Homalenchodes Li, Hsiao, Yoshitomi & Cai, 2022

LI, YAN-DA, HSIAO, YUN, YOSHITOMI, HIROYUKI, HUANG, DI-YING & CAI, CHEN-YANG, 2022, Homalenchodes, a new genus of Serropalpini from mid-Cretaceous amber of northern Myanmar (Coleoptera: Tenebrionoidea: Melandryidae), Palaeoentomology 5 (3), pp. 246-253 : 247

Genus Homalenchodes Li, Hsiao, Yoshitomi & Cai gen. nov.

Type species. Homalenchodes jarzembowskii sp. nov.

Etymology. The generic name is a combination of the Greek “ homalós ”, smooth, referring to the absence of longitudinal striae on its elytra, and “ Enchodes ”, a presumably closely related genus. The name is feminine in gender.

The generic name Enchodes LeConte has been sometimes mistakenly treated as masculine (e. g., Jung, 2019). According to Article 30.1.4.4 of ICZN (1999), “a compound genus-group name ending in the suffix - ites, - oides, - ides, - odes, or - istes is to be treated as masculine unless its author, when establishing the name, … treated it as such by combining it with an adjectival species-group name in another gender form”. When establishing genus Enchodes, LeConte (1866) added a single previously described species, Dircaea sericea Haldeman , citing it as Enchodes sericea (Haldeman) . Thus, the name should be feminine in gender.

Diagnosis. Body relatively small, strongly elongate. Compound eyes coarsely facetted ( Fig. 2A, B ). Antennae long, filiform. Maxillary palps simple ( Fig. 2A ). Pronotum widest posteriorly, with somewhat produced posterior pronotal angles ( Fig. 2B ). Prosternal process complete, gradually narrowed posteriorly, slightly extending beyond posterior procoxal margin ( Fig. 2A ). Procoxae narrowly separated ( Fig. 2A ). Protrochantins well exposed ( Fig. 2A ). Elytra without longitudinal striae ( Fig. 2E ). Meso- and metatibiae without transverse rows of bristles or spines ( Fig. 2D ). Metatibial spurs normal-sized (distinctly shorter than half length of metatarsomere 1) ( Fig. 2D ). Penultimate tarsomeres ventrally lobed in all three pairs of legs ( Figs 2C , 3 ).

Remarks. Homalenchodes shares with Synchroidae a similar elongate habitus, lateral and oval eyes, and transverse head and pronotum. In fact, the adults of Synchroidae have an appearance similar to Melandryidae , but these two families are otherwise readily separable based on larval characters ( Crowson, 1966). Nevertheless, synchroids are generally characterised by the long interfacetal setae (absent in Mallodrya Horn , although this genus might have been inappropriately placed in Synchroidae and needs to be further evaluated; Hsiao et al., 2018), unmargined posterior edge of pronotum (distinctly margined in Mallodrya ), prosternal process markedly extending beyond procoxae with long oval apex (prosternal process laminate, ending just before the posterior edges of procoxae in Mallodrya ), and unlobed penultimate tarsomeres ( Ślipiński & Lawrence, 2010; Hsiao et al., 2018), while Homalenchodes has no interfacetal setae, a margined posterior edge of pronotum, a posteriorly gradually narrowed prosternal process with acute apex, slightly extending beyond posterior edges of procoxae, and lobed penultimate tarsomeres. Therefore, here we believe that it is appropriate to place Homalenchodes in the (currently non-monophyletic) family Melandryidae .

Figures

FIGURE 2. Details of Homalenchodes jarzembowskii Li, Hsiao, Yoshitomi & Cai gen. et sp. nov., holotype, NIGP180475, under confocal microscopy. A, Head and prothorax, ventral view. B, Head and prothorax, dorsal view. C, Abdominal base and fore leg. D, Abdominal apex and metatibia, ventral view. E, Elytral apex, dorsal view. Abbreviations: an1–9, antennomeres 1–9; el, elytron; ey, compound eye; lbp, labial palp; md, mandible; mstb, mesotibia; msts, mesotarsus; mtc, metacoxa; mttb, metatibia; mtv, metaventrite; mxp, maxillary palp; pc, procoxa; pf, profemur; pn, pronotum; ps, prosternum; ptb, protibia; ptcn, protrochantin; pts, protarsus; v1–5, ventrites 1–5. Scale bars: 200 μm.

FIGURE 3. Details of Homalenchodes jarzembowskii Li, Hsiao, Yoshitomi & Cai gen. et sp. nov., holotype, NIGP180475, under confocal microscopy. A, Mesotarsus, lateral view. B, Metatarsus, dorsal view. C, Metatarsus, ventral view. Abbreviations: mst1–5, mesotarsomeres 1–5; mtt1–4, metatarsomeres 1–4. Scale bars = 100 μm.