Oncelytris, 2023

Li, Yan-Da, Huang, Di-Ying & Cai, Chen-Yang, 2023, Oncelytris esquamatus gen. et sp. nov. from mid-Cretaceous amber of northern Myanmar (Coleoptera: Lucanidae), Zootaxa 5284 (1), pp. 192-198 : 192-195

GenusOncelytris Li & Cai gen. nov.

Type species. Oncelytris esquamatus Li & Cai sp. nov.

Etymology. The generic name is a combination of the Greek “ onkos ” and “ elytron ”, referring to its exceptionally tuberculate elytra. The name is masculine in gender.

Diagnosis. Dorsal surface without scales ( Fig. 2A ). Vertex with a pair of not well-separated protuberances ( Fig. 3H ). Antennae non-geniculate, with 3-segmented, moderately lamellate club ( Fig. 3E ). Mandibles small ( Fig. 3A ). Prosternal process strongly narrowed; procoxae subcontiguous ( Fig. 3B ). Outer protibial edge with one large apical spine, one large postmedial spine, one moderately enlarged premedial spine, and numerous equal-sized small spines ( Fig. 3F ). Elytra tuberculate in posterior half ( Fig. 3I ).

Remarks. Oncelytris generally has many characters plesiomorphic in Lucanidae , such as the entire eyes not divided by canthus, non-geniculate antennae, small mandibles, and the strongly narrowed prosternal process and subcontiguous procoxae ( Kim & Farrell 2015). Among the five subfamilies, Oncelytris could be confidently ruled out from Aesalinae and Lucaninae, as the latter two have a well-developed prosternal process and well separated procoxae ( Howden & Lawrence 1974; Kim & Farrell 2015: fig. 3). Compared with Oncelytris , members of Lampriminae generally have much more developed mandibles and fewer but larger spines on protibiae.

It would be more difficult to confidently rule out Oncelytris from Syndesinae . The differentiation of subfamilies relays heavily on the male genitalic structure, and other important characters such as mandibles or antennal clubs are often sexually dimorphic ( Holloway 1960). Here we are unable to confidently determine the sex of the single specimen with genital organ unexposed. Syndesinae includes three tribes: Syndesini, Ceruchini and Sinodendrini ( Holloway 1968; Huang et al. 2011; Huang & Chen 2017a), although the monophyly of the subfamily is contentious ( Huang & Chen 2013; Kim & Farrell 2015). Nevertheless, Oncelytris could be separately differentiated from all these syndesine tribes: from Syndesini in having a 3-segmented antennal club, from Sinodendrini in frons without median tubercle or horn, and from Ceruchini in having smaller mandibles.

In general, Oncelytris is most similar to the tribe Ceratognathini of Nicaginae ( Fig. 4 ). The only other tribe in Nicaginae , Nicagini, differs from Oncelytris in having shorter antennomere 1 and protibia without numerous small spines ( Paulsen & Smith 2005). Ceratognathini includes four extant genera: Ceratognathus Westwood, 1838 , Mitophyllus Parry, 1843 , Hilophyllus Paulsen & Mondaca, 2006 and Holloceratognathus Nikolaev, 1998 ( Paulsen 2013) . The outer protibial edge of all ceratognathin genera shares a large apical spine and a large postmedial spine, but the morphology of other smaller spines varies among genera ( Holloway 1998; Paulsen & Mondaca 2006). The small spines are variablysized in Holloceratognathus , while in the remaining genera the small spines are more or less equal-sized. Mitophyllus and Hilophyllus do not have moderately enlarged spines on the proximal half of protibiae. Ceratognathus has two or three moderately enlarged spines on the proximal half of protibiae. The protibia of Oncelytris is somewhat similar to that of Ceratognathus , but with only a single moderately enlarged spine on the proximal half. Oncelytris also shares with Ceratognathus the somewhat paired protuberances on the dorsal side of head, which are absent in other genera of Ceratognathini ( Holloway 1998) .

The distinctly tuberculate elytra of Oncelytris are quite exceptional, which are unknown in any other member of Nicaginae (and even Lucanidae ). Such tuberculate elytra are reminiscent of some members of the closely related family Trogidae ( Strümpher et al. 2015; Tihelka et al. 2021; Cai et al. 2022). It is worth mentioning that the elytra of some Aesalini have a superficially similar tuberculate appearance, which, however, are due to the presence of clustered scales (e.g., Huang et al., 2015; Huang & Chen 2016, 2017b; Paulsen 2018). Oncelytris additionally differs from most Nicaginae in the absence of well-developed scales on elytra, although in the New Zealand H. passaliformis (Holloway, 1962) the elytral scales are also reduced ( Fig. 4A ; Holloway 1997).

Figures

FIGURE 2. General habitus of Oncelytris esquamatus Li & Cai gen. et sp. nov., holotype, NIGP200820, under widefield fluorescence. A, Dorsal view. B, Ventral view. Scale bars: 1 mm.

FIGURE 3. Details of Oncelytris esquamatus Li & Cai gen. et sp. nov., holotype, NIGP200820, under confocal microscopy. A, Mouthparts, ventral view. B, Prothorax, ventral view. C, Abdominal base, ventral view. D, Abdominal apex, ventral view. E, Antenna, ventral view. F, Protibia. G, Mid leg. H, Head, dorsal view. I, Elytral apex, dorsal view. Abbreviations: a1–10, antennomeres 1–10; lbp, labial palp; md, mandible; mstb, mesotibia; msts, mesotarsus; mxp, maxillary palp; pc, procoxa; ps, prosternum; ptb, protibia; v1–5, ventrites 1–5. Scale bars: 200 μm.

FIGURE 4. Extant representatives of Ceratognathini. A, Holloceratognathus passaliformis (Holloway, 1962) (male), dorsal view. © Museum of New Zealand Te Papa Tongarewa, registration number AI.000059, licensed under CC BY 4.0. B, Holloceratognathus helotoides (Thomson, 1862) (male), ventral view. C, Ceratognathus ocularis Carter, 1925 (male), ventral view.