Joeropsididae Nordenstam, 1933

Bruce, Niel L., 2015, Joeropsididae Nordenstam, 1933 (Crustacea, Isopoda, Asellota) from the Lizard Island region of the Great Barrier Reef, Queensland, Australia, ZooKeys 491, pp. 1-62 : 4-6

Taxon classification Animalia Isopoda Joeropsididae

Family Joeropsididae Nordenstam, 1933

Jaeropsinae Nordenstam, 1933: 190.

Iaeropsinae. - Nierstrasz 1941: 288.

Jaeropsidae . - Menzies 1962: 63. - Menzies and Glynn 1968: 75.

Joeropsididae . - Sivertsen and Holthuis 1980: 96. - Wilson 1997: 86. - Kussakin 1999: 10. - Just 2001: 303.

Diagnosis.

Male. Body dorsoventrally flattened; lateral margins normally parallel, occasionally tapering posteriorly. Pereonites of subequal length; lateral margins covering coxae in dorsal view, entire, smooth or finely serrate. Pereopods all ambulatory, all similar; pereopod 1 with 2 dactylar claws, pereopods 2-7 with 2 or 3 dactylar claws. Eyes dorsolateral, sessile. Anterior margin of cephalon with strong median concavity. Pseudorostrum present, inserted into cephalic concavity, rarely joined along straight line. Pleon with no free pleonites. Pleotelson subequal in width to pereonite 7. Anten na 1 shorter than cephalon, peduncular article 1 expanded, longer than articles 2 and 3 combined; flagellum shorter than peduncle, with 3-5 articles. Antenna 2 peduncle geniculate, with article 6 and flagellum folding laterally and posteriorly under lateral margin of expanded article 5; first 4 articles short, article 4 more or less embedded into 3, article 5 longer than 1-4 combined, expanded laterally, article 6 0.5-0,8 as long as article 5, generally widening distally; antennal scale absent; flagellum with enlarged, normally conjoint article 1. Mandible molar a long, slender, pointed projection (often with small accessory denticles); incisor of 4-6 large teeth; lacinia mobilis absent; spine row present. Maxilliped sub-quadrate, covering entire mouthpart field, distally margin convex, with distinct distomesial concavity; palp with at least article 2 mesially expanded, epipod half length of endite or less. Pleopod 2 rami with longer or shorter lateral fringe of modified cuticular scales. Pleopod 3 exopod biarticulate, longer than endopod, with lateral fringe of modified cuticular scales; endopod with 3 plumose setae. Pleopod 4 exopod vestigial. Uropods biramous, inserted ventrally on pleotelson usually within distinctive insinuation in pleotelson margin; peduncle broader than long and mesially expanded; rami shorter than peduncle. Anus outside pleopodal chamber, between bases of uropodal peduncles, partly or entirely covered by pleopod 1.

Female. Pleopod 2 with lateral fringe of cuticular scales; partly or entirely covering anus. Female spermathecal duct opening on anterior surface of pereonite 5, oviduct opening ventrally on pereonite 5 mesially to coxa. Oostegites on pereopods 1-5.

Included genera.

Joeropsis Koehler, 1885, Rugojoeropsis Just, 2001 and Scaphojoeropsis Just, 2001.

Remarks.

Only a few species of the family Joeropsididae had been described by the 1990s. By 1950 eleven species of Joeropsis had been named, and a further 13 species had been described by 1975. In a period of high activity in the late twentieth century (see Poore and Bruce 2012), notably by Hans-Georg Müller and Brian Kensley, a further 29 species were named (see Schotte et al. 2011), all the while the family remaining with the single genus. In 2001 Jean Just described the first new genera within the Joeropsididae , and at that point there were 69 known species and two subspecies ( Just 2001).

The family is readily recognised, including in the field, by the compact body shape, with a characteristically robust and reflexed antenna 2, and small, ventrolaterally inserted uropods with a peduncle that is large in relation to the tiny rami.

The mouthpart morphology suggests that the highly mobile joeropsidids are carnivorous. The mandibles usually possess a five-cusped incisor with acute cusps, completely lacks a lacinia mobilis, has a prominent spine row of simple or finely serrate spines and a blade-like molar process, all characters that are analogous to the mouthparts of the scavenging or predatory isopod family Cirolanidae . These characters are not unique to the family, but the maxilliped morphology with the large endite, small palp and epipod, and mesially excavate distal margin does appear to be unique.

The phylogenetic relationships of the Joeropsididae remain unsettled. Three analyses have included representatives of the family ( Wilson 1994; Rapuach et al. 2009; Lins et al. 2012) but none had the Joeropsididae as the primary focus. Wil son (1994), using morphological data, included the Joeropsididae as a potential outgroup for the Janiridae , and found that the Joeropsididae was sister to Jaera + Iais (Wilson 2004, figs 1 and 2), but those clades lacked supporting apomorphies. In contrast both Raupach et al. (2009) and Lins et al. (2012), using molecular data, found that the Joeropsididae are closer to the Acanthaspidiidae . Raupach et al. (2009) showed the Joeropsididae as sister group to the Acanthaspidiidae (including Ianthopsis ) and that Joeropsididae + Acanthaspidiidae are sister to Iarthrippa (part of Janiridae ) ( Raupach et al. 2009, fig. 1, strict consensus tree), or sister to Iarthrippa ( Raupach et al. 2009, fig. 2, 50% majority rule tree), with Joeropsididae + Iarthrippa sister to Acanthaspidiidae + Ianthopsis . Lins et al. (2012) found that the Joeropsididae is sister group to the Acanthaspidiidae (Fig. 1). These analyses uphold the monophyly of the Joeropsididae , and indicate a close but unresolved relationship to both the Acanthaspidiidae and Janiridae .

Key to the genera of Joeropsididae