Marmachius, Poore, Gary C. B., 2012

Poore, Gary C. B., 2012, Marmachius, a spectacular new genus of Antarcturidae (Crustacea: Isopoda: Valvifera), Zootaxa 3559, pp. 61-68 : 63

Marmachius n. gen.

Type species. Marmachius fortunae n. sp., by original designation.

Diagnosis. Body weakly geniculate between pereonites 4 and 5, anterior pereon slightly elevated. Head with pair of submedian spines between eyes. Pereonites with supracoxal spines on all pereonites, with paired sublateral spines (exceptionally long), with paired submedian spines (exceptionally long), with middorsal spines on posterior margins of pereonites 1–5. Pleonite 1 free from remaining segments of pleotelson; pleotelson dorsal surface bulbous, differentiated from lateral margin by longitudinal groove; pleonites 5 and 6 with middorsal spines, with paired submedian spines or tubercles, with few pairs of sublateral spines, none more prominent than others, with marginal lateral spines, with prominent paired posterior sublateral spines, with prominent medial posterior spine dorsal to margin. Antenna 2 flagellum of 9 or more short articles. Pereopods 2–4 with regular rows of long setae along flexor margins of merus-propodus; unguis short, curved. Pleopod 1 of male exopod groove opening distolaterally on lobe-like apex beset with numerous fine setae. Pleopod 2 of male, appendix masculina elongate, acute, considerably longer than endopod. Oostegites 2–4 unknown.

Included species. Marmachius fortunae n. sp., Antarcturus princeps Kussakin & Vasina, 1998 .

Etymology. For friend and fellow traveller Michael Marmach, whose carefully prepared 35-mm photographs of crustaceans revealed their hitherto hidden colours and set Museum Victoria on the road to a web presence.

Remarks. The new genus shares many features with Antarcturus s.s. Both genera have paired submedian spines on the head, sublateral and lateral (supracoxal) spines on all pereonites and lateral spines on the pleotelson. All are much longer in Marmachius than in any species of Antarcturus . Submedian spines are prominent on all segments in Marmachius but are evident only as tubercles in Antarcturus oryx . Both genera possess posterolateral spines on the pleotelson. Only Marmachius possesses middorsal spines, on the posterior margins of pereonites 1–5, on pleonites 5 and 6, and a prominent medial posterior spine dorsal to the margin. Pleonite 1 is free from the remaining pleotelson in Marmachius but not so in Antarcturus . The oblique groove on the male pleopod 1 exopod opens on a distolateral shallow notch in Antarcturus but opens distolaterally on a lobe-like apex beset with numerous fine setae in Marmachius . This structure has not been illustrated as such in any other antarcturid. The figure of the male pleopod 1 of Antarcturus princeps is sufficiently similar and this species is here included in Marmachius . These two species share elongate spines seen elsewhere only in Acantharcturus Schultz, 1981 . The male pleopod 1 of its type species, A. acutipleon Schultz, 1981 resembles that of Marmachius in as far as Schultz’s illustration allows. I have examined his holotype (USNM 181252) but the pleopods are lost. The species also has a free pleonite 1 and middorsal spines on the posterior margins of pereonites 1–5 but not on the pleon. Instead, the pleotelson ends in a strong posterior marginal spine, not a supramarginal one, lacks prominent paired sublateral posterior spines, and is evenly tapering instead of having a bulbous shape distinct from the margin. Acantharcturus also differs in having a shorter antenna 2 flagellum (four articles rather than nine), and having a setiform unguis on pereopods 2–4 rather than a short one.