Electroxylita, Alekseev & Bukejs, 2021

Alekseev, Vitalii Igorevich & Bukejs, Andris, 2021, Fossil Melandryidae (Coleoptera: Tenebrionoidea) from Eocene Baltic amber of the Sambian peninsula: new genus, six new species, new records and key to described taxa, Zootaxa 4965 (1), pp. 142-166 : 143-144

Genus Electroxylita gen. nov.

Type species: Electroxylita chronographica sp. nov., here designated.

Note. The newly described fossil taxon, Electroxylita gen. nov., possesses typical external morphological characters of the tribe Xylitini within the subfamily Melandryinae : procoxae contiguous, pretarsal claws simple, 11-segmented antennae short and filiform, base of pronotum closely associated with elytral base, head concealed from above, lateral and basal edges of pronotum margined, lateral pronotal sides carinate, pronotum without impressions at base, notosternal sutures distinct but non-carinate, penultimate tarsomere of pro- and mesotarsi widened, meso- and metatibial spurs equal in lengths and comparatively short, tibiae without ridges, protrochantin visible, metatarsomere 1 long etc. However, Electroxylita gen. nov. does not fully correspond to any extant genus of the tribe, and therefore it is placed into a new genus.

Differential diagnosis. The tribe Xylitini , consists of 5–6 extant genera ( Nikitsky & Pollock 2010), namely Xylita Paykull, 1798 , Rushia Förel, 1893 , Dolotarsus Jacquelin du Val, 1863 , Scotochroa LeConte, 1874 (which may be synonymous with Dolotarsus ), Scotochroides Mank, 1939 , and Spilotus LeConte, 1862 . Electroxylita gen. nov. differs from Xylita , Rushia , Dolotarsus , and Scotochroa in conical antennomeres distinctly longer than wide. The newly described genus can be distinguished from Rushia , Spilotus , and Xylita by the comparatively short prosternum before proxocal cavities, from Rushia by the anteriorly converging lateral pronotal margins, from Scotochroa by the shape of apical maxillary palpomere, from Xylita by the separate mesocoxae and transverse pronotum, from Scotochroides by shorter and not so robust antennae, from Spilotus in procoxal cavities with distinct fissure, unicolorous elytra, and weakly bisinuate pronotal base.

The oldest geological record of the family Melandryidae is Archaeoxylita zherichini Nikitsky 1977 from Lower Cretaceous (Santonian) Taimyr amber ( Nikitsky 1977). The original description of Archaeoxylita lacks tribal placement, but the genus corresponds to the tribe Xylitini in reported characters (procoxae contiguous, penultimate tarsomere widened, large and cultriform ultimate maxillary palpomere, non-striate elytra etc.). The Cretaceous beetle resembles the recent genus Rushia and strongly resembles Xylita according to original diagnosis and comparison ( Nikitsky 1977). The Baltic amber Electroxylita gen. nov. differs from Archaeoxylita in relative length ratios of metatarsomeres, in comparatively non-widened antennomeres 9 and 10, in larger body size (body length of Archaeoxylita zherichini is about 2 mm).

Additionally, Electroxylita gen. nov. differs from extant representatives of the tribe in the following combination of characters: (1) small body size (extant representatives are mostly larger than 6 mm), (2) large apical maxillary palpomere (longer than palpomeres 1–3 combined), (3) short portion of prosternum before procoxae; and (4) uniform and very fine pronotal and elytral punctuation.

Etymology. The name of the new genus is a compound word: “electron” (ancient Greek word for amber), and “ Xylita ” (name of the type genus in the tribe). The gender is feminine.

Remarks. The new genus is monotypic, represented by the type species only. Therefore, the generic description considerably overlaps that of the species.