Eucinetus parvus, Du & Slipinski & Liu & Pang, 2020

Du, Xueyong, Slipinski, Adam, Liu, Zhenhua & Pang, Hong, 2020, Description of a new species of Eucinetidae (Coleoptera, Scirtoidea) from Cretaceous Burmese amber, ZooKeys 982, pp. 1-9 : 1

Eucinetus parvus sp. nov. Figures 1 , 2

Etymology.

Latin, parvus , meaning small, which refers to the small body size of the new species.

Holotype.

SYS-ENAM0011, female.

Locality and horizon.

Hukawng Valley, Kachin State, northern Myanmar; lowermost Cenomanian, Upper Cretaceous.

Diagnosis.

The new species can be distinguished from all the extant species of Eucinetus by the combination of the following characters: relatively small and narrower body; slenderer mesepimeron and matanepisternum; relatively short antenna with the scape shorter than pedicel. It can also be easily separated from Eucinetus nikolaevae by much smaller body (1.9 mm long compared to 2.8 mm in E. nikolaevae ), slender body-shape, and sub-rectangular labrum.

Description.

Length about 1.9 mm, width 0.7 mm. Body elongate-fusiform (Fig. 1A-C ), black, dorsum slightly convex, and covered with dense, short setae.

Head relatively small, subtriangular; posterior margin nearly truncate. Eyes moderately large, protruding, and finely facetted. Temple behind eyes moderately long; posterior angles orthogonal. Antennae closely inserted in front of eyes in antennal fossae. Antenna (Fig. 1D ) 11-segmented, short, and not extending beyond posterior margin of pronotum; scape relatively small and longer than wide; pedicel dilated and distinctly wider than adjacent segments; antennomere 3 nearly as long as following antennomeres; antennomeres 3-10 increasingly transverse toward apex; terminal antennomere larger with rounded apical margin. Frontoclypeal suture absent; labrum long, wide, and subrectangular, with nearly straight apical margin. Maxillary palp (Fig. 1D ) 4-segmented; first segment very short; palpomeres 2 and 3 subequal and cylindrical; terminal segment longest, not wider than penultimate one, and fusiform anteriorly, with sharp apex. Labium with simple prementum; labial palp 3-segmented; terminal palpomere largest and fusiform, with apex elongate and sharp.

Pronotum transverse, widest posteriorly; anterior margin broadly rounded, lateral margins gradually widened posteriorly, and posterior margins sinuate; disc with distinct microsculpture, uniformly covered by dense, short setae. Prosternum highly reduced with very narrow area in front of procoxae; prosternal process narrow. Notosternal suture present. Procoxae strongly transverse and projecting, nearly contiguous, and protrochantins exposed; procoxal cavities externally widely opened.

Elytra elongate, about 2.3 times as long as wide, lateral margins gradually narrowed posteriorly, apex sharp; dorsal surface with dense, distinct, transverse microsculpture and covered by dense, uniform setae; epipleuron not extending to apex and relatively narrow at base. Mesoventrite short, with deep, longitudinal, middle depression fitting fore femur. Mesanepisternum large and subrectangular; mesepimeron large and subtrapezoid. Mesocoxal cavities (Figs 1C , 2 ) large and subovate; laterally widely open to mesepimeron; mesocoxae moderately separated and not projecting; mesotrochantins concealed. Metaventrite short, transverse, and not narrowed towards lateral margins; metanepisternum subtriangular and elongated. Metacoxae contiguous, with large metacoxal plates covering hind femora and most of abdominal ventrite 1; metacoxal plates with anterior margin only slightly oblique, lateral margins curved. Tarsal formula 5-5-5. Abdomen with five visible ventrites, terminal ventrite subtriangular. Fore leg with small, indistinct trochanter; femur elongate and slightly curved; tibia short and flattened, gradually widened toward apex; apical spurs highly reduced; tarsi 5-segmented, with basal four tarsomeres short and almost in same length; claws small. Mid leg with small trochanter and enlarged femur; tibia flattened and broadened apically, with pair of apical spurs unequal in length; apex with fringe of small spines; tarsus with first tarsomere longest, nearly the same length as following two segments combined, tarsomeres 2-5 gradually shortened, tarsomeres 2-4 with fringe of spines apically. Hind leg (Fig. 1E ) with femur elongate and slightly dilated, mostly concealed by metacoxal plate; tibia longer than femur, flattened and widened apically, and apex with pair of short unequal apical spurs and fringe of spines; first tarsomere longest and almost same length as following two segments combined; tarsomeres 2-4 gradually shortened; last tarsomere with pair of small claws, nearly same length as penultimate one.

Figures

Figure 1. Eucinetus parvus sp. nov., holotype SYS-ENAM 0011 A, C lateral view, opposite B ventral view D head, antennae, maxillary and labial palps E hind tarsi. Scale bars: 0.5 mm (A-C); 0.2 mm (D, E).

Figure 2. Eucinetus parvus sp. nov., holotype SYS-ENAM 0011, line drawing. Scale bar: 0.5 mm.