Scydmobisetia dentipes Jałoszyński & Bai, 2020

Jałoszyński, Paweł, Bai, Ming & Wang, Bo, 2020, A new species of the extinct mid-Cretaceous genus Scydmobisetia Jałoszyński & Yamamoto (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 4802 (3), pp. 582-586 : 583-585

Scydmobisetia dentipes Jałoszyński & Bai sp. n.

( Figs 1–12 )

Type material. Holotype: ♂, Myanmar, Hukawng Valley, Kachin State, lowermost Cenomanian, Upper Creta- ceous, inclusion in amber, collection No. NIGP173185 NIGP).

Diagnosis. Male with long tooth-like projection on proximal, ventral margin of each profemur and tuft of conspicuously long, undulating setae on subapical region of mesotibia; profemora slightly thickened in relation to meso- and metafemora.

Description. Body of male ( Figs 1–3 , 7–10 ) slender and flattened, dark brown, covered with vestiture of setae slightly lighter than cuticle. BL 1.75 mm.

Head ( Figs 4–5 , 7–10 ) broadest at small and weakly convex eyes, HL 0.28 mm, HW 0.33 mm; mandibles ( Fig. 11 ) long and slender, each with two sharp preapical mesal teeth; tempora in dorsal view about twice as long as eyes; vertex strongly transverse, weakly convex; frons confluent with vertex, flattened between weakly elevated supra- antennal tubercles. Punctures on vertex and frons distinct, dense but shallow; setae short, dense suberect; posterior margin of vertex with a pair of long, suberect bristles (one broken off in the studied specimen). Antennae ( Figs 5 , 9–10 ) long and slender, AnL 0.80 mm; antennomeres I–VII each elongate (I–V strongly so), VIII indistinctly longer than broad, IX and X each about as long as broad, XI about 1.7 × as long as broad, with asymmetrical apical half.

Pronotum ( Figs 4 , 7–8 ), broadest near anterior third; PL 0.50 mm, PW 0.43 mm. Anterior and lateral margins in anterior half rounded together, sides in posterior half sinuate, posterior corners nearly right-angled but blunt, posterior margin weakly arcuate; pronotal base with lateral pair of elongate, subtriangular impressions (median basal impression visible in Fig. 4 is not perfectly at middle and seems to be an artifact of preservation). Punctures on pronotum dense but shallow and small; setae dense, short, suberect.

Elytra ( Figs 1–3 , 7–10 ) slightly flattened, together slightly rhomboidal, broadest distinctly in front of middle; EL 0.98 mm, EW 0.58 mm, EI 1.70; humeral calli weakly marked; basal impressions shallow but distinct; apices of elytra separately rounded. Punctures on elytra dense but small and shallow; setae dense, short, suberect.

Legs ( Figs 1, 3, 6 , 7, 9–10, 12 ) moderately long and slender; trochanters unmodified, femora clavate, profemur distinctly thicker than meso- and metafemur, with distinct ventral elongate tooth-like projection at base ( Figs 4 , 12 ); tibiae slender, protibia lacking apical denticle, mesotibia with short distal denticle and tuft of several thick, conspicuously long undulating setae in subapical region, metatibia unmodified; all tarsi long and slender.

Female. Unknown.

Distribution. Cenomanian of the present-day Myanmar.

Etymology. The name dentipes refers to the tooth-like projections on the profemora.

Remarks. Scydmobisetia dentipes differs from S. vetutissima in distinctly larger body (1.75 mm vs. 1.55 mm); different proportions of pronotum (PL/PW 1.18 vs. 1.54) and elytra (EI 1.70 vs. 2.15); and in less thickened an- tennae. Males identified by Yin et al. (2018) as S. vetutissima have mesotibiae with tufts of subapical setae, but lack profemoral projections. If the holotype of S. vetutissima is in fact a female, and not a male, as identified by Jałoszyński et al. (2016) (and then the species of Yin et al. (2018) is a new one), it differs from the male of S. den- tipes sufficiently to exclude a possibility that they are conspecific. The holotype of S. dentipes has stouter elytra and pronotum, but the same relative length of antennae as the holotype of S. vetutissima (AnL/BL for holotypes of S. vetutissima and S. dentipes equals 0.46–0.47). In extant Stenichnini, females are stouter than males (i.e., they have lower pronotal and especially elytral indexes), and their antennae are relatively shorter.

The males of S. loebli and S. mengjiae , in turn, are distinctly larger than that of S. dentipes (BL of S. loebli 2.11 mm vs. 1.75 in S. dentipes ; the holotype of S. mengjiae is incomplete, but has the length of head + pronotum 0.91 mm, vs. 0.78 mm in S. dentipes ), and have clearly different leg modifications, lacking the profemoral projections.

Since the description of Scydmobisetia , a pair of considerably long vertexal setae was found also in some extant Stenichnini ( Jałoszyński 2019). However, only in the extinct Scydmobisetia these setae are conspicuously long and thick, and still (in combination with other features) represent an important diagnostic character. The number of basal elytral foveae in this genus is still unclear; one poorly visible fovea was reported by Jałoszyński et al. (2016), and putatively one fovea by Yin et al. (2018). However, in S. dentipes there seem to be two poorly visible, small basal elytral foveae. It is also confirmed that the anterior metaventral process is well-developed in Scydmobisetia , and the mesoventral intercoxal process is missing.

Figures

FIGURES 1–6. Scydmobisetia dentipes sp. n., holotype male. Left lateral (1), dorsal (2), and right lateral (3) habitus; head, pronotum and elytral bases in dorsal view (4); head in lateral view (5); and profemoral projection (arrow) in lateral view (6).

FIGURES 7–12. Scydmobisetia dentipes sp. n., holotype male. Artistic reconstruction (7); habitus in dorsal (8), right lateral (9), and left lateral (10) views; mandibles in anterodorsal view (11); and profemoral projections (arrows) in lateral view (12; one parallel to the plane of illustration, the other directed obliquely toward observer and therefore appearing shorter).Abbreviation: amvp, anterior metaventral process.