Miniomma chenkuni Li, Yamamoto & Cai, 2020

Li, Yan-Da, Yamamoto, Shûhei, Huang, Di-Ying & Cai, Chen-Yang, 2020, A miniaturized ommatid beetle in mid-Cretaceous Burmese amber (Coleoptera: Archostemata: Ommatidae), Papéis Avulsos de Zoologia (Pap. Avulsos Zool., S. Paulo) 60, pp. 1-7 : 2

Miniomma chenkuni Li, Yamamoto & Cai sp. nov. ( Figs. 1‑4 )

Material: Holotype, NIGP173375 , sex unknown . Paratypes, OSAC _0002900274, OSAC _0002900275, OSAC _0002900276 and OSAC _0002900277, sex unknown. The specimens OSAC _0002900274-6 are in one piece of amber.

Locality and horizon: Amber mine located near Noije Bum Village, Tanai Township, Myitkyina District, Kachin State, Myanmar; unnamed horizon, mid-Cretaceous, Upper Albian to Lower Cenomanian (Mao et al., 2018).

Diagnosis: As for the genus.

Description: Body minute, 1.2-2.0 mm long, 0.4-0.7 mm wide, tuberculate, with thin setae.

Head ( Figs. 3D , 4 A-B) prognathous, moderately elongate, constricted posteriorly to form a neck; dorsal surface with Y-shaped depression (see Kirejtshuk et al., 2016), but without distinct protuberances. Temples moderately long, not prominent. Compound eyes entire and not protruding, finely facetted, without interfacetal setae. Antennal insertions lateral. Antennal grooves absent. Antenna extending beyond anterior prothoracic margin, but not reaching posterior prothoracic margin, 11-segmented and subfiliform, with thin hairs; antennomere 3 slightly longer than 4; antennomere 11 nearly twice as long as 10. Labrum transverse, with apex slightly concave. Mandible with vertically aligned teeth. Maxillary and labial palps relatively short, not reaching mandibular apex when anteriorly directed. Prementum subtrapezoidal. Gular sutures invisible.

Pronotal disc ( Fig. 4A ) longer than wide, with a shallow medial groove; anterior corners rounded. Prosternum ( Fig. 4B ) in front of coxae moderately long, probably fused with propleura. Prosternal process incomplete, apically acute. Procoxal cavities contiguous. Elytra ( Figs. 3F , 4C ) 1.7 times as long as wide combined, with rows of window punctures, probably without maculae; longitudinal ridges (primary veins) weakly raised.

Procoxae ( Fig. 4B ) subglobular. Metacoxae ( Figs.3E , 4D ) subglobular,not extending laterally. Femora stout.Tibiae thinner, without well-developed tibial spurs. Tarsi five-segmented; tarsomeres simple, not bilobed; tarsomeres 1-4 subequal in length; tarsomere 5 more than twice as long as tarsomere 4; pretarsal claws simple.

Abdomen with five coplanar ventrites, separated by wide grooves; ventrite 1 longer than others; ventrite 5 slightly longer than penultimate one, with broadly gently arcuate posterior margin.

Etymology: The species is named after Dr. Chen-Kun Jiang, a young evolutionary botanist, who helped the first author enormously on his previous research project.

Figures

Figure 1.General habitus ofMiniomma chenkuni gen.et sp.nov.,holotype,NIGP173375.(A) Dorsal view,under incident light.(B)Ventralview,under incident light. (C) Dorsal view,under widefield fluorescence.(D)Ventral view,under widefield fluorescence.Scale bars:400 μm.

Figure 2. General habitus of Miniomma chenkuni gen. et sp. nov., paratypes, under incident light. (A) OSAC_0002900274, dorsal view. (B) OSAC_0002900277, dorsal view.(C) OSAC_0002900277,ventral view.Scale bars:500 μm in (A),300 μm in (B-C).

Figure 3. X-raymicrotomographic reconstruction of Miniomma chenkuni gen.et sp.nov.,holotype,NIGP173375.(A) Habitus,dorsal view.(B) Habitus,ventral view. (C) Habitus, lateral view. (D) Head, dorsal view. (E) Hind legs and anterior portion of abdomen, with right hind leg partly removed, ventral view. (F) Left elytron, posterodorsal view.Scale bars:300 μm in (A-C),150 μm in(D-F).

Figure 4.Detailsof Miniomma chenkuni gen.et sp.nov.,holotype,NIGP173375,under confocalmicroscopy.(A) Head andanterior portion of prothorax,dorsalview, witharrowheadshowingtheY-shaped depression.(B)Head andanterior portionof prothorax,ventralview.(C)Posteriorportionof prothorax andanterior portionof elytra,dorsal view.(D)Legs andanterior portionof abdomen,ventral view.Abbreviations:an1=antennomere 1; el=elytron;ey =compoundeye;md =mandible; msf =mesofemur;mtc= metacoxa;mtf= metafemur;mttb= metatibia;mttc=metatrochanter;pc=procoxa;pf= profemur;pn= pronotum;pm =prementum; ps = prosternum;ptb = protibia;v1-2 = ventrites1-2. Scale bars:200 μm.