Priacma clavata, Tan, Jingjing, Ren, Dong & Shih, Chungkun, 2006

Tan, Jingjing, Ren, Dong & Shih, Chungkun, 2006, First record of fossil Priacma (Coleoptera: Archostemata: Cupedidae) from the Jehol Biota of western Liaoning, China, Zootaxa 1326, pp. 55-68 : 62-63

Priacma clavata sp. nov.

( Figs. 3 , 15–18 )

Diagnosis. Differs from P. serrata in the absence of spines on edge of elytra. From P. corrupta in the mesosternum of new species without cross suture, from P. longicapitis and P. oculata in the ventral head surface of new one without grooves for inserting antennae, from P. striata in the elytron of new one without paler flecks, from P. sanzii in new one’s antennal second segment shorter than third segment. P. clavata sp. nov. is distinct from P. latidentata sp. nov. and P. tuberculosa sp. nov. in the pedicel of P. c l a v a t a not less than two third of the third antennomere in length, from P. renaria sp. nov. in longer mandibles and narrower pronotum.

Description. Body length 14.0 mm, body width 3.5 mm, elytron length 10.0 mm. Medium­sized and subcylindrical beetle, covered with tubercles ( Fig. 3 ).

Head wider than long, trapeziform, bearing two pairs of tubercles, anterior pair of tubercles at base of antennae, conical, posterior ones thick, claviform, slightly larger than anterior pair; eyes large; mandibles prominent, as long as width of head, tridentate in horizontal cutting surface ( Fig. 17 ), cervical constriction weak.

Antennae filiform, incomplete (with 6 visible segments), scape thickest, pedicel about 0.8 times as long as third antennomere, following segments homonomous.

Pronotum transverse, nearly as wide as head, narrowed towards base, about 1.3 times as wide as long at posterior edge, anterior margin slightly extruding forward, anterior angles sharp ( Figs. 15 , 17 ), extending, without propleuron, disc of pronotum bearing semicircular elevation divided by longitudinal line in the middle; scutellum subtriangular.

Elytra about 2.5 times as wide as prothorax, 4.6 times as long as wide, epipleural rim narrow, veins poorly traceable, almost invisible, cells indistinct ( Fig. 15 ).

Ventral surface ( Fig. 16 ) with gula rectangular, reaching posterior ridge of the head, widening posteriorly, genae widely separated ventrally. Prosternal process extending beyond coxae. Metaventrite oblong, 0.7 times as wide as long (at posterior margin), without longitudinal suture on metaventrite ( Fig. 18 ). Abdomen with 5 visible ventrites superimposing each other, narrowed from the base of fifth visible ventrite, 2–4 visible abdomen ventrites equal in length, last visible abdominal ventrite 2.1 times as long as the previous one, its apex rounded.

Legs with procoxae elliptical, large, protrochanter sub­triangular, profemora thick, protibiae slim, nearly as long as profemora; mesocoxa round, mesotrochanter small, circular, mesotibiae slightly longer than mesofemora; metafemora short, thick, metatibiae long, metatarsi with 4 visible segments, first segment longest, following three segments homonomous ( Fig. 16 ).

Holotype. Nearly complete adult, No. CNU –C–LB2006001, housed in the Key Lab of Insect Evolution & Environment Change, College of Life Science, Capital Normal University, Beijing, China.

Locality and horizon. Collected near Chaomidian Village, Beipiao City, Liaoning Province, China; the Yixian Formation, Late Jurassic­Early Cretaceous (Late Tithonian to the Berriasian).

Etymology. The specific epithet derives from the Latin adjective clavatus, ­ a, ­ um (furnished with or fasten with nails). It refers to the shape of the tubercles on the head.

Figures

FIGURES 1 – 4. Habiti of new Priacma species, photographs of rock impressions. 1 — Priacma latidentata sp. nov., 2 — Priacma tuberculosa sp. nov., 3 — Priacma clavata sp. nov., 4 — Priacma renaria sp. nov.

FIGURES 15 – 16. Priacma clavata sp. nov., holotype. 15 — dorsal view, 16 — ventral view.

FIGURES 17 – 18. Priacma clavata sp. nov., holotype. 17 — head, 18 — metaventrite.