Pentaceration omalos Just, 2011, sp. nov.
Creators: name: Just, Jean
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Paramunnidae
Pentaceration
Pentaceration omalos

description: Pentaceration omalos sp. nov.
Figures 8–9
Type fixation. Holotype, male, here designated.
Etymology. The epithet is the Greek adjective ομαλος (omalos = smooth) indicating that head and pereonite spines are smooth, at most with a slightly rough cuticle.
Material examined. Holotype, 3, 2.35 mm, Australia, Tasmania, off Freycinet Peninsula, 42o0.20'S, 148o37.70'E, 720 m, coarse shelly sand, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 46, NMV J20052 (with 2 slides).
Paratypes (27 specimens). Australia, New South Wales, off Nowra, 34o57.90'S, 151o8.00'E, 503 m, Bryozoa and shell, WHOI epibenthic sled, G.C.B. Poore et al, RV Franklin, 14 July 1986, stn SL 2, NMV J20049 (2 ovigerous Ƥ). Australia, Tasmania, off Freycinet Peninsula, 42o0.20'S, 48o37.70'E, 720 m, coarse shelly sand, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 46, NMV J20050 (14 Ƥ). Australia, Tasmania, off Freycinet Peninsula, 42o0.20'S, 148o37.70'E, 720 m, coarse shelly sand, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 46, NMV J20051 (1 3). Australia, Tasmania, off Freycinet Peninsula, 42o0.20'S, 148o37.70'E, 720 m, coarse shelly sand, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 46, NMV J20053 (1 small 3). Australia, Tasmania, off Freycinet Peninsula, 41o58.60'S, 148o38.80'E, 500-600 m, coarse shell, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 47, NMV J20054 (2 ovigerous Ƥ). Australia, Tasmania, off Freycinet Peninsula, 41o57.50'S, 148o37.90'E, 400 m, coarse shell, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL 48, NMV J20055 (1 Ƥ, 1 small 3). Australia, Victoria, 70 km S of Gabon Island, 38o10.3'S, 149o57.2'E, 592 m, WHOI epibenthic sled, R.S. Wilson, FRV Sola, 14 October 1984, stn BSS 227, NMV J20056 (4 ovigerous Ƥ). Australia, New South Wales, off Nowra, 34o54.68'S, 151o11.36'E, 800–850 m, 5 m otter trawl, M.F. Gomon et al, RV Franklin, 15 July 1986, stn SL 5, NMV J20057 (1 3).
Description (male, holotype). Body, elongate with nearly parallel pereon sides; width 0.3 length, widest between pereonites 2 and 3. Head length 0.28 width, length posterior to eyestalks 1.5 anterior length. Frontal margin mid-spine length equals combined mid length of pereonites 2–5, slender, pointed; lateral spines approximately one third longer than mid spine, otherwise similar, diverging at 115°. All 3 head spines tending to turn upward in distal half. Eyestalks overreaching lateral spines on pereonite 1 by approximately 0.25 eyestalk length, pointing forward at 10º to head midline, tapering to acute point.
Pereonites 1–7 with single middorsal slender, upright spine arising from broad base, all of subequal length. Pereonite 1 lateral margins convex with short, triangular spine in posterior half, pointing forward; pereonites 2–3 with slender acute lateral spines, diverging at 25° from each other, similar to lateral head spines, pereonite 2 spines approximately as long as 0.75 pereonite width, pereonite 3 spines 0.5 pereonite width; pereonite 4 lateral spines approximately as long as, but much more slender, than on pereonite 1; pereonites 5 lateral spines similar to 4 but slightly longer; spines on 6 the longest, approximately 1.2 length of pereonite 2 spines, pointing backwards at approximately 60° to body mid-line; pereonite 7 lateral spines slightly longer and stouter than on pereonite 5, pointing backwards at approximately 30º (left side; right side appears damaged).
Pleon length 1.86 width. Pleonite 1 width equals distance between uropods, length 0.15 width. Pleotelson with short proximal neck; proximal and lateral margins merging evenly, lateral margins evenly convex, with 7–8 denticles; distal projection drawn out to long, pointed spine, approximately 0.5 length of entire pleotelson.
Antennula articles 1 and 2 combined reaching well beyond apex of eyestalks; article 1 shorter and slightly wider than 2, tubular; 3 and 4 of equal length, combined approximately 0.7 length of 5; 6 length 0.85 of 5. Antenna article 2 in ventral view 3.3 length of 1,with medial bulge in proximal half; article 3 width 0.20 length; article 5 length 4.0 times 4; 6 length 1.5 times 5; flagellum with 9 articles, proximal article length subequal to combined 2 and 3 length.
Pereopod I basis length 4.8 times width, anterodistal margin with long row of small acutely pointed spines; ischium length 0.63 length of basis, length 4b times width; carpus narrowly oval, posterior margin with small translucent flanges at base of robust setae; propodus narrowing distally to insertion of dactylus, with 2 robust setae on opposing margin. Pereopods II–VII slender, basis of 2 and 3 with row of small spines similar to pereopod I; propodus Pereopods II and III with 2 slender robust setae on posterior margin, of pereopod VI with 4 robust setae.
Pleopod I distal lateral sublobe prominent, broadly rounded, overlapping smaller, triangular proximal lobe; width 0.27 distance to midline; distal projection length 0.38 pleopod total length, forming acute angle, with bluntly pointed apices. Pleopod II protopod rounded distally, lateral margin with simple setae; endopod article 2 (stylet) forming approximately 125° curve.
Uropods recessed into simple cuticle fold; protopod and exopod apparently absent; endopod length 3 times width.
Female. Females have slightly less strongly developed pereonite 1 lateral parts, but are otherwise similar to males (assuming that the holotype male is not fully terminal: pereopod I). The operculum is ovoid, pointed with nearly straight distal margins, width 0.68 length.
Size. Largest male, 2.35 mm; largest ovigerous female, 2.80 mm.
Distribution. Australia, eastern Bass Strait slope to eastern Tasmania, 400– 850 m.
description: Published as part of Just, Jean, 2011, Remarkable Australasian marine diversity: 18 new species in Pentaceration Just, 2009 (Crustacea, Isopoda, Paramunnidae), pp. 1-54 in Zootaxa 2813 on pages 13-16, DOI: 10.5281/zenodo.203856