Cretonthophilus tuberculatus Caterino, Wolf-Schwenninger & Bechly

Caterino, Michael S., Wolf-Schwenninger, Karin & Bechly, Günter, 2015, Cretonthophilus tuberculatus, a remarkable new genus and species of hister beetle (Coleoptera: Histeridae) from Cretaceous Burmese amber, Zootaxa 4052 (2), pp. 241-245 : 242-244

Cretonthophilus tuberculatus Caterino, Wolf-Schwenninger & Bechly , n. sp.

Type material. Holotype SMNS BU- 162 (old no. F2787/Bu/CJW), deposited at the State Museum for Natural History in Stuttgart, Germany; a complete beetle of undetermined sex, preserved in a small and clear piece of Middle Cretaceous amber from Myanmar, without syninclusions. The sole specimen is remarkably well preserved, with all body parts intact, although the thorax and head are slightly distended. Some fracturing of the matrix at the posterior end of the body obscures some details of the elytral apices and pygidia, and a few small air bubbles slightly obscure some details of the ventrites.

Description. Body elongate subparallel-sided ( Fig. 1 ), darkly rufescent, with strong dorsal elytral and pronotal carinae, and lateral pronotal tubercles ( Figs. 1, 3 ); most surfaces appearing weakly encrusted with debris.

Dimensions (of holotype, in mm). Total (pronotal-elytral) length: 1.7; maximum (elytral) width: 1.05; pronotal length: 0.6; maximum pronotal width: 0.9; elytral length: 0.95; lengths of prosternum, mesoventrite, metaventrite, first visible abdominal sternite: 0.52, 0.2, 0.28, 0.25; lengths of protibia, mesotibia, metatibia: 0.42, 0.48, 0.51.

Head: frontal disk depressed at middle but strongly carinate ( Fig. 5 ), as follows: with acute, slightly longitudinal dorsomedian tubercle; complete subraorbital carina; prominent carina along anterior edge of eye; and strong, anteriorly convergent epistomal carinae; labrum about one-half width of distance between eyes, strongly protuberant, bisetose on lower surface; mandibles apically acute, sides concave; ventral mouthparts barely visible. Antennae deeply inserted beneath frontal carinae, at side of frons, adjacent to and just below midpoint of eye; scape ( Figs. 4, 5 ) rather short, narrow, carinate along anterior edge, in repose resting below antero-ventral margin of eye; pedicel cylindrical, about onethird length of scape; antennomeres 3–8 shorter, globose; antennal club setose, comprising three antennomeres, with row of short setae in distinct, complete periarticular grooves.

Dorsum: Lacking obvious scales or setae; prothorax narrowed to front, with deeply pentalobate lateral margins; dorsal disk longitudinally carinate, with incomplete lateral and sublateral basal carinae and paired, incomplete median anterior carinae rising to form acute tubercles at anterior margin. Scutellum visible, small, subquadrate; elytra with prominent humeral lobes, and three prominent dorsal carinae, more strongly elevated posterad, corresponding to the intervals between the 5th and sutural, the 3rd and 4th, and the inner subhumeral and 1st dorsal elytral striae; also with weak epipleural carina; dorsal striae appear foveate. Propygidium obscured by matrix fracturing; pygidium flat to slightly concave, fully operculate, folded beneath.

Sterna: Prosternal keel slightly emarginate at posterior margin, weakly depressed ( Figs. 3, 6 ), with longitudinal carinae slightly convergent anterad, reaching prosternal lobe, ending freely; prosternal lobe strongly produced, flat, apically emarginate, with prominent lateral alae slightly concealing antennal cavities, funicular groove broad; antennal cavities large, with well-defined margins all around, extending posterad just beyond midpoint of hypomeron, not completely closed posterad, with a notch laterad the procoxa.

Mesoventrite with prominent, acute anterior projection (inserting beneath, and not identical in shape to prosternal emargination; Fig. 6 ) and shallow anterolateral emarginations; disk apparently with small paired setose pits; metaventrite with paired setose pits near posterior margin; little else of surface sculpturing distinct, though some weak carinae and foveation are evident. First abdominal ventrite with paired setose pits mediad metacoxae; subsequent abdominal ventrites with single series of large punctures.

Legs: Procoxa globular, not strongly transverse; profemur narrowed toward apex, with weak groove on inner margin for reception of the protibia, and few recumbent setae along outer margin toward apex; protibia widened to apex, with distinct protarsal groove present along midline of distal one-third, lacking strong apical spurs, but with stout spines scattered along weakly rounded outer margin, and more densely toward apex of inner margin; tarsi 5-5-5; protarsomeres 1–4 similar in length, each with apical pair of ventral setae; protarsomere 5 about twice as long as preceding tarsomeres, lacking ventral setae; protarsal claws identical, evenly curved, about half as long as ultimate tarsomere. Meso- and metathoracic legs similar, femora narrow, elongate, tapered slightly to base and apex, weakly grooved on inner margins; tibiae somewhat abruptly widened from base, subparallel-sided to apex, flat, lacking obvious tarsal grooves, with series of stout setae along inner margins and single distinct apical spine at inner apex; tarsi rather elongate, with tarsomeres 1– 4 subequal and bearing apical pair of ventral setae, ultimate tarsomere twice as long and lacking setae, bearing pair of evenly curved claws.

Sex not determinable, because genitalia are not visible.

Type locality and horizon. Hukawng Valley (exact outcrop among the various amber mines in this valley is unknown, because the specimen was acquired from a trader), Kachin State, northern Myanmar ( Burma); Burmese amber (Burmite), lowermost Upper Cretaceous, earliest Cenomanian, 98.79 ± 0.62 mya based on U-Pb dating of zircons from the rind of unprocessed amber ( Shi et al., 2012).

Etymology. The species name refers to the prominent tubercles of the head and pronotum, particularly.

Figures

FIGURES 1 – 6. Photographs of holotype specimen SMNS BU- 162 from Cretaceous Burmese amber. 1. Dorsal view. 2. Lateral view. 3. Lateral view of prothorax, showing antennal cavity. 4. Lateral view of head and antenna. 5. Anterior view of head. 6. Ventral view of thoracic ventrites.