Pilbarana grandis Stringer & King sp. nov.

(Figs. 2–4)

urn:lsid:zoobank.org:act: D7C6FEE5-FF95-49BB-83FB-47875CC57A15

Material examined. Holotype: male, WAM C78830 (RL1779), Cork Tree Well, Cane River Conservation Park, WA, 22°21′22.0ʺS 115°30′35.4ʺE, coll. R. Leijs and R. A. King, 28 June 2011. Paratypes: 3 males, 1 female, 1 juvenile, WAM C78831 (RL1779; GenBank COI: OK170022, OK170023), collection data as for holotype; 1 male, WAM C78832 (RL1750), Cork Tree Well, Cane River Conservation Park, WA, 22°21′22.0ʺS 115°30′35.4ʺE, coll. R. Leijs and R. A. King, 24 June 2011.

Diagnosis. Head with antennal sinus square-shaped. Antenna 1 peduncular article 1 approximately equal in length to article 2. Antenna 2 peduncular articles 4–5 distinctly longer than length of head; flagellum shorter than peduncular article 5. Gnathopod 1 propodus approximately 2.5 times as long as broad; carpus greater than 4 times as long as broad. Pereopods 3–4 coxae with small anterior lobe. Uropod 1 peduncle with two or more robust basofacial setae. Uropod 2 peduncle similar in length to inner ramus.

Description. Holotype male. Length 7.0 mm. Head (Fig. 2A) with antennal sinus square-shaped, anteroventral corner rounded. Antenna 1 (Fig. 2B) peduncular article 1 approximately equal in length to article 2; peduncular article 3 around one third length of article 2; primary flagellum of 16 articles, with one ventral aesthetasc on proximal margin of most articles. Antenna 2 (Fig. 2C) slender, around two thirds length of antenna 1; peduncular article 4 approximately equal in length to peduncular article 5, both articles each longer than length of head; flagellum of 7 articles, shorter than peduncular article 5. Mandible (Fig. 2D) palp article 1 twice as long as broad, around half length of articles 2 and 3, articles 2 and 3 approximately equal in length. Maxilla 1 (Fig. 2E) outer plate with seven denticulate robust setae. All other mouthparts (Figs. 2F, G) as in generic description.

Gnathopod 1 (Fig. 3A) coxa anteriorly projected with one associated seta, posterodistal corner reduced and somewhat concave; propodus approximately 2.5 times as long as broad; carpus greater than 4 times as long as broad. Gnathopod 2 (Figs. 2A, 3B) coxa anteriorly projected with associated seta, propodus approximately 2 times as long as broad. Pereopods 3–4 (Figs. 3C, D) coxae with small anterior lobe and associated setae. Pereopods 5–7 (Figs. 2A, 3E–G) coxae anterior lobe gradually less distinct (coxae 5–6 lobe with associated seta), posterior lobe very small.

Uropod 1 (Fig. 4A) peduncle with two robust basofacial setae, row of robust setae along dorsal margin. Uropod 2 (Fig. 4B) peduncle similar in length to inner ramus, row of setae along dorsal margin. Uropod 3 (Fig. 4C) outer ramus cylindrical with 2 articles, first article approximately 1.6 times length of second article.

Distribution. Cane River Conservation Park, Ashburton River Basin, Pilbara, Western Australia.

Etymology. This species name is taken from the Latin word ‘grandis’, and refers to the large body size of this and other species of Pilbarana.

Remarks. Overall, the two new species of Pilbarana can be distinguished morphologically based on the shape of the antennal sinus, the length and elongation of antennal articles, differences in the shape of coxae, the length of the first gnathopod propodus, the number of robust basofacial setae on the peduncle of the first uropod, and the length of the peduncle of the second uropod versus the length of the rami. Examination of specimens of P. grandis sp. nov. has revealed that individuals may possess between two (most common) and four robust basofacial setae on the peduncle of the first uropod, with the number of basofacial setae further fluctuating, in some cases, between the pair of uropods for a single specimen. Specimens (except for juveniles), nonetheless, never possess only a single basofacial seta, contrasting with specimens of P. lowryi sp. nov. that always exhibit only one robust basofacial seta on the peduncle of the first uropod. The number of robust basofacial setae on the peduncle of uropod 1 is one of the few morphological characters that separate distinct lineages of Nedsia from the Pilbara (King et al. 2022) and, consequently, appears to represent a useful and consistent distinguishing eriopisid trait.

Molecular analyses further revealed that the two new species of Pilbarana are highly divergent genetically, with approximately 13–14.5% COI divergence estimated (with 0.2% between sequences of P. grandis individuals). This level of divergence is well above the 5–10% threshold principally followed by King et al. (2022) in their description of new Nedsia species, and is indicative of long-term isolation in discrete (and distant) subterranean habitats. Pilbarana grandis has, thus far, only been sampled from one well in the Cane River Conservation Park in the Pilbara region and is located approximately 250 km from bores in the Fortescue Basin where P. lowryi was collected (Fig. 1).