Cretobrachygluta, Yin & Kurbatov & Cuccodoro & Cai, 2019

Yin, Zi-Wei, Kurbatov, Sergey A., Cuccodoro, Giulio & Cai, Chen-Yang, 2019, Cretobrachygluta gen. nov., the first and oldest Brachyglutini in mid-Cretaceous amber from Myanmar (Coleoptera: Staphylinidae: Pselaphinae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 59 (1), pp. 101-106 : 102-103

† Cretobrachygluta gen. nov.

( Figs 1–2 )

Type species. † Cretobrachygluta laurasiensis sp. nov., here designated.

Diagnosis. Head with small, nude vertexal foveae, lacking sulcus connecting foveae; antennae with club formed by apical three antennomeres; gular region with broad median ridge. Pronotum with small, nude median and lateral antebasal foveae. Each elytron with four basal foveae; subhumeral foveae and marginal striae present; discal striae absent. Metacoxae contiguous, moderately projecting posteriorly; tarsomere 2 distinctly shorter than tarsomere 3; tarsi each with single pretarsal claw. Abdomen with tergite 1 (IV) much longer than 2 (V); tergites 1–4 (IV–VII) with broad paratergites; tergite 1 (IV) with two basolateral foveae, lacking mediobasal fovea; sternite 1 (III) as long as 2 (IV) along midline.

Description. Body length slightly over 1.8 mm; habitus ( Fig. 1 ) strongly convex dorso-ventrally, in dorsal view strongly broadened posterior to pronotum.

Head ( Fig. 2B ) roundly quadrate, slightly wider than pronotum; vertex raised, with pair of small and nude vertexal foveae ( Fig. 2A ; vf); frons shallowly and broadly impressed, impression flanked laterally by widely separated antennal tubercles, and demarcated anteriorly by broad frontal-clypeal ridge; ocular-mandibular carinae ( Fig. 2D ; omc) distinct; gular region broadly impressed at middle, two close but clearly separated foveae ( Fig. 2C ; gf) in impression; broad, longitudinally oval median gular ridge present anterior to foveae and extending to mouthparts, demarcated laterally by sulci. Antennae ( Fig. 2A ) eleven-segmented; club well-developed, formed by apical three antennomeres, with sub-oval and basally truncate antennomeres 11 ( Fig. 2A; a 11) much wider than preceding antennomeres. Maxillary palpi four-segmented; palpomere 1 minute, elongate, palpomere 2 pedunculate in basal half, strongly broadening toward apex, palpomere 3 subtriangular, approximately as wide and half as long as palpomere 4, palpomere 4 ( Fig. 2B ; mp4) largest, sub-oval, with elongate apical palpal cone.

Pronotum ( Fig. 2B ) slightly elongate, widest at apical third; lateral margins rounded, sides convergent toward apex at apical two-fifths and narrowing toward base at basal third; disc with nude median ( Fig. 2B ; maf) and lateral antebasal ( Fig. 2B ; laf) foveae subequal in size, lacking additional carinae, sulci or tubercles; paranotal carinae either short, or lacking; lateral procoxal foveae present, moderately separated.

Elytra ( Fig. 2B ) slightly wider than long, widest point posterior to middle; each elytron with four small but distinct basal foveae ( Fig. 2B ; bef); sutural striae ( Fig. 2B ; ss) complete; discal striae absent; subhumeral foveae ( Figs 2B, 2D ; shef) present; short marginal striae ( Figs 2B, 2D ; ms) extending from subhumeral foveae to basal third of elytral length; posterolateral clefts ( Fig. 2B ; plc) broad and shallow. Hind wings fully developed.

Thorax with narrowly separated median mesoventral foveae ( Fig. 2C ; mmsf); lateral mesoventral foveae ( Fig. 2D ; lmsf) simple; lateral mesocoxal foveae ( Fig. 2C ; lmcf) and lateral metaventral foveae ( Fig. 2C ; lmtf) present; lateral sutures separating meso- and metaventrite well-marked, fully developed; posterior margin of metaventrite with narrow split at middle.

Abdomen ( Figs 2 A–C) dorsoventrally flattened, with generally rounded lateral margins; segments telescoping. Five tergites (IV–VIII) ( Figs 2A, 2B ; tIV–VIII) visible, with broad paratergites on segments 1–4 (IV–VII); tergite 1 (IV) much longer than tergite 2 (V), sides narrowing toward base, lacking mediobasal foveae, with pair of basolateral foveae ( Fig. 2B ; blf), short triangular discal carinae ( Fig. 2B ; dc), and broad, shallow transverse impression at base. Six sternites (III–VIII) ( Fig. 2C ; sIII–VIII) visible; sternites 1 (III) and 2 (IV) subequal in length along midline; sternite 2 (IV) lacking mediobasal foveae and basal impression, with small basolateral foveae. Foveal pattern of remaining abdominal segments barely visible based on available specimen, but one pair of basolateral foveae putatively present on each of tergites 2–4 (V–VII).

Legs moderately elongate; all three pairs of coxae contiguous; metacoxae ( Fig. 2C ; mtc) moderately projecting posteriorly; dorsal margin of all trochanters short, base of femora thus close to coxal-trochanteral articulation. Tarsi three-segmented ( Fig. 2 box; t1–3), with short tarsomere 1, and longer tarsomeres 2 and 3; tarsomere 2 distinctly shorter than tarsomere 3; tarsi each with one elongate claw ( Fig. 2 box; tc). Male mesotrochanters and mesotibiae modified on ventral margin and at near apex, respectively; fore and hind legs simple.

Etymology. The generic name is a combination of the prefix ‘ Creto -’ derived from the Cretaceous, and Brachygluta Thomson, 1859 , type genus of Brachyglutini . The gender is feminine.

Figures

Fig. 1. Habitus of †Cretobrachygluta laurasiensis gen. et sp. nov. A – dorsal view; B – ventral view. Scale bar: 0.5 mm.

Fig. 2. Morphological details of †Cretobrachygluta laurasiensis gen. et sp. nov. A – left antenna; B–D – main body parts in dorsal (B), ventral (C), and lateral (D) view, with foveal pattern and other important characters annotated. Scale bar: 0.2 mm in A; 0.5 mm in B–D. Abbreviations: a1–2, 9–11 = antennomeres 1–2, 9–11; bef = basal elytral foveae; blf = basolateral fovea; dc = discal carina; gf = gular fovea; gr = gular ridge; laf = lateral antebasal fovea; lmcf = lateral mesocoxal fovea; lmsf = lateral mesoventral fovea; lmtf = lateral metaventral fovea; maf = median antebasal fovea; mmsf = median mesoventral foveae; mp4 = maxillary palpomere 4; ms = marginal stria; mtc = metacoxa; omc = ocular-mandibular carina; p = projection; plc = posterolateral cleft; s = spur; shef = subhumeral elytral fovea; sIII–VIII = sternites III–VIII; ss = sutural stria; tIV–VIII = tergites IV–VIII; tc = pretarsal claw; ts1–3 = tarsomeres 1–3; vf = vertexal fovea.