Archaenosodendron Li & Cai, 2021

Li, Yan-Da, Tihelka, Erik, Dahan, Loïc, Huang, Di-Ying & Cai, Chen-Yang, 2021, On the Nosodendridae from mid-Cretaceous amber of northern Myanmar (Coleoptera: Nosodendroidea), Zootaxa 5082 (3), pp. 223-244 : 225-226

Genus Archaenosodendron Li & Cai gen. nov.

Type species. Nosodendron cretaceum Deng, Zhou, Ślipiński, Ren & Pang, 2018

Etymology. The generic name is composed of “ Archae- ”, ancient, and “ Nosodendron ”. The name is neuter in gender.

Diagnosis. Body elongated oval, generally less than 5 mm long. Eyes not strongly protuberant. Prosternum in front coxae not extremely shortened, longer than half length of prosternal process, with incomplete antennal grooves. Protibia expanded apically; outer edge of protibia with one row of distinct denticles. Tarsomeres slender, not distinctly lobed.

Remarks. Deng et al. (2019) originally placed N. cretaceum in the extant genus Nosodendron , since the species differs from the only other extant genus, Nosoglobulus , in having a larger body and relatively loosely articulated antennal club. They additionally noted that N. cretaceum differs from both of the extant subgenera in Nosodendron in the combination of several characters. Recently, we discovered several additional species related to N. cretaceum from Burmese amber. Based on the examination of the new materials, as well as the holotype of N. cretaceum , we suggest that the difference between this fossil group and extant Nosodendron is large enough to justify a new genus, which is herein designated as Archaenosodendron .

In extant Nosodendron (and Nosoglobulus ), the prosternum in front of coxae is extremely shortened, while in Archaenosodendron the prosternum is relatively long. More importantly, in extant Nosodendron , the lateral portions of prosternum are clearly delimited and are distinctly lower compared to the medial portion (raised mesal shelf; fig. 4B in Nomura & Kamezawa 2014), so that when in repose the fore legs can fold compactly and the protrochanters and profemora could lay exactly on the lowered lateral portions of prosternum. In Archaenosodendron , although the lateral portions of prosternum might be somewhat lowered, there is no clear and complete boundary between the lateral and medial portions, and the protrochanters and profemora are unlikely to be able to lay compactly against the prosternum.

Key to species of Archaenosodendron

- Punctures on the mentum not forming the pattern above....................................................... 2

2. Outer edge of protibia with about 14–16 relatively sparsely arranged denticles/stout setae, with the apical two distinctly stouter and more closely situated ( Fig. 11G ). Medial and lateral portions of prosternum not clearly separated ( Fig. 11D )..................................................................................... A. remotidens Li & Cai sp. nov.

- Outer edge of protibia with more denticles/stout setae; the apical two not forming the pattern above. Medial and lateral portions of prosternum separated by an incomplete ridge ( Figs 4C , 14D )................................................. 3

3. Outer edge of protibia with about 30 densely arranged denticles ( Fig. 4G–J ). Mentum with anterior angles not obviously produced ( Fig. 4A ).................................................................. A. cretaceum (Deng et al.)

- Outer edge of protibia with about 20 denticles/stout setae ( Fig. 14F–H ). Mentum with anterior angles pointed anterolaterally ( Fig. 14B )................................................................... A. angulare Li & Cai sp. nov.

Figures

FIGURE 4. Details of Archaenosodendron cretaceum (Deng et al., 2018) comb. nov., holotype, CNU-COL-MA-0321, under confocal microscopy. A, Mouthparts, ventral view. B, Antenna, ventral view. C, Prothorax, ventral view, showing the incomplete boundary between the lateral medial portions of prosternum (arrowhead). D, Abdominal base, ventral view. E, Head, anterodorsal view. F, Scutellar shield, dorsal view. G–J, Fore legs. K, Mesotarsus. L, Metatibia. Abbreviations: an8–11, antennomeres 8–11; el, elytron; hd, head; lbp, labial palp; msts, mesotarsus; msv, mesoventrite; mt, mentum; mtc, metacoxa; mtf, metafemur; mttb, metatibia; mtv, metaventrite; mxp, maxillary palp; pn, pronotum; ps, prosternum; ptb, protibia; pts, protarsus; sc, scutellum; v1–3, ventrites 1–3. Scale bars: 200 μm.

FIGURE 11. Details of Archaenosodendron remotidens Li & Cai sp. nov., holotype, NIGP177614, under confocal microscopy. A, Head, dorsal view. B, Mouthparts, ventral view. C, Antenna, ventral view. D, Prothorax, ventral view, showing the incomplete antennal groove on prosternum (arrowhead). E, Abdominal base, ventral view. F, Scutellar shield, dorsal view. G, Fore leg. H, Mesotibia and -tarsus. I, Metatibia and -tarsus. Abbreviations: an9–11, antennomeres 9–11; el, elytron; gl, galea; lbp, labial palp; md, mandible; mstb, mesotibia; msts, mesotarsus; msv, mesoventrite; mt, mentum; mtc, metacoxa; mtf, metafemur; mttb, metatibia; mtts, metatarsus; mtv, metaventrite; mxp, maxillary palp; pf, profemur; pn, pronotum; ps, prosternum; ptb, protibia; pts, protarsus; sc, scutellum. Scale bars: 200 μm.

FIGURE 14. Details of Archaenosodendron angulare Li & Cai sp. nov., holotype, NIGP177615, under confocal microscopy. A, Head, dorsal view. B, Mouthparts, ventral view. C, Antenna, ventral view. D, Prothorax, ventral view. E, Anterolateral depression of metaventrite, ventral view. F, G, Protibia and -tarsus. H, Fore and mid legs. I, Metatibia and -tarsus. Abbreviations: an9–11, antennomeres 9–11; lbp, labial palp; msc, mesocoxa; mstb, mesotibia; msv, mesoventrite; mt, mentum; mttb, metatibia; mtts, metatarsus; mtv, metaventrite; mxp, maxillary palp; pc, procoxa; pf, profemur; pn, pronotum; ps, prosternum; ptb, protibia. Scale bars: 200 μm.