Derolathrus capdoliensis, Tihelka & Peris & Cai & Perrichot, 2022

Tihelka, Erik, Peris, David, Cai, Chenyang & Perrichot, Vincent, 2022, A Jacobson’s beetle from Cretaceous Charentese amber (Coleoptera: Jacobsoniidae), Geodiversitas 44 (3), pp. 47-56 : 50

Derolathrus capdoliensis n. sp.

( Figs 2-5 )

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HOLOTYPE. — IGR.CDL-2.42 , slightly distorted specimen, sex indeterminate ( Fig. 2 ). Deposited in the Geological Department and Museum of the University of Rennes, France.

ETYMOLOGY. — Derived from ‘ Capdolium ’, the latin name of the type locality Cadeuil.

TYPE LOCALITY. — Charentese amber; lithological horizon A1b from Cadeuil quarry at Sainte-Gemme, Charente-Maritime department, France.

AGE. — Early-Late Cretaceous, latest Albian-earliest Cenomanian.

DIAGNOSIS. — Head subglabrous, without deep setiferous punctures. Antennae 11-segmented, apical two antennomeres not completely fused. Antennomere 10 slightly broader and shorter than the following segment, antennomere 11 pointed apically. Eyes large, with c. 30 ommatidia, their diameter slightly greater than the distance from their anterior margin to the antennal insertions. Pronotum rather parallel-sided, broadest in the anterior quarter. Pronotal disc with an oval medial depression with a raised longitudinal groove. Femora distinctly clavate.

DESCRIPTION

Body minute, subcylindrical, narrowly elongate. Length from clypeus to apex of the preserved part of abdomen 0.76 mm, 0.22 mm wide across the broadest point of the elytra. Body subglabrous dorsally, dark brown to black ( Figs 2 ; 3 ).

Head oval, 0.2 mm long from clypeus to distalmost part of the neck, abruptly constricted behind the eyes and with a distinct neck region, slightly fractured. Head surface glabrous, lacking carinae, raised ridges or deep punctures. Mandibles small, slender, curved. Maxillary palpomeres three-segmented, with apical palpomere aciculate and the penultimate palpomere distinctly larger, approximately three times the length of the following segment and broadest in the basal third. Eyes oval, somewhat protruding, multifaceted, and consisting of approximately 30 ommatidia. Antennae 11-segmented, concealed from above and inserted anterior to the eyes, separated by slightly less than the diameter of the eyes. Antennomere 1 (scape) globular, approximately as long as wide, antennomere 2 (pedicel) 0.9 times as long and 0.8 times as wide as the preceding segment, more elongate and barrel shaped; antennomeres 3-9 moniliform, gradually shortening and widening apically, antennomeres 10-11 forming a compact club; antennomere 10 0.9 times as long and 1.1 times as broad as the following segment, widest apically; 11 pointed apically ( Figs 4 ; 5 ). Temples short, less than a quarter of the length of the eye.

Pronotum slightly distorted, 0.19 mm long, 1.1 times longer than wide, slightly wider than the head, approximately parallel-sided. Widest in anterior quarter. Anterior pronotal angles rounded, posterior pronotal angles obtuse. Pronotal disc with an oval medial depression with a raised longitudinal groove running from the basal quarter to the anterior quarter ( Fig. 5A : pd, pg). Ventral side of pronotum strongly deformed. Procoxae globular, separated by approximately a third of their diameter across the broadest point. Mesocoxae rounded, further apart than procoxae, separated by more than half of their diameter. Metaventrite 0.24 mm long, broadening posteriorly and wider than head. Scutellum not visible.

Legs short, slender with the exception of the apically swollen femur. Trochanters distinctly large, trapezoidal. Femora broadened, clavate ( Fig. 5B ). Tibiae slender, twice as broad in apical half as at base, lacking apical spurs. Tarsus 3-segmented, third tarsomere longer than the basal two segments combined. Claws simple, empodium not apparent.

Elytra incomplete, narrower than pronotum basally,smoothly broadening towards the middle, and narrowing apically. Hind wings present, venation strongly reduced, ventral margin with approximately 30 elongate setae, dorsal margin with about 30 minute setae.

Abdomen poorly preserved, apical portion apparently missing. Intercoxal process of ventrite 1 broadly rounded.

Figures

FIG. 2. — Holotype of Derolathrus capdoliensis n.sp.(IGR.CDL-2.42) in dorsal view:A, under normal reflected light;B, under green fluorescence.Scale bars:200 μm.

FIG. 3. — Morphological details of the holotype of Derolathrus capdoliensis n. sp. (IGR.CDL-2.42) in dorsal view under green fluorescence. Abbreviations: a10-11, antennomeres 10-11; ey, eye;hw, hindwing;md, mandible;mp, maxillary palpomeres;nc, neck region;pr, pronotum;t3, protarsomere 3.Scale bar:100 μm.

FIG. 4. — PPC-SRμCT reconstruction of the holotype of Derolathrus capdoliensis n. sp. (IGR.CDL-2.42): A, ventral view; B, dorsal view. Scale bar: 200 μm.

FIG. 5. — Enlargement of the PPC-SRμCT reconstruction details of the holotype of Derolathrus capdoliensis n. sp. (IGR.CDL-2.42):A, dorsal view;B, ventral view. Abbreviations: mfe, mesofemur; mtv, metaventrite; pg, pronotal groove; pca, procoxa; pd, pronotal depression; pti, protibia; tr, trochanter. Scale bar: 200 μm.