Notopais Hodgson, 1910

Merrin, Kelly L., 2004, Review of the deep­water asellote genus Notopais Hodgson, 1910 (Crustacea: Isopoda: Munnopsididae) with description of three new species from the south­western Pacific, Zootaxa 513, pp. 1-27 : 3-5

Notopais Hodgson, 1910

Notopais Hodgson, 1910: 69 .

Type species Notopais spicatus Hodgson, 1910 , by monotypy.

Diagnosis: Cephalon frons narrow, allowing for almost horizontal position of maxillipeds in situ in lateral view. Pereonites 1–4 anterior margins usually with spines, if not, margins with robust setae; all spines tipped with robust (pedestal) setae, making spines look more pronounced. Antenna 2 article 1 distolateral angle with horn­like prominent spine and terminal robust seta. Mandible palp absent; incisor process large, rounded, without defined cusps; lacinia mobilis reduced or absent. Pereopods 5 and 6 carpus and propodus flat, expanded, margins with plumose setae. Pereopods 7 ambulatory, robust, retains plumose setae similar to pereopods 5 and 6. Uropods biramous.

Description: Body compact, cuticle brittle; cephalon trapezoid, broad, wider posteriorly, dorsal face domed, ventrally, cephalon flattened, frons narrow allowing maxillipeds to appear almost horizontal in lateral view. Pereonites 2–4 anterolateral margins usually with spines, anterior margins usually with spines, if not, margins with robust setae; all spines tipped with robust (pedestal) setae, making spines look more pronounced. Antenna 2 articles 1–4 short, combined length less than half of length of article 5; article 1 distolateral angle with prominent spine, horn­like, and terminal robust seta; article 6 more elongate than 5. Mandible massive, calcareous; palp absent; incisor process large, rounded, without defined cusps; lacinia mobilis reduced or absent. Pereopods 5 and 6 carpus expanded, discoidal, flat; propodus flat, expanded; superior margin of ischium and both margins of carpus and propodus with row of evenly­spaced long plumose setae. Pereopod 7 ambulatory, but more robust and retaining long, plumose setae similar to that of pereopods 5 and 6. Pleon triangular in dorsal view, with domed medial keel. Operculum vaulted, with prominent medial keel. Uropods biramous, small, flat.

Remarks: Notopais can be distinguished by: the flattened appearance of its mouthparts in situ, pereonites 1–4 anterior margins most commonly with spines or otherwise with robust setae; all spines tipped with robust (pedestal) setae; antenna 2 article 1 with produced anterolateral angle with a distal robust seta; pereopods 5, 6 and 7 with superior margin of ischium and both margins of the carpus and propodus with row of evenly spaced long, plumose setae; and uropods biramous, small and flat.

On studying Sars’ material of Echinozone coronata ( Sars, 1870) the type species for Echinozone genus, it can be found that Notopais differs from this genus in cephalon and body shape, the presence of pedestal setae and with the distinct shape of antenna 2 article 1. In Notopais the frons is narrower compared with Echinozone , allowing the frontal arch to meet up with the maxillipeds at a wider angle, giving them a more horizontal appearance. The more acute angle between the frontal arch and maxillipeds seen in Echinozone gives it a much more triangular appearance, especially in lateral view. This structure adds more emphasis on the curvature of the animal and its body is more arched than in Notopais . Notopais has pedestal setae tipping all of its spines, similar to that found in Bathybadistes and these are not present in Echinozone . Although many Ilyarachninae (including Echinozone ) have a robust seta and/or a spine on the anterolateral angle of antenna 2 article 1, the shape of this in Notopais is distinct and exclusive to this genus. Its shape is akin to a bull’s horn and is always tipped with a robust seta making it more pronounced.

This genus now contains: Notopais beddardi n. sp., N. zealandica n. sp., N. minya n. sp., N. magnifica ( Vanhöffen, 1914) comb. nov., N. quadrispinosa ( Beddard, 1886) comb. nov., N. spicata Hodgson, 1910 (type species) and N. spinosa ( Hodgson, 1902) comb. nov. The genus appears to be restricted to the Southern Hemisphere, from Antarctic waters to the south­east continental slope of Australia, at depths from 36 to 1640 metres.

Key to the species of Notopais

1. Anterior margin of pereonite 5 with large, distinct spines ............................................ 2

— Anterior margin of pereonite 5 either smooth, with robust setae or small spines only. 3

2. Cephalon with pair of short dorsal spines; pereonite 4 with anterior facing spines set back from anterior margin, most marginal spines on pereonites with body margins; anterolateral margins of pereonites 5 and 6 pointing towards cephalon ........................ .............................................................................................................. N. quadrispinosa

— Cephalon with pair of large, distinct dorsal spines; pereonite 4 with anterior facing spines on anterior margin; all marginal spines on pereonites are well defined and acutely angled; anterolateral margins of pereonites 5 and 6 rounded ............. N. spicata

3. Cephalon with dorsal spines; pereonites 1–4 with large spines; anterior margin of pereonite 5 normal, continuous, without overhang.............................................................. 4

— Cephalon with no dorsal spines; pereonites 1–4 with robust setae only, large spines absent; pereonite 5 with anterior margin overhanging pereonite 4 .. N. zealandica n. sp.

4 Cephalon with 4 dorsal spines (not including, if present, any on anterolateral margins) ....................................................................................................................................... 5

— Cephalon with 2 dorsal spines only, no small spines on anterolateral margins; no submarginal lateral spines on pereonite 4; anterior margin of pereonite 5 with stiff robust

setae; antenna 2, articles 1 and 2 distosuperior margin with row of 4 robust setae ........ ............................................................................................................. N. beddardi n. sp.

5. Pereonites 6–7 dorsal surface with no spines; cephalon with no spines on anterolateral margins.........................................................................................................................6

— Pereonites 6–7 dorsal surface both with pair of small spines; cephalon anterolateral margins each with single small spine, another pair of spines are set well back from margin but are not on central dome; pereonite 5 anterior margin with 4 small spines .. ........................................................................................................................ N.spinosa

6. Cephalon with 4 spines, which are small enough to be regarded as tubercles; pereonites 2–3 anterior margin with 6 spines; pereonite 5 anterior margin smooth; antenna 2 article 1 only article with distolateral angle with defined spine and terminal robust seta ................................................................................................................. N. minya n. sp.

— Cephalon with 4 large, distinct spines, the inner pair larger than outer pair; pereonites 1–4 anterior margins with continuous row of spines (when mature adult); pereonite 5 dorsalsurfacewithpairofroundeddomes,oneeachsideofcentre, anteriormarginsmooth N. magnifica