth edge (not serrated as in Nedsia ).

Coxae 1–7 short, broader than long with few or no posterior setae; coxae 1–4 lengths (or depths) distinctly shorter than pereonite lengths; coxae 1–2 anteriorly projected/produced, coxae 3–4 with small to indistinct anterior lobe and associated seta(e), posterior lobe indistinct, coxae 5–7 with anterior lobe gradually less distinct (coxae 5–6 anterior lobe with associated setae), posterior lobe very small; coxae 3–6 with simple ovate gills, coxa 6 gill smallest; coxae 2–5 with thin, poorly setose oostegites. Thoracic segments lacking sternal gills. Pereonite 1 with concave or ‘cut out’ posterodistal corner; pereonites 2–4 with distinctly lobed posterodistal corners; pereonites 5–7 slightly lobed at posterodistal corners with associated setae. Gnathopods 1–2 subchelate, not sexually dimorphic. Gnathopod 1 decidedly smaller than gnathopod 2; carpus at least 3.5 times as long as broad, with multiple rows of setae, longer than propodus; propodus with palm distinctly transverse with two robust setae at palm corner. Gnathopod 2 carpus much shorter than propodus, similar length to merus; propodus approximately 4.5 times length of carpus, with palm enlarged, strongly oblique, with robust setae, including one long robust seta, at palm corner and along palm margin. Pereopods 3–4 similar, basis not expanded posteriorly. Pereopods 5–6 basis with slight posterior expansion, remaining longer than broad, small lobe on posterodistal corner. Pereopod 7 longer than pereopods 5–6; basis longer than broad, not expanded posteriorly, no lobe present on posterodistal corner.

Epimera 1–3 with serrated or sculptured posterodistal corners and associated setae. Epimera 2–3 ventral margin with central seta. Uropod 1 peduncle approximately 2 times length of rami, with one or more robust basofacial seta(e). Uropod 2 smaller than uropod 1; outer ramus shorter than inner ramus. Uropod 3 strongly extended, not sexually dimorphic, distinctly larger than uropod 1, parviramous; outer ramus cylindrical with two articles, second article apically concave; inner ramus short and scale-like. Telson longer than broad, deeply cleft into two lobes, with lateral setae and long apical penicillate setae.

Etymology. The name Pilbarana references the Pilbara region of Western Australia where this genus is found. The gender should be considered as female.

Remarks. Pilbarana gen. nov. was placed within Eriopisidae by King et al. (2022, labelled ‘ Eriopisidae gen. undet.’) as a reciprocally monophyletic lineage based on COI mtDNA and 28S rRNA molecular data and due to the presence of eriopisid morphological characters: biramous and enlarged third uropod, one or multiple robust basofacial seta(e) on the peduncle of the first uropod, the lack of sternal gills, and the absence of sexually dimorphic second gnathopods ( Lowry & Myers 2013). King et al. (2022) further indicated that Pilbarana , together with Nedsia and Norcapensis , the two additional WA subterranean eriopisid genera, are genetically divergent from the morphologically similar Australian melitid genera, Brachina Barnard & Williams, 1995 and Nurina Bradbury & Eberhard, 2000 , supporting the current morphological-based classification of Lowry & Myers (2013).

Morphologically, Pilbarana is expectedly more similar to Nedsia and Norcapensis than any of the east coast Australian marine and estuarine eriopisid genera: Eriopisella Chevreux, 1920 , Netamelita J. L. Barnard, 1962 , and Victoriopisa Karaman & Barnard, 1979 . It appears to be closest to Norcapensis particularly due to the larger body size compared to Nedsia , a mandible palp of three articles, similarly enlarged second gnathopods, and strongly extended, cylindrical third uropods. Pilbarana , however, can be easily differentiated since Norcapensis : lacks an antennal sinus; comprises an elongate first antenna, reaching past half body length; maxilla 1 inner plate consists of a row of distal plumose setae; possesses a markedly robust rather than vermiform body shape with the first pereonite lacking a distinctly concave or ‘cut out’ posterodistal corner and pereonites 2–7 around 2 times as long as broad; comprises coxal gills on coxae 2–6; first gnathopod with carpus equal in length to propodus; pereopods 5–7 bases progressively more expanded posteriorly; uropod 1 peduncle is approximately equal in length to rami; and uropod 3 outer ramus second article is not apically concave. Pilbarana is, additionally, distinct from Nedsia as Nedsia , like Norcapensis , lacks an antennal sinus and possesses elongated first antennae, but further consists of comparably smaller second gnathopods, and third uropods that are leaf-shaped rather than cylindrical.