Mirimordella gracilicruralis, Liu, Ming, Lu, Wenhua & Ren, Dong, 2007

Liu, Ming, Lu, Wenhua & Ren, Dong, 2007, A new fossil mordellid (Coleoptera: Tenebrionoidea: Mordellidae) from the Yixian Formation of Western Liaoning Province, China, Zootaxa 1415, pp. 49-56 : 52-54

Mirimordella gracilicruralis sp. nov.

Fig. 2A–B

Holotype. No. CNU-C-LB2006201, an impression of a nearly complete mordellid in ventrolateral position rotated 10° towards the right side, with the left side fully and the right side partially exposed. It is housed in the Key Lab of Insect Evolution and Environmental Changes, College of Life Science, Capital Normal University, Beijing, China ( CNUB; Ren Dong, Curator).

Locality and horizon. Yixian Formation, Huangbanjigou, Chaomidian Village, Beipiao City, Liaoning Province, NE China.

Etymology. From the Latin prefix gracil- for being slim and Latin cruralis for leg, together referring to the relatively slim legs.

Diagnosis. In addition to the diagnosis for the subfamily and genus, the species can be diagnosed as follows: head small; eyes elongated oval, not reaching occiput; temporal angles and margins present; elytra with some longitudinal folds; elytral epipleuron small but present.

Description. Form wedge-shaped, elongate, arched, broadest behind base of pronotum. Elytra, middle femora, hind femora, and hind tibiae darker than the rest. Body, elytra, tibiae and tarsi with short pubescence. Head small, strongly deflexed, apparently constricted behind eyes to form a neck. Eyes of medium size, transversely elongated oval, not reaching occiput, slightly emarginated behind antennae. Temple distinct, with temporal angles and margins present. Labrum slightly bilobed or concave in the middle. Mandibles long and triangular from ventrolateral view. Maxillary palpi linear, with 3 visible segments, length ratio of the base segment to the terminal one 15: 8: 9, terminal one without enlargement. Antennae filiform, inserted in front of eyes, as long as or slightly longer than pronotum.

Pronotum 1.5 times as long as head; sides nearly parallel on anterior 3/4; basal angles acute, base arcuate, basal lobe short and rounded. Scutellum long, triangular or rectangular, obtusely pointed posteriorly.

Elytra arched, with some longitudinal folds, 3 times as long as pronotum, broadest from anterior 2/5 to 3/ 5, subparallel on anterior 2/3, sharply tapering caudad on apical 1/3, apex pointed. Epipleuron small, distinct on anterior 1/15 of elytra, extending apically to 1/5 of elytra. Metepisternum short, elongate rectangular. Epicoxa triangular, immediately juxtaposed to metepisternum, anterior to hind coxal plate, not separated by hind coxal plates as modern mordellids.

All tibiae and tarsi with distinct apical ridges; penultimate segments of fore and middle tarsi simple, not bilobed; claws paired, simple, not dentate. Fore and middle coxae close to each other, distant from hind coxae. Fore coxae rounded, fore trochanters invisible, fore femora slightly longer than tibiae, fore tibiae slightly increasing in width apically, fore tarsi as long as femora, length ratio of tarsi 1 to 5 8:5:5:4:4. Middle coxae rounded; middle trochanters not visible; middle femora longer than fore ones, as long as tibiae; first tarsal segment invisible, apical 4 tarsal segments of the same length. Hind coxae transversely enlarged to form an elliptical plate, small and narrow, slightly shorter and 1.5 times as broad as hind femora; hind trochanters invisible; hind femora broader and longer than fore or middle ones; hind tibiae as long as femora, slightly increasing in width apically, with oblique apices; only one apical spur visible, 1/5 as long as tarsal segment 1; hind tarsi 1.5 times as long as tibiae, length ratio of tarsi 1 to 4 15:7:6:6.

FIGURE 2. Lateral view of the holotype of Mirimordella gracilicruralis gen. et sp. nov. (CNU- C-LB2006201): A, line drawing; B, photograph.

Abdomen with 5 visible abdominal segments, sharply narrowing towards apex from the third visible segment, the lower half of the first visible abdominal segment mostly covered by the hind coxa and femur; last abdominal segment extending beyond elytral apex; last tergite without prolongation, less sclerotized than its sternite, partially missing its apex.

Measurement (mm). Body length: 6.2 (from front edge of head to tip of elytra). Head length: 1.2. Eye length: 0.6, width: 0.35. Mandible length: 0.5, width: 0.25. Length of maxillary palpal 1–3: 0.3, 0.16, 0.18. Fore leg length: femur 1.4; tibia 1.2; tarsal 1–5: 0.4, 0.25, 0.25, 0.2, 0.2; tarsal claws 0.1. Middle leg length: femur 2.0; tarsal 2–5 (segment 1 invisible): 0.4, 0.4, 0.4, 0.4. Hind leg length: coxa 2.0; femur 2.3; tibia 2.3, tibial spur 0.3; tarsal 1–4: 1.5, 0.7, 0.6, 0.6; width: coxa 0.85, femur 0.6, tibia 0.4. Pronotum length: 1.8. Scutellum length: 0.3. Elytra length: 5.5.