Rotundicephala Tasaku, Ono & Maruyama, 2023

Tasaku, Yuto, Ono, Hiroki & Maruyama, Munetoshi, 2023, Review of the intertidal rove beetle tribe Liparocephalini Fenyes (Coleoptera, Staphylinidae, Aleocharinae) from Japan, Zootaxa 5383 (3), pp. 251-296 : 271-272

Rotundicephala Tasaku, Ono & Maruyama , gen. n.

[Japanese name: Kuroshio-umi-hanekakushi-zoku]

Type species. Rotundicephala pacifica ( Sawada, 1971) , comb. n.

Diagnosis. This new genus is similar to Diaulota but can be distinguished by a combination of the following characteristics: tarsal formula 3-3-4, head almost circular ( Fig. 1C ), body color usually reddish brown ( Fig. 14 ). Abdomen is more elongate than that of Diaulota . See also the diagnosis of Diaulota .

Description. Body small; reddish brown in ground color, abdominal segments V–VII almost black in most cases, mouthparts and legs slightly paler. Head slightly convex or flattened, almost circular, as long as wide ( Fig. 1C ); eyes small; infraorbital carina present; antennae 11-segmented, segments I–III strongly elongate, segment I longer than II, segment III shorter than II, segments IV–XI moniliform ( Figs. 15G–I ). Labrum semicircular ( Fig. 16A ). Mandibles almost symmetric, with one large tooth present around middle, and right teeth larger than left one ( Fig. 16E ). Prementum without medial seta; ligula unilobed, very short, about 1/3 length of segment I of labial palpus; labial palpus two-segmented, segment I incompletely divided in basal 1/3, segment I very long, and segment II short and thin ( Fig. 16C ). Maxilla slender; lacinia with about 8 spines; maxillary palpus 4-segmented, segment I very short, segment II three times as long as I, segment III longer than II, and segment IV as long as I ( Fig. 16D ). Mentum almost trapeziform, anterior margin deeply emarginated ( Fig. 16B ). Pronotum almost oval. Elytra short. Hind wings reduced. Tarsal formula 3-3-4. Abdomen oblong oval.

Male: tergite VIII with truncate apical margin; sternite VIII cuspidate at apical margin; apical lobe of median lobe unilobed and strongly curved, athetine bridge absent ( Figs. 15A, C & E ); apical lobe of paramere narrow rectangle ( Fig. 2G ).

Female: tergite VIII with truncate apical margin; sternite VIII rounded at apical margin.

Remarks. In a previous study, Sawada (1971) classified R. pacifica comb. n. within Diaulota , noting that there were no fundamental differences except for the tarsal formula from other Diaulota species. However, Yoo & Ahn (2021) suggested that R. koreana comb. n. may not actually belong to Diaulota . This study confirms that three species belonging to Rotundicephala gen. n. share two important morphological characteristics: a rounded head and a tarsal formula of 3-3-4. These two characteristics are not found in Diaulota . While the reduction of tarsi is often observed in Liparocephalini , the exclusive 3-3-4 tarsal formula is a distinctive character state of Rotundicephala gen. n. to distinguish it from Diaulota .

Etymology. The generic name means round head. Gender feminine.

Distribution. Japan: Honshû, Shikoku, Kyûshû; South Korea.

Key to the species of Rotundicephala gen. n.

1. Antennae long, reaching to elytra, collected from gravel beach.................................. R. koreana comb. n.

- Antennae short, not reaching to elytra, collected from rocky shore............................................... 2

2. Head and pronotum slightly convex, antennal segments IV–IX as long as wide......................... R. koheii sp. n.

- Head and pronotum flattened, antennal segments IV–VIII transverse.............................. R. pacifica comb. n.

Figures

FIGURE 1 Definitions of measurements of body parts. A, adult of Diaulota; B, head of Diaulota aokii, dorsal view; C, head of Rotundicephala koheii sp. n., dorsal view.

FIGURE 2 Aedeagal parameres of Liparocephalus, Diaulota and Rotundicephala gen. n. spp. A & D, parameres of aedeagus (A, L. tokunagai; D, D. aokii); B, C, E, F & G, apical lobe of parameres (B, L. litoralis; C, L. tokunagai; E, D. aokii; F, D. uenoi; G, R. koheii sp. n.). Scale bars: 0.1 mm.

FIGURE 14 Habitus of Rotundicephala gen. n. spp. A, R. pacifica comb. n.; B, ditto, female; C, R. koreana comb. n.; D, R. koheii sp. n., male (holotype). Scale bar: 1.0 mm.

FIGURE 15 Genitalia and antenna of Rotundicephala gen n. A, B & G, R. pacifica comb. n. (A, median lobe of aedeagus; B, spermatheca; G, right antenna); C, D & H, R. koreana comb. n. (C, median lobe of aedeagus; D, spermatheca; H, right antenna); E, F & I, R. koheii sp. n. (E, median lobe of aedeagus; F, spermatheca; I, right antenna). Scale bars: 0.1 mm.

FIGURE 16 Mouth parts of Rotundicephala koheii sp. n.A, labrum (right side, dorsal view; left side, ventral view (epipharynx)); B, mentum; C, labium; D, maxilla; E, right mandible. Scale bar: 0.1 mm.