Pilbaraxius, Poore & Collins, 2009

Poore, Gary C. B. & Collins, David J., 2009, Australian Axiidae (Crustacea: Decapoda: Axiidea), Memoirs of Museum Victoria 66 (2), pp. 221-287 : 267-269

Pilbaraxius gen. nov.

Type species. Pilbaraxius kariyarra sp. nov., herein designated.

Diagnosis. Carapace smooth or tuberculate; cervical groove visible laterally over third distance to anterolateral margin. Rostrum acutely triangular, with pair of lateral spines, longer than eyestalks, not depressed below level of carapace, continuous with definite lateral carinae; supraocular spines prominent; lateral carina with 1 spine; submedian carina present, with 1 spine; median carina a weak ridge, unarmed; postcervical carina absent. Abdominal somite 1 pleuron acute; pleuron 2 acute, pleura 3–5 acute, with anteroventral tooth. Eyestalk cylindrical, articulating; cornea weakly pigmented. Antenna, scaphocerite long. Maxilliped 3 exopod not clearly bent at base of flagellum. Pleurobranchs present above pereopods 2–4; podobranchs and arthrobranchs well developed; epipods present on maxilliped 2 to pereopod 4. Pereopods 1 slightly asymmetrical, with propodus flattened; carpus-propodus upper margin unarmed, sparsely setose. Pereopods 3–5 propodi with transverse rows of robust setae; dactyli tapering, with longitudinal row of robust setae. Pleopods 3–5, appendix interna present. Pleopod 1 of male absent. Pleopod 2 of male without appendix masculina.Uropodal endopod without lateral and distolateral spines; exopod with transverse suture. Telson with lateral fixed spines and posterolateral robust setae; apex rounded.

Etymology. Pilbara is the name of the region of North-western Australia close to the type locality of the type species.

Remarks. The problematic generic placement of the type species highlights issues with the family Axiidae . The spinose rostrum, diverging palm and long fingers on the chelipeds and abdominal pleura with prominent ventral spination closely resemble those of Calaxiopsis serrata Sakai and de Saint Laurent, 1989 , a species belong to the “calocaridid” group. The new species differs from all in this group in possessing pleurobranchs and lacking the modified pleopods 1 and 2. The new species also resembles species of Calaxius but these usually have highly setose chelipeds and rows of prominent spines on the upper margin of the chelipeds (as in C. acutirostris redescribed above). Neither of these conditions characterises the new species. In addition, the uropodal endopod is apically rounded and lacking lateral and distolateral spines typical of Calaxius and many other axiid genera. Further, pleopod 2 lacks an appendix masculina, a state seen in few axiids. In summary, a new genus seems warranted.