Cretakarenni shaoi Li & Cai 2022, sp. nov.

Cretakarenni shaoi Li & Cai, sp. nov. (Figs 1–6)

Material examined. Holotype, NIGP177331, probably male.

Etymology. The species is named after Mr. Yiwei Shao, who kindly donated many valuable fossils for our research.

Locality and horizon. Amber mine located near Noije Bum Village, Tanai Township, Myitkyina District, Kachin State, Myanmar; unnamed horizon, mid-Cretaceous, probably Lower Cenomanian.

Diagnosis. Paired setose projections on vertex narrowly separated (by less than one fifth of maximum head width including eyes) (Figs 4G, 6D). Elytral absutural lines absent (Fig. 4I).

Description. Adult male. Body elongate, 1.67mm long, 0.58 mm wide, covered with distinct setae.

Head (Figs 4G, 6C–D) prognathous, posteriorly constricted to form a neck; vertex with a pair of narrowly separated setose projections. Compound eyes lateral, entire, well-developed with many facets. Frontoclypeal suture absent. Antennae (Fig. 4B) apparently 10-segmented; antennal club distinct, apparently 1-segmented. Antennal cavities (subantennal grooves) present, converging posteriorly (Fig. 6C). Mandibles (Figs 4A, 6D) short and broad, unidentate apically; incisor edge simple, not dentate. Maxillary palps 4(?)-segmented. Labial palps 3-segmented.

Pronotal disc slightly transverse, widest near middle, without impressions; lateral margins slightly curved, smooth; anterior angles broadly rounded, not projecting. Prosternum in front of coxae broad, transverse (Fig. 4C); prosternal process narrower than procoxal cavity width, with a weak longitudinal ridge medially, expanded apically (Fig. 4C). Procoxal cavities externally closed, distinctly transverse (Figs 4C, 6A–B). Protrochantins exposed (Fig. 4C).

Scutellum with two pairs of setae (Fig. 4H). Elytra truncate apically, not fully covering abdomen (Fig. 4I); elytral absutural lines absent (Fig. 4I). Mesocoxal cavities (Fig. 6A) open, laterally bordered by mesepimeron; distance between mesocoxal cavities narrower than mesocoxal cavity width. Metaventrite broad. Metanepisternum elongate.

Tibiae with distinct apical spurs. Tarsi 5-5-4 (Fig. 4E); basal three (or two in hind legs) tarsomeres with dense hairs; apical two tarsomeres distinctly thinner than basal ones, subglabrous; apical tarsomeres distinctly longer than preapical ones.

Abdomen with 6 ventrites. Ventrite 1 longest, as long as ventrites 2–4 combined (at middle); intercoxal process of ventrite 1 broadly rounded (Fig. 4F).

Remarks. Sexual dimorphisms have been known in both extant (Sen Gupta, 1988; Liu et al., 2020) and extinct (Jiang et al., 2019; Liu et al., 2020) monotomid beetles. Generally females have 5-segmented metatarsi and five abdominal ventrites, while males have 4-segmented metatarsi and six abdominal ventrites. In Cretakarenni birmanicus, the head of the male is armed with a pair of setose projections (Jiang et al., 2019), while the female has an unmodified head (Peris & Delclòs, 2015). The new specimen studied here possesses 4-segmented metatarsi, six ventrites, and paired setose projections on head, thus it is of high probability to be a male, even though the genitalia are not exposed.