Stephenseniellus serraticornis, Just, Jean & Wilson, George D. F., 2006

Just, Jean & Wilson, George D. F., 2006, Revision of Southern Hemisphere Austronanus Hodgson, 1910, with two new genera and five new species of Paramunnidae (Crustacea: Isopoda: Asellota), Zootaxa 1111, pp. 21-58 : 54-56

Stephenseniellus serraticornis sp. nov.

( Fig. 19 )

Paramunna ( serrata (Richardson) ?).– Stephensen, 1927: 359, fig. 25.

Etymology. The species name is derived from the Latin serratus (with teeth) and cornu (horn, traditionally used for the antennae) alluding to the row of strong denticles on the lateral margin of article 3 of the antennae.

Remarks on type material. The holotype lacks all pereopods. Stephensen (1927, fig. 25P1) illustrated pereopod I; we have redrawn his illustration in our Fig. 19 p1.

Material examined

Holotype. ɗ, 1.9 mm, Carnley Harbour, Auckland Island, New Zealand, on the shore under stones at low tide, 29 November 1914, ZMUC­CRU­4920.

Description. Body widest in male at pereonite 2 or 3. Head length 0.70 width; length posterior to eyestalks 1.3 anterior length. Frontal margin lobe length 0.30 head length; apex broadly rounded in dorsal view. Eyestalks lateral apex broadly rounded, shaft curving posteriorly, long axis angling forward 35° in male.

Pereonite lateral margin 1–4 linear, 5–7 angular, not projecting over coxae, with posterior concavity. Pereonite 5 in dorsal view distinctly narrower than pereonites 4 and 6. Pereonite 5–7 lateral margins with robust setae.

Pleon length 0.84 width in male. Pleonite 1 width 1.1 distance between uropods, length 0.3 width. Pleotelson proximal margin length subequal to lateral margin length; laterally produced, inflection near middle of lateral margin; proximal margin in dorsal view forming 45° angle with medial axis of pleon; lateral margins denticulate, denticles largest at rounded corners, low denticles more posteriorly, with 4 denticles per side, several additional fine denticles more posteriorly; posterior margin in male forming 135° angle, set apart from lateral margins by slight concavity at level of uropods.

Antennula with 5 articles; articles 1and 2 combined shorter than eyestalk; article 1 longer and broader than 2, inflated; article 2 with distoventral projection, distal articles inserting dorsally; distal article 5 shorter than articles 3 and 4 combined.

Antenna article 2 lateral margin with 4 denticles, 2 larger plus 2 smaller; article 3 in ventral view inflated midlength, lateral margin curved, medial margin straight, width 0.67 length, lateral margin with 5 coarse denticles; article 5 only slightly longer than article 4; flagellum with 7 articles, proximal article 1.4 length of second article.

Pereopod I coxa with lateral lobe visible in dorsal view; basis anterior margin smooth, length 1.85 width; carpus distal width 1.0 posterior margin length, posterior margin with 2 denticles proximal to robust setae, one denticle between robust setae, one denticle distal to robust setae (broad flange­like); propodus distally broad and tapering steeply to insertion of dactylus, with 2 robust setae. Pereopods V–VII coxae lateral margins angular and projecting, with posterior concavity, with single apical robust seta.

Male pleopods I lateral lobes distinctly projecting from midlateral margin, width 0.3 distance to midline; distal projection length 0.22 pleopod total length, forming approximately 100° angle, with pointed apices.

Uropods on lateral margin of pleotelson.

Size. Largest male 1.90 mm.

Distribution. Auckland Island, New Zealand, intertidal.

Remarks. See Remarks above under Stephenseniellus palliolatipes sp. nov. for comparison with that species.

Figures

FIGURE 19. Stephenseniellus serraticornis, sp. nov. Holotype, male. a, antenna; au, antennula; cv, ventral view of head; cx 1, coxa I; md, mandible; pe 5 ­ 7, pereonites 5 ­ 7 with coxae; p 1, pereopod I (redrawn from Stephensen, 1927: 360, fig. 25), pl 1 ­ 2, pleopods I, II; pt, pleotelson; up, uropod; vv, ventral view. Habitus scale bar: 0.5 mm.