Leipanthura, Poore, 2009

Poore, Gary, 2009, Leipanthura casuarina, new genus and species of anthurid isopod from Australian coral reefs without a " five-petalled " tail (Isopoda, Cymothoida, Anthuroidea), ZooKeys 18 (18), pp. 171-180 : 173-174

Leipanthura gen. n.

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Diagnosis. Body irregularly darkly pigmented. Pleonites 1–5 together longer than greatest width, fused, suture between pleonites 1 and 2 visible only laterally; pleotelson without indication of posterior margin of pleonite 6. Antenna 2 flagellum of 6 articles, longer than article 5 of peduncle. Maxillipedal endite absent; palp articles 1–5 fused. Pereopod 1 propodus cylindrical, not in contact with merus. Pereopods 4–6 carpus with upper margin nearly as long as lower margin, distal margin transverse and without distal lobe, without robust setae on lower margin or on distal angle. Pereopod 7 absent. Uropodal exopod cylindrical, articulating distally in same horizontal plane as endopod.

Type species. Leipanthura casuarina , new species, here designated.

Etymology. Anthura , from Greek anthos, a flower, and oura, a tail, describes the telson and uropods of Anthura gracilis “… which, when alive, much resemble a fivepetaled flower …” ( Leach 1814). Greek leipo, meaning to be without, reflects the absence of the anthuroid tail in this monotypic genus.

Remarks. Several features place this enigmatic new genus well within the family Anthuridae . Th e overall narrow body form, arrangement of pereonites, short antennal flagella, compact mouthparts, simple pereopods with few robust setae, fused pleonites, operculiform first pleopodal exopods, and pleotelson with paired statocysts are typically anthurid. The species is notable within Anthuridae for the absence of pereopod 7 in an adult female. Th e observation that the holotype bears oostegites confirms that this is a neotenous characteristic (all isopods hatch without pereopods 7, this stage being called the manca). Th e condition is seen in one other anthurid, Exallanthura Kensley, 1980 , four genera of Paranthuridae Menzies & Glynn, 1968 ( Poore 1984 2001) and Curassanthura Kensley, 1981 in Leptanthuridae Poore, 2001 ( Wägele 1982) . Exallanthura also shares with Leipanthura a completely fused maxillipedal palp but differs in having a well developed anterodorsal uropodal exopod, more swollen pereopod 1 propodus and a mandibular palp of one article. The only species, Exallanthura sexpes Kensley, 1980 , is known from only two individuals that may be mancas; as is commonly the case with specimens of anthurids they lack features that would identify them as fully developed males (multiarticulate antenna 1) or females (oostegites). Ptilanthura Harger, 1878 has a similar uropod, mandibular palp, maxilliped and pereopod 1 to Exallanthura but examples possess pereopod 7 ( Kensley 1996).

Leipanthura shares fused maxillipedal palp articles with one other genus, Anthura Leach, 1814 , which is a monotypic genus also with pigmented integument. Anthura gracilis Montagu, 1808 has a typical anthuroid uropod, swollen pereopod 1 propodus with a toothed palm, and long pleotelson ( Wägele 1980).

The flattened uropodal peduncle and its almost cylindrical rami that characterise the new genus are unique within Anthuroidea and must be regarded as a reversal to the form seen in Gnathiidae , the probable sister taxon of Anthuroidea ( Brandt and Poore 2003; Cohen and Poore 1994). Placing the genus outside Anthuroidea demands numerous convergences in many other characters.