Marmenuera, Dean & Forteath & Osborn, 2008

Dean, J. C., Forteath, G. N. R. & Osborn, A. W., 2008, Marmenuera, a new genus of leptophlebiid mayfly (Insecta: Ephemeroptera) endemic to Tasmania., Memoirs of Museum Victoria 65, pp. 43-50 : 43-44

Genus Marmenuera gen. nov.

Diagnostic features. Imago. Forewing (figs 1, 3, 17, 19): membrane hyaline, cells in apical third of wing translucent white; veins brown, many crossveins suffused with dark brown pigmentation; length-width ratio of forewing slightly less to slightly greater than 3.0; four to seven costal crossveins basal to the bulla, 11–19 distal to the bulla; MA forked at 0.40–0.43 wing length; MP 2 attached by crossvein to MP 1 at 0.18–0.20 wing length; base of ICu 1 linked to both CuA and CuP by a crossvein; ICu 1 and ICu 2 strongly diverging as wing margin approached. Hindwing (figs 2, 4, 18, 20): 0.22–0.26 length of forewing; length/width ratio 1.6–1.9; costal margin with shallow concavity at about midlength, costal space broader both basal and distal to the concavity; vein Sc joining costal margin at 0.8–0.85 wing length; 7–13 costal crossveins and 6–11 subcostal crossveins. Legs: yellow or medium brown, all femora with two strongly developed dark brown bands, one at midlength and the other near the apex; tarsal claws similar, each claw with an apical hook and opposing ventral flange (fig. 9); forelegs of male with ratios of segment lengths 0.81–0.86, 1.00, 0.05–0.07, 0.34–0.35, 0.34–0.38, 0.26–0.30, 0.11–0.23. Male genitalia (figs 7, 8, 24, 25): claspers three-segmented, basal segment narrowing abruptly at about midlength; penes lobes fused in basal half, widely separated apically; each lobe relatively broad and approximately parallel-sided, with three moderate sized ventral spines close to inner margin and slightly posterior to where the lobes separate (fig. 8). Female sternum nine with apical margin deeply excised ( Fig. 10 ). S ubimago. Wings pale fawn/white, brown blotches and/or suffusions similar in distribution and intensity to corresponding imago. Mature nymph. Head prognathous; antennae at least half length of body. Mouthparts: clypeus with lateral margins sub-parallel; labrum (figs 12, 27) slightly wider than clypeus, width 1.7–1.9 times length along median line, anterior margin with shallow to moderate mesal concavity, frontal setae arranged as single row, sub-apical setae arranged in a single row set back from anterior margin at about 0.9x labrum length; mandibles with outer margin somewhat angular at midlength, gently curved basally and distally, a tuft of long setae around midlength and a sparser series of long setae basal to the tuft, incisors slender, prostheca strongly developed; maxillae quadrate, subapical row of 30–35 pectinate setae, palp moderately short, three segmented, terminal segment almost as long as middle segment, middle segment bearing simple setae only; labium with glossae elongate, turned under ventrally, palp three-segmented, terminal segment almost as long as middle segment and with series of small spine-like setae along inner margin, submentum with fringe of long setae along lateral margins. Legs banded; femora moderately broad (figs 13, 28); tarsal claws smooth, without ventral teeth (figs 14, 29). Abdominal segments without setae on lateral margins, postero-lateral spines on segments 7–9; posterior margins of abdominal terga with series of long, robust spines interspersed with minute spines (fig. 15). Gills present on abdominal segments 1–7; each gill lanceolate, lateral tracheae strongly developed (fig. 16). Caudal filaments about 1½ times length of body; each segment with apical whorl of both stout spine-like setae and fine hair-like setae, spine-like setae predominating near base of each filament but becoming shorter towards midlength where the hair-like setae predominate.

Type species. Marmenuera tillyardi sp.nov.

Etymology. The generic name is derived from “mar.me.nuer”, the western Tasmanian aboriginal word for “country” or “tribal territory” ( Plomley 1976, p.191), and pertains to the endemicity of the genus to Tasmania.

Remarks. The genus Marmenuera can be distinguished from all other leptophlebiid genera by the following combination of characters. Imago: (1) basal half of forewing with costal crossveins heavily suffused with dark brown, often with brown pigmentation more extensive; (2) forewing with ICu 1 attached to CuA and CuP by crossveins; (3) ICu 1 and ICu 2 strongly diverging as wing margin approached; (4) hindwing with shallow concavity at about midlength, and Sc joining wing margin at 0.8–0.85 wing length; (5) tarsal claws similar; (6) male genitalia with penes fused in basal half and widely separated apically, with three moderate-sized ventral spines situated slightly posterior to where the lobes separate; (7) female sternum nine with apical margin deeply excised.

Nymph: (1) labrum slightly wider than clypeus; (2) width of labrum 1.7–1.9 times length along median line; (3) labium with glossae elongate and turned under ventrally; (4) terminal segment of labial palp with series of small spine-like setae along inner margin; (5) submentum with fringe of long setae along lateral margins; (6) tarsal claws smooth; (7) gills lanceolate, moderately broad; (8) posterior margins of abdominal terga with row of stout spines interspersed with small spines.

Marmenuera does not fit into any of the leptophlebiid lineages defined by Pescador and Peters (1980), and Towns and Peters (1980), and its closest relatives are probably here in Australia. The genus appears most closely related to Loamaggalangta Dean, Forteath and Osborn and Bibulmena Dean. The three genera share many characters, including attachment of the base of ICu 1 to the CuA–CuP crossvein in the forewing, similar tarsal claws in the imago, a deeply excised sternum nine in the female, similarities in the nymphal mouthparts (in particular the elongate and underturned glossae, the fringe of setae on the lateral margins of the submentum and the small spine-like setae along the inner margin of segment 3 of the labial palps) and smooth tarsal claws in the nymph. Christidis (2005) placed Bibulmena and Loamaggalangta at the base of a large clade containing many of the Australian leptophlebiid genera, but found no support for the grouping of these two genera into a monophyletic clade. The character states listed above are perhaps primitive and not synapomorphies.

Figures

Figures 5–10. Marmenuera tillyardi. Male imago: 5, abdomen, dorsal; 6, abdomen, ventral; 7, penes, dorsal; 8, penes, ventral, slide preparation; 9, foretarsal claw. Female imago: 10, sternum nine.