Drymomyrmex rasnitsyni, Radchenko, 2021

Radchenko, Alexander G., 2021, New species of the fossil ant genus Drymomyrmex (Hymenoptera, Formicidae, Formicinae) from the late Eocene Rovno amber (Ukraine), Palaeoentomology 4 (6), pp. 544-549 : 545-546

Drymomyrmex rasnitsyni sp. nov.

( Figs 1–3 )

Holotype. Worker, SIZK No. DO-136, Ukraine, Rovno Prov., Dubrovitsy Distr., village Osova , Rovno amber, late Eocene.

Etymology. The new species is named in honour of Professor Alexander P. Rasnitsyn, famous Russian paleoentomologist.

Diagnosis. Head elongated; antennae 11-segmented; mesonotum completely fused with metanotum and the latter does not form a distinctly separate sclerite; meso- and metatibiae with well developed simple spurs.

Type locality and horizon. Ukraine, Rovno Prov., Dubrovitsy Distr. , village Osova , Rovno amber, late Eocene, Priabonian, 33.9–37.8 Ma.

Description. Total length ca. 3.5 mm. Despite head width not properly measurable, head definitely elongated, seems at least ca. 1.4 times as long as wide; sides of head very slightly convex, subparallel, occipital corners narrowly rounded, occipital margin straight. Antennae 11-segmented, inserted to head just near posterior margin of clypeus; scape relatively short, slightly does not reach occipital margin; funicular segments gradually enlarged from 2 nd to apical, 1 st segment ca. twice as long as wide, 2–5 th transversal, 6–9 th subsquare, 10 th the longest, ca. 1.5 times as long as two preceding segments together. Eyes of moderate size (OI 0.26), situated approximately at midlength of sides of head, genae distinctly longer than maximum diameter of eye (GI 1.29). Ocelli absent. Surface of median portion of clypeus evenly convex, not truncated anteriorly over mandibles, its anterior margin feebly convex. Frontal carinae very short, not reaching level of anterior margin of eyes, clypeus not inserted between frontal carinae; anterior part of frons with not coarse longitudinal carina (instead of groove); frontal triangle small, but distinct. Mandibles triangular, but obscured, number of teeth cannot be counted. Maxillary and labial palps not visible.

Mesosoma relatively stout, ca. 1.3 times as long as high, pro-mesonotal suture very clear and deep, mesonotum slightly raised above pronotum, inclined to propodeum; mesonotum fused with metanotum, so that metanotum does not form distinctly separate sclerite (seen from above); propodeal dorsum much lower than promesonotum (i. e., mesosoma does not form regular arch in profile); propodeum gradually rounded, without teeth or tubercles, its dorsal surface somewhat shorter than declivous one; propodeal spiracles rounded, located quite close to declivity. Petiole with short posterior peduncle, its scale slightly inclined forward, thick, relatively low, with subparallel anterior and posterior surfaces and widely rounded dorsum; gaster partially overhangs posterior petiolar peduncle. Metacoxae widely separated (seen from below). Legs of moderate length, fore femora quite wide, ca. 3 times as long as width; middle and hind tibiae with well developed simple spur, which longer than maximum width of tibia; pretarsal claws simple.

Head dorsum and appendages with short and relatively sparse decumbent pubescence, length of appressed hairs subequal to distance between them, but such pubescence much denser in ventral and lateral surfaces of head, mesosoma and gaster, where hairs much longer than distance between them. Frons and occiput with infrequent quite long erect to suberect hairs, occipital margin and margin of temples also with very dense short subdecumbent hairs; mesosoma and petiole with rather long, often curved erect to suberect hairs, gaster with similar, but shorter hairs; antennae and legs with numerous quite short subdecumbent hairs, tarsi additionally with numerous coarse bristles. Body and appendages brownish-black.

Gynes and males. Unknown.

Measurements (in mm). HL 0.69, SL 0.49, OL 0.18, GL 0.23, ML 0.98, MH 0.43, HTL 0.74.

Indices: SI 0.72, OI 0.26, GI 1.29, MI 2.27.

Figures

FIGURE 1. Photographs of Drymomyrmex rasnitsyni sp. nov., holotype, SIZK No. DO-136. A, Anterolateral view. B, Left dorsolateral view. C, Right dorsolateral view.

FIGURE 2. Photograph of piece of amber with the holotype worker of Drymomyrmex rasnitsyni sp. nov.

FIGURE 3. Line drawings of Drymomyrmex rasnitsyni sp. nov., holotype. A, Head, dorsal view. B and C, Right dorsolateral view.