Austramastodus, Hernando, 2023

Hernando, Carles, 2023, A new flightless genus of Thaumastodinae from Australia (Coleoptera: Limnichidae), Zootaxa 5315 (6), pp. 559-566 : 560-561

Austramastodus gen. nov.

Type species. Austramastodus apterus sp. nov.

Diagnosis. Austramastodus gen. nov. differs from the other members of Thaumastodinae with the tarsal formula 4–4–4, in the narrow elongate body shape, transverse head with the frons not projecting forward, widely separated eyes (space between them being larger than an eye diameter) and the weakly sinuate pronotum.

Description. Length: 2.16–2.50 mm (head included). Integument unicolored dark brown. Body form ( Figs. 1–3 ) elongate-oval, dorsal surface covered with short and recumbent silvery pubescence and spots of golden pubescence.

Head: Strongly hypognathous ( Figs. 1–4–5 ), transverse; frons broad, not projecting forward; eyes large, subcircular and slightly convex ( Figs. 4–5 ); frontoclypeal suture straight, shallow and inconspicuous; antennal insertion exposed, laterally contiguous the frontoclypeal suture ( Fig. 5 ); antennal groove present and shallow, where only the first six antennomeres fit ( Fig. 5 ). Antenna 11-segmented, short and stout, with 4-segmented and slightly asymmetrical antennal club; scape and pedicel enlarged, antennomere 3 stout, antennomeres 4–7 narrow, antennomeres 8–10 dilated and gradually shortened. Labrum subquadrate ( Fig. 5 ). Maxillary palps 4-segmented, last palpomere enlarged and apically acuminate. Labial palps 3-segmented.

Thorax: Pronotum ( Figs. 1–4 ) transverse, about twice as wide as long; lateral margins practically straight, slightly narrowing medially, posterior margin slightly sinuate ( Fig. 4 ); anterior angles broadly acute, posterior angles rounded; disc with coarse and somewhat rough punctation, covered with dense and short golden and silvery setae ( Fig. 2 ). Hypomeron broad and slightly depressed, without suture or carina, covered with short silvery setae. Prosternum: area before procoxae about 0.7 times as long as coxal cavities; prosternal process slightly longer than wide, flat and finely bordered laterally, apically bluntly pointed. Scutellum small and triangular. Elytra very long, twice as long as wide ( Fig. 1 ); lateral margins finely beaded along their entire length; apical interlocking device connecting elytra and last sternite, well developed; surface of disc shiny, densely and finely punctate, covered with recumbent, generally silvery setae, but in some areas with golden spots; epipleuron broad at base and slightly impressed to receive femoral tips, extending to apical interlocking device. Hind wings absent. Mesoventrite short and transverse, with large anterior depression to receive prosternal process. Metaventrite projecting posteriorly, covering the metacoxa. Mesocoxae slightly transverse, trochantins exposed. Metacoxae strongly transverse and oblique, subcontiguous; metacoxal plates ( Fig. 2 ) large and strongly expanded laterally, posterior margins with two pointed projections, partly covering metatrochantins ( Fig. 2 ). Forelegs relatively short and stout, with a few apical spines; tibia clearly shorter than femur. Middle legs relatively short and stout, with a few apical spines; tibia as long as femur. Hind legs very long, with a longitudinal row of strong spurs; tibia much longer than femur. All legs sexually dimorphic, especially protarsus ( Fig. 5 ) and claws (see below). Tarsal formula 4–4–4.

Abdomen: ( Fig. 2 ) with five ventrites, covered with short recumbent setae, finely punctate (not very dense and uniform), and covered by a polygonal squamiform reticulation; intercoxal process of the first abdominal ventrite very small; first three ventrites connate; ventrite 1 long; ventrites 2–4 subequal in length; lateral margin of ventrite 5 with a pair of subapical notches ( Figs. 6–7 ) (being part of the elytral-abdominal interlocking device); setation and apex of ventrite 5 sexually dimorphic (see below).

Aedeagus. Articulated and strongly arched in lateral view ( Fig. 9 ), with the base longer than the parameres ( Figs. 8–9 ); median lobe with the apex strongly curved inwards, falciform in shape ( Figs. 8–9 ).

Female genitalia. Ovopositor in ventral view as in Fig. 12 ; gonocoxal struts very long, ten times the length of gonocoxites; gonocoxites strongly acuminate ( Figs. 12–14 ) and articulate at apex of the gonocoxal struts. Spiculum ventrale with a long manubrium, distal part with two long lateral expansions ( Figs. 13–15 ).

Differential diagnosis. Austramastodus gen. nov. can be clearly distinguished from the other genera of Thaumastodinae ( Acontosceles Champion, 1924 , Pseudeucinetus , Mexico and Martinius Spilman, 1959 ) by the widely separated eyes, which are in lateral position and with the space between them larger than the diameter of an eye (eyes close together and in a more frontal position in the other four genera and with the space between the eyes always narrower than the maximum length of an eye). Additional distinguishing characters: tarsal formula 4–4–4 (4– 5– 5 in Acontosceles ); 11-segmented antennae (7-segmented in Martinius ); lateral margin of elytra smooth (serrate in Martinius and Mexico ); presence of antennal groove (lacking in Martinius ); remarkable sexual dimorphism in the protarsus (lacking in Acontosceles , Martinius and Mexico ); eyes large and subcircular (narrow and elongated in Martinius , Mexico and Pseudeucinetus ).

Within the subfamily, Austramastodus gen. nov., seems to be close to Pseudeucinetus , from which it can be distinguished (apart from the position of the eyes) by the following characters: body form elongate-oval (vs. fusiform in Pseudeucinetus ); head transverse and regularly curved (vs. projecting forward and pointed); posterior margin of the pronotum weakly sinuate (vs. strongly sinuate); male with mesotarsal and metatarsal claws asymmetrical (vs. symmetrical); parameres and median lobe shorter than the phallobase, strongly curved apically (vs. equal length or longer, always straight); lamina of the genital segment extending beyond insertion of the parameres (vs. lamina not extending, parameres inserted at the apex of the lamina); gonocoxites separate (vs. convergent and strongly acuminate).

Figures

FIGURES 1–7. Austramastodus apterus sp. nov. 1. Male habitus, dorsal view. 2. Male habitus, ventral view. 3. Male habitus, lateral view. 4. Head and pronotum, fronto-dorsal view. 5. Head, fronto-lateral view and male fore tarsi. 6. Male last abdominal sternite. 7. Female last abdominal sternite. The arrow points to the only two large lateral spiniform setae on the female.

FIGURES 8–15. Austramastodus apterus sp. nov. 8. Aedeagus, ventral view. 9. Aedeagus, lateral view. 10. Ninth male genital segment, ventral view. 11. Male sternite VIII. 12. Gonocoxites and gonocoxal struts, ventral view. 13. Spiculum ventral. 14. gonocoxites 15. Spiculum ventral, distal plaque.