Koremasphaera, Bruce, 2003

Bruce, N. L., 2003, New genera and species of sphaeromatid isopod crustaceans from Australian marine coastal waters, Memoirs of Museum Victoria 60 (2), pp. 309-369 : 339-340

Koremasphaera gen. nov.

Type species. Koremasphaera colonus sp. nov., here designated.

Diagnosis. Pleotelson posterior margin entire, without ventral exit channel. Dorsal surfaces of pereonites 2–7, pleon and pleotelson densely setose. Pleon with 4 segments, sutures running to lateral margin. Antennule peduncle article 1 more than twice as long as article 2, articles 1 and 2 robust; article 3 slender, all articles collinear. Maxilliped palp articles 2–4 each with distomesial angle strongly produced, those of 3–4 finger-like; article 5 elongate and finger-like; mesial margins with numerous long simple setae. Pleopods 4 and 5 without thickened folds or ridges. Uropods attached subdistally on pleon, both rami semicylindrical in section, apically acute, exopod apex with cuticular spike; pleotelson posterior margin entire.

Description of male. Body stout, about twice as long as greatest width, strongly vaulted; dorsal surface granular, with abundant setae. Head weakly immersed in pereonite 1. Eyes small, facets distinct. Pereon segments with raised posterior margins. Coxae distinctly demarcated, overlapping anterior over posterior, ventrally directed. Membrana cingula absent. Pleon of 4 segments, segment 1 largely concealed by pereonite 7, segments 2–4 indicated by 2 distinct suture lines running to lateral margins of pleon. Pleotelson posterior margin entire without distinct ventral exit channel. Pleonal sternite absent.

Antennule and antenna anteriorly positioned on head. Antennule peduncle articles 1 and 2 robust, article 1 more than twice as long as article 2; article 3 slender, all articles collinear; flagellum about as long as peduncle, extending to middle of pereonite 1. Antenna peduncle articles 1–2 short, subequal, shorter than 4–5, which become progressively longer; flagellum shorter than peduncle, extending to posterior of pereonite 1.

Epistome anteriorly narrowly rounded, apex overlapped by rostrum, medial constriction not present. Labrum unornamented. Mandible incisor multicuspid; molar process prominent, crushing, provided with marginal scale teeth; left mandible with prominent lacinia mobilis both mandibles with spine row of 5 or 6 spines; palp article 1 longer than articles 2 and 3. Maxillule lateral lobe with about 13 RS on gnathal surface, most of which are serrate; mesial lobe with 4 long RS, 3 of which are prominently serrate, and 2 short acute simple RS. Maxilla with all articles well developed; lateral and middle lobes with flat strongly curved and finely serrate RS, mesial lobe with several acute long RS, some of which are basally CP. Maxilliped endite distal margin numerous long acute CP setae and 3 long CP RS on distomesial margin; palp articles 2–4 with distomesial angle strongly produced, that of articles 3–4 finger-like, article 5 elongate and finger-like; mesial margins with numerous long setae, lateral margins of articles 2 and 3 without setae, article 4 with 1 distal seta.

Pereopods all ambulatory, robust; pereopods 1–3 subsimilar, more robust than 4–7; inferior margins of merus, carpus and propodus with serrate and CP RS; setulose fringe weakly developed; dactylus with prominent simple secondary unguis and 2 flattened setae arising at lateral margin, 2 flat setae at distolateral margin. Pereopods 6 and 7 inferior and distal margins of merus, carpus and propodus with numerous serrate and biserrate RS.

Penes paired, adjacent; short, about twice as long as basal width; not reaching pleopod peduncles.

Pleopods 1–3 both rami with PMS. Pleopod 1 exopod distal margin subtruncate, proximolateral angle with single short acute RS; endopod distinctly triangular in shape. Pleopod 2 with appendix masculina basally attached on mesial margin. Pleopod 3–5 exopods with complete suture. Pleopods 4 and 5 exopod and endopods without transverse thickened ridges; pleopod 5 endopod with 2 scale patches. Uropod attached in ventromesial position; both rami subcylindrical in section, subequal in length; both rami narrowing evenly to an acute apex, not extending significantly beyond posterior margin of pleotelson, exopod distally with hardened spike.

Female. Similar to male; brood-pouch unknown.

Etymology. From Greek korema (brush), coupled with the ending - sphaera to indicate family affinity; alluded to the densely setose dorsal surfaces (feminine).

Remarks. Koremasphaera is another monotypic genus difficult to characterise and define but its species defies placement in any existing genus. The most similar genera are Cymodoce Leach, 1814 and Oxinasphaera Bruce, 1997 , both large genera. Oxinasphaera is unambiguously defined, the principle diagnostic apomorphic characters being the antennule peduncle spikes, epistome and pereon with cuticular spikes, and the short uropod exopod with a deeply bifid apex, all of which are absent in Koremasphaera . In addition Oxinasphaera usually has an excavate pleotelson posterior margin. Points of similarity include the very long finger-like prolongation of the mesial lobes of the mandible palp articles 3, 4 and 5, the penial morphology and the presence of weakly developed spikes on the pleon and pleotelson. Cymodoce is less similar, and differs in the pleotelson having an excavate posterior margin, in having both uropod rami lamellar (European species) or the exopod only lamellar (Indo-Pacific species; Bruce, 1997), slender and elongate penial processes, and in having the posterior of the pleotelson with a prominent dorsal hardened hemispherical medial dome.

The characters which serve to identify Koremasphaera are the densely setose dorsal body surfaces; the posterior margin of the pleotelson entire; uropod rami thickened and terminally acute; penial processes short, wide and adjacent; maxilliped palp articles 3–5 strongly produced and provided with long setae; and pleopods 4 and 5 without thickened folds or ridges. Uropod morphology in Sphaeromatidae is consistent within genera, at least when monophyly seems assured (e.g. Sphaeroma and Oxinasphaera ) and the uropods of Koremasphaera , with both rami semicylindrical and apically acute and subequal in size, are unique and a putatives synapomorphy.