Stigmops polyvelota, Lillemets & Wilson, 2002

Lillemets, B. & Wilson, G., 2002, Armadillidae (Crustacea: Isopoda) from Lord Howe Island: New Taxa and Biogeography, Records of the Australian Museum 54, pp. 71-98: 75-79

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Stigmops polyvelota


Stigmops polyvelota   n.sp.

Figs. 4–6

Type material. HOLOTYPE Ƌ, P59952 View Materials , 9.0 × 4.9 mm, K&M 28.ii.79   . PARATYPES from K&M 26.iv.79: P59953 View Materials , ♀   , 8.9 × 4.5 mm, mouthparts on SEM stub, colour photograph K.1030; P59955 View Materials   , Ƌ, 3 SEM stubs; P59954 View Materials , ♀   .

Type locality. All specimens collected in pitfall traps on Mount Gower , Lord Howe Island, New South Wales, Australia, 31°35'S 159°05'E, altitude 600–650m, K&M, 28.ii.79 and 26.iv.79 GoogleMaps   .

Diagnosis. Cephalon frontal lamina cleft; vertex with row of 4 lobes, not higher than pereonal lobes, middle two higher than lateral two. Pereon tergite 1–7 each with pair of broad laterally flattened lobes, lateral length of each near height, tergite 1 with one additional anterior transverse ridge-like lobe. Pleonites 3–4 dorsal surface with midline longitudinal tubercle, pleonite 3 tubercle larger than pleonite 4 tubercle. Pleotelson sides slightly constricted. Uropod protopod length 1.6 width; endopod 2.0 exopod length.

Description. Colour uniform brown in alcohol. Original photos show darker uniform brown. Body ( Fig. 4A–C,E) convex with horizontal epimera. Cuticular pits and scales scattered on entire dorsal surface and frons. Cephalon ( Fig. 4E) frontal lamina cleft, raised above vertex; vertex narrow with row of 4 lobes, not higher than pereonal lobes, middle two higher than lateral two, ridge above eyes; eyes small with approximately 10 ocelli. Pereon ( Fig. 4A–D) tergite 1–7 dorsal ornamentation consisting of pair of broad laterally flattened lobes on each tergite increasing in size towards posterior, rest of each tergite with low scattered tubercles, tergite 1 with one additional anterior transverse ridge-like lobe, epimera without tubercles. Epimera 1 narrowly rounded anteriorly, lateral margin simple, posterior margin broadly rounded, dorsal surface concave, ventral surface with longitudinal ridge close to tergite junction extending from anterior margin, ending in tooth-like endolobe anterior to posterior margin; epimera 2 anterior and posterior margins rectangular, anterior margin extending in ventral tooth-like endolobe close to tergite junction; epimera 3–7 anterior margins rectangular, posterior margins grading between rectangular to increasingly rounded, endolobes absent; tergites 1–7 posterior margins slightly curved, tergite 1 length 0.2 pereon length. Pleon ( Fig. 4D) pleura 3–5 truncated, endolobes absent; pleonites 1–5 posterior margins straight; pleonites 3–4 dorsal surface with midline longitudinal tubercle, pleonite 3 tubercle larger than pleonite 4 tubercle. Pleotelson ( Fig. 4F,G) sides slightly constricted, distal part narrower than proximal, length 0.75 proximal width; posterior margin slightly rounded; two rounded tubercles near anterior margin, two ridge-like tubercles near posterior margin. Antenna ( Fig. 4E) short, thick, reaching no further than epimera 1 posterior margin; flagellum length 0.75 article 5 length, flagellar article 2 length 2.0 article 1 length; all segments setose. Mandibles ( Fig. 6A–E). Right mandible lacinia mobilis basal setose lobe with group of long fine simple setae; left mandible with longer and more simple setae, robust penicils not present. Maxilliped ( Fig. 6L–K) basis rectangular. Penes broadly lanceolate; proximal bilobed lamellar process subtriangular, small, length 0.25 penes length. Male pleopod ( Fig. 5A,B) 1 exopod rounded triangular, pseudotrachea along proximal lateral margin, width 0.45 exopod width, length 0.5 exopod length; exopod length 0.4 endopod length. Pleopod 2 exopod proximal wide portion length 0.25 exopod length, length 2.0 exopod width, pseudotrachea along proximal lateral margin, width 0.6 exopod width, length 0.2 exopod length; one lateral long, thick two-segmented seta; endopod proximal article length 0.2 endopod length; exopod length 0.7 endopod length. Uropod ( Fig. 4F,G) protopod subtriangular, apex rounded, length 1.6 width; length (along inner margin of dorsally visible portion) 1.5 width (at point of exopod insertion); exopod visible ventrally through gap between pleotelson and distal part of protopod, apical setae reach posterior margin of protopod; endopod 2.0 exopod length.

Etymology. Polyvelota means “provided with many sails”, referring to the broad laterally flattened, dorsal ornamentation of this species.

Remarks. Stigmops polyvelota   is distinguished from the other species of Stigmops   by the shape and size of the dorsal and pereonites 1–2; A, dorsal view; B, ventral view; C, pleon and pereonites 6–7, dorsal view; D, pleotelson and uropods, ventral view. E–L, paralectotype Ƌ (BMNH 1933.1.25.851–870); E, tip of left mandible, ventral view; F,

pereopod 1, lateral view; G, pereopod 7, lateral view; H, pleopod 1, ventral view, and tip, dorsal view; I, pleopod 2,

and exopod tip, ventral view; J–L, pleopods 3–5, ventral view. Scale bars = 1 mm.

lobes, especially the high cephalic lobes and the stegosaurlike pereonal lobes. This species was rarely encountered in the surveys, suggesting its general rarity in nature.