Pseudothinusa Tasaku & Maruyama, 2023

Tasaku, Yuto & Maruyama, Munetoshi, 2023, Pseudothinusa sunahama, a new genus and species of the tribe Athetini (Coleoptera, Staphylinidae, Aleocharinae) from sandy beaches in Japan, Zootaxa 5244 (1), pp. 33-40 : 34-37

Pseudothinusa Tasaku & Maruyama , gen. nov.

(Figs. 1–18)

Type species. Pseudothinusa sunahama .

Etymology. Meaning “false Thinusa ” because of its morphological similarity to the genus Thinusa .

Diagnosis. Pseudothinusa may be distinguished from other athetine genera by combination of following character states: front and middle tibiae with spines; integument with strong microsculpture; mentum with short v-seta; mandible with slightly sharp apex; complete infraorbital carina.

Among the coastal athetine species in East Asia, Pseudothinusa gen. nov. is the most similar to Adota Casey, 1910 in general appearance. However, Pseudothinusa differs from Adota in having a complete infraorbital carina and spines on the front and middle tibiae. Pseudothinusa also differs from Psammostiba Yosii & Sawada, 1976 , another seashore-dwelling athetine genus, in having a smaller body size (2.0–2.8), tarsi with single empodial seta and the presence of spines on the front and middle tibiae. Compared to the genus Eubadura Sawada, 1990 and the coastal species of the genus Atheta , Pseudothinusa gen. nov. is clearly distinguishable by its slenderer body and the presence of spines on the front and middle tibiae. See also Discussion for comparisons with coastal species in other regions.

Description. Body (Fig. 1) flat and subparallel; Microsculpture of head, pronotum, and abdominal segments strong (Figs. 1–2).

Head. Head approximately circular. Eyes with microsetae between facets (Fig. 2). Cervical carina and infraorbital carina complete. Antennae 11-segmented, moniliform.

Mouthparts. Labrum (Fig. 4) strongly transverse (width/length ratio 1.8), with 8 pairs of macrosetae. Epipharynx (Fig. 5) with normally developed sensillum a. Mandibles (Figs. 6–7) with slightly sharp apex, asymmetric; left mandible (Fig. 6) generalised, without teeth; Right mandible (Fig. 7) with a medium tooth at middle of inner margin, weakly serrate between tooth and apex. Labium as in Fig. 8. Prementum (Fig. 8) with 2 real pores and 1 setal pore latero-mesally; lateral lobe of apodeme long. Ligula (Fig. 8) bilobed, with each lobe rounded and covered with minute pores apically; apical setae absent; lateral margin weakly sclerotized. Labial palpus (Fig. 8) with segment I long and twice as long as II; segment III as long as I. Maxilla as in Fig. 9. Cardo as in Fig. 9. Stipes (Fig. 9) small, triangular, with 3 setae around base. Palpifer (Fig. 9) triangular in lateral view, with one large seta near apex, two small setae at middle and apex. Lacinia (Fig. 9) generalized; inner margin with a row of 8 spines in apical 1/3, dense setae in basal 2/3 and two setae in basal 1/3. Galea (Fig. 9) slender, about 3 times as long as wide, curved at middle, densely pubscent apically. Maxillary pulpus as in Fig. 9; segment I short; segment II with about 10 setae; segment III largest, 1.5 times longer than 2nd, with about 30 setae; IV segment without setae. Mentum (Fig. 10) trapeziform; v-seta short; surface moderately covered with pseudopores except for lateral area.

Thorax. Pronotum (Fig. 1) slightly transverse, with thick setae toward lateral side. Prosternum transverse. Scutellum generalized, covered with setae. Hypomera visible laterally. Mesoventral process pointed at apex. Metaventral process, pointed at apex, shorter than mesoventral process. Mesocoxal cavity unmargined, separated by isthmus. Hind wing present.

Legs. Tarsal formula 4-5-5; front and middle tibiae with spines (Fig. 3). Empodium simple; empodial seta as long as long as claw.

Abdomen. Abdomen (Fig. 1) parallel side; abdominal chaetotaxy 02 type (sensu Yosii & Sawada, 1976).

Male characteristics. Tergite VIII (Fig. 14) posterior margin irregularly dentate; sternite VIII (Fig. 15) simple. Aedeagus: median lobe (Figs. 11–12) entirely oval, apical process broad. Apical lobe of paramere (Fig. 13) with 4 setae; a-seta as long as b-seta; c- and d-setae very short.

Female characteristics. Tergite VIII (Fig. 16) and sternite VIII (Fig. 17) simple, posterior margin not dentate. Spermatheca (Fig. 18) with basal part of stem twice curved around base.

Distribution. Japan: Hokkaidô, Honshû, Shikoku, Kyûshû (Nokono-shima)