Eucinetus Germar, 1818

Li, Yan-Da, Engel, Michael S., Huang, Di-Ying & Cai, Chen-Yang, 2024, Three new species of the extant genus Eucinetus from mid-Cretaceous amber of northern Myanmar (Coleoptera: Eucinetidae), Zootaxa 5492 (2), pp. 214-230 : 215-216

Genus Eucinetus Germar, 1818

Remarks. The three new species described here have unspecialized mouthparts, distinguishing them from the genera with suctorial or semisuctorial mouthparts: Bisayodes Wakimura & Jałoszyński, Eucilodes Vit , Cretohlezkus Jałoszyński , Bisaya Reitter , Jentozkus Vit , Tohlezkus Vit and Proeuzkus Vit (e.g., Vit 1977b, 1981, 2000; Sakai 1980; Jałoszyński 2019; Jałoszyński & Wakimura 2023). The remaining “non-suctorial” group of Eucinetidae includes Eucinetella Nikitsky , Eucinetus , Nycteus Latreille , Euscaphurus Casey and Noteucinetus Bullians & Leschen. These new species differ from Eucinetella and Euscaphurus by having slender and filiform antennae, with antennomeres loosely assembled (antennae claviform to subclaviform in Eucinetella and Euscaphurus : Nikitsky 1996; Vit 1996), and from Noteucinetus in the more elongate and less convex body ( Bullians & Leschen 2004; Lawrence 2019).

Du et al. (2020) claimed that the antennomere 3 in Nycteus is distinctly shorter than the adjacent antennomeres, while in Eucinetus it is almost the same length as antennomere 4. However, according to Lawrence (2019), some Eucinetus species also have a short antennomere 3 (e.g., E. brindabellae Lawrence and E. similis Lawrence ).Actually, Nycteus could be separated from Eucinetus by the completely exposed antennal insertions and antennal grooves, U-shaped frontoclypeal suture and acute inner anterior angle of mesepimeron ( Vit 1985: figs 2, 61; Vit 1999; Lawrence 2019). The three new species all have a frontoclypeal suture straight anteriorly with distinct anterolateral angles ( Figs 3A , 7A , 11A ), which is characteristic of Eucinetus (e.g., Vit 1977a: figs 2, 4, 5; Vit 1985: fig. 60; Kim & Ahn 2008: fig. 2). Therefore, these fossils can all be assigned to the extant Eucinetus , demonstrating its considerable antiquity and remarkable stasis over the course of 100 million years of global biotic and abiotic change.

The four species of Eucinetus from Kachin amber (those described herein and the one described by Du et al. 2020) are known only from the holotypes. Two of the specimens are male, and the other two are female. To our knowledge, there is no notable sexual dimorphism in Eucinetus , except that in males one of the two mesotibial spurs is modified with a cleft apex ( Lawrence 2019). Thus, it would be justified to treat these four specimens as separate species.

Key to species of Eucinetus from Kachin amber

1. Meso- and metatibiae with relatively dense spines along the outer edge ( Fig. 11D,E ). Antennomere 3 strongly elongate ( Fig. 11A )................................................................. Eucinetus zhenhuai Li & Cai sp. nov.

- Meso- and metatibiae at most with very sparse spines along the outer edge ( Figs 3E , 7D,E ). Antennomere 3 less elongate (Figs 3A, 7A)............................................................................................. 2

2. Mesotibial spurs small; the smaller one not distinctly stouter than the spines along the apical fringe of mesotibia ( Fig. 3E )..................................................................... Eucinetus debilispinus Li & Cai sp. nov.

- Mesotibial spurs larger; the smaller one distinctly stouter than the spines along the apical fringe of mesotibia ( Fig. 7C,D )... 3

3. Metatibial spurs equal ( Fig. 7F )......................................... Eucinetus panghongae Li & Cai sp. nov.

- Metatibial spurs unequal........................................................... Eucinetus parvus Du et al.

Figures

FIGURE 3. Details of Eucinetus debilispinus Li & Cai sp. nov., holotype, NIGP203939, under confocal microscopy. A, Head, dorsal view. B, Head and prothorax, lateral view. C, Antennae. D, Meso- and metathorax, ventral view. E, Fore and mid legs. F, Hind legs. G, Scutellar shield, dorsal view. H, Elytral apex, dorsal view. I, Abdominal apex, dorsal view. Abbreviations: a1–11, antennomeres 1–11; lb, labrum; msem, mesepimeron; mstb, mesotibia; msts, mesotarsus; mtes, metanepisternum; mttb, metatibia; mtts, metatarsus; mxp, maxillary palp; pm, paramere; pts, protarsus; sc, scutellar shield. Scale bars: 100 μm.

FIGURE 7. Details of Eucinetus panghongae Li & Cai sp. nov., holotype, NIGP203940, under confocal microscopy. A, Head, dorsal view. B, Antennae. C, Mid leg. D, Fore and mid legs. E, Mid leg. F, Abdominal apex, ventral view. G, Hind leg. H, Scutellar shield, dorsal view. I, Abdominal apex, dorsal view.Abbreviations: a2–11, antennomeres 2–11; cl, clypeus; lb, labrum; mstb, mesotibia; mttb, metatibia; mtts, metatarsus; mtv, metaventrite; mxp, maxillary palp; pts, protarsus; sc, scutellar shield; v5–6, ventrites 5–6. Scale bars: 100 μm.

FIGURE 11. Details of Eucinetus zhenhuai Li & Cai sp. nov., holotype, NIGP203941, under confocal microscopy. A, Head, dorsal view. B, Antenna. C, Fore legs. D, Mid leg. E, Hind legs. F, Hind legs. G, Scutellar shield, dorsal view. H, Abdominal apex, dorsal view. I, Abdominal apex, ventral view. Abbreviations: a2–11, antennomeres 2–11; gc, gonocoxite; gs, gonostylus; lb, labrum; mstb, mesotibia; mttb, metatibia; mtts, metatarsus; mxp, maxillary palp; pts, protarsus; sc, scutellar shield. Scale bars: 100 μm.