Xanthonomus thayerae, Shavrin, 2024

Shavrin, Alexey V., 2024, Twenty-one new species of Omaliini from the Papuan Region (Coleoptera: Staphylinidae: Omaliinae), with diagnostic and faunistic notes on some species of the genus Paraphloeostiba Steel, 1960, Zootaxa 5424 (3), pp. 251-307 : 305

Xanthonomus thayerae sp. n.

( Figs 143 , 158–165 )

Type material. Holotype ♂ (dissected): ‘ NEW GUINEA | Mt. Michael | 18.VII.1964 ’ <printed>, ‘ R. Hornabrook | BM 1970-232.’ <printed>, ‘ Xanthonomus | prob. | n.sp. | det. M.K. Thayer 198[printed]9’ <handwritten in black>, ‘ HOLOTYPE | Xanthonomus | thayerae sp. n. | Shavrin A. V. des. 2024’ <red, printed> ( BMNH).

Paratype ♀ ( Fig. 143 ): ‘ NEW GUINEA | Okasa 3600ft, | 11.VII.1965, leaf | mould in pine forest’ <printed>, ‘ R. Hornabrook | BM 1970-232.’ <printed>, ‘ PARATYPE | Xanthonomus | thayerae sp. n. | Shavrin A. V. des. 2024’ <red, printed> ( BMNH).

Description. Measurements (n=2): HW: 0.41–0.45; HL: 0.21–0.25; OL: 0.11–0.13; TL: 0.02; AL (holotype): 0.45; PL: 0.31–0.35; PWmax: 0.53–0.60; PWmin: 0.44–0.50; ESL: 0.47–0.49; EW: 0.68–0.71; MTbL (holotype): 0.33; MTrL (holotype): 0.18 (MTrL 1–4: 0.07; MTrL 5: 0.11); AW: 0.70–0.72; AedL: 0.45; BL: 1.61–1.80 (holotype).

Habitus as in Fig. 143 . Body and antennomeres 7–11 dark brown, with slightly paler middle portion of elytra; femora and basal half of tibia reddish brown; mouthparts, antennomeres 1–6, apical half of tibia and tarsi yellowish. Head with very fine and dense, regular and fine punctation except of clypeus; pronotum with very dense indistinct and fine punctation; elytra with fine and very dense punctation, somewhat similar to that in pronotum, more distinct in basal portion; abdomen without distinct punctures.

Head 1.8–1.9 times as broad as long, with very indistinct anteriomedian depressions; anteocellar foveae reaching level of apical third length of eyes; postocular carina absent. Distance between ocelli about as long as distance between ocellus and posterior margin of eye. Antennomere 2 slightly more than twice shorter than basal antennomere, 4–5 twice shorter than 3, 8 slightly shorter and distintly broader than 7, apical antennomere about 1.2 times as long as 10.

Pronotum 1.7 times as broad as long; anterior margin indistinctly and widely concave.

Elytra reaching middle portion of abdominal tergite III, 1.4–1.5 times as long as pronotum.

Metatarsus 1.8 times as long as metatibia.

Male. Femora and tibia moderately wide. Posterior margin of abdominal tergite VIII straight ( Fig. 161 ). Posterior margin of abdominal sternite VIII indistinctly sinuate ( Fig. 162 ). Aedeagus with wide basal portion, gradually narrowed toward moderately narrow median lobe, in preapical portion narrowed toward small rounded apex; parameres very narrow, reaching apex of median lobe, with two long apical and two preapical setae; internal sac long and moderately wide, with two narrow elongate structures in basal portion ( Fig. 159 ). Lateral aspect of the aedeagus as in Fig. 160 .

Female. Femora and tibia narrow. Posterior margin of abdominal tergite VIII ( Fig. 163 ) and sternite VIII ( Fig. 164 ) truncate. Accessory sclerite as in Fig. 165 .

Comparative notes. Based on the general shape and sculpture of the body X. thayerae sp. n. is similar to X. guineensis sp. n., from which can be distinguished by the slightly shorter body, narrower median lobe and distinctly longer parameres.

Distribution. Xanthonomus thayerae sp. n. is known from two localities in central part of Papua New Guinea ( Fig. 158 ).

Etymology. Patronymic, the species is named after my colleague Margaret K. Thayer (Chicago), specialist in Omaliinae .

Bionomics. The paratype was collected in leaf mould in pine forest.

Figures

FIGURE 158. Distribution of Xanthonomus: X. toxopeanus (circle), X. latus (triangle), X. guineensis (squares), X. thayerae (diamonds).

FIGURES 159–165. Xanthonomus thayerae: 159–aedeagus, parameral view (holotype), 160–aedeagus, lateral view (holotype), 161–male abdominal tergite VIII, 162–male abdominal sternite VIII, 163–female abdominal tergite VIII, 164–female abdominal sternite VIII, 165–female accessory sclerite. Scale bar: 0.1 mm.

FIGURES 141–143. Habitus of Omaliini: 141–Paraphloeostiba telnovi (holotype), 142–Xanthonomus guineensis (holotype), 143–X. thayerae (paratype). Scale bars: 1.0 mm.