Crematogaster primitiva

Known from a single male found in Rovno amber; Late Eocene, Priabonian stage, 33.9–37.8 Ma.

Identification
Radchenko and Dlussky (2019) - Based on the structure of the waist, mesosoma and head, as well as on the character of the forewing venation, we have no doubt that C. primitiva belongs to the genus Crematogaster. Nevertheless, it well differs from all known males of the extant Crematogaster species by its 13-segmented antennae and by its much longer antennal scape that is subequal to the total length of the 1st to 3rd funicular segments (vs. modern species, where antennae are 11- or 12-segmented and the scape length is subequal to the total length of only the 1st and 2nd segments).

With the 13 segment antenna, C. primitiva resembles the fossil Crematogaster praecursor described from the Sicilian amber (Early Oligocene, Rupelian stage, 27.8–34.9 Ma), but differs from that species by its distinctly longer antennal scape and by some details of the forewing venation.

Distribution
This taxon was described from.

Castes
Only known from the male caste.

Nomenclature

 * †. Crematogaster primitiva Radchenko & Dlussky, 2019: 418, figs. 1-2 (m). ROVNO AMBER (Ukraine, Eocene).

Male
SL 0.32, ML 1.04, MH 0.77, PL 0.32, PH 0.21, PPL 0.16, PPH 0.15, HTL 0.67, total length 3.4 mm. Ratios. ML/MH 1.34, PL/PH 1.54, PPL/PPH 1.09.

Total length ca. 3.4 mm. Head in the specimen is deformed during fossilization (flattened dorso-ventrally) but definitely small. Eyes quite big, situated approximately at midlength of sides of head. Ocelli well developed though not big. Antennae 13-segmented, without defined club, scape relatively long, subequal to total length of 1st to 3rd funicular segments. Mandibles elongate-triangular, with quite narrow but distinct masticatory margin, with is with three small acute teeth.

Mesosoma relatively high, ca. 1.3 times longer than height, scutum high, slightly convex, without Mayrian furrows. Propodeum widely rounded (seen in profile), its dorsal surface ca. 3 times shorter than posterior one. Petiole with short peduncle and massive, quite high node, its dorsum long, convex, declined anteriorly. Postpetiole small, articulated on dorsal surface of first gastral segment. Middle and hind tibiae with simple spur, pretarsal claws simple.

Forewing with closed cells 1r+2r and mcu, cell 3r open distally, cell rm is absent. Cell 1r+2r big, hexagonal, more than twice longer than width; cell mcu trapezoid (not pentagonal), ca. 1.5 times longer than width, reaching distally level of pterostigmal base. Cross-vein cu-a merging with vein section 1M+Cu far proximally than cell mcu (vein section 2M+Cu much longer than cross-vein cu-a).

Body seems smooth and shiny (sculpture on head obscured). Whole body with not abundant, quite long suberect hairs; scape with sparse decumbent pubescence; coxae, inner margins of trochanters and femora with not abundant, long erect to suberect hairs; both inner and outer margins of tibiae and tarsi with short suberect to subdecumbent hairs.

Type Material
Holotype male, Rovno amber, Late Eocene, No. K-25850 (SIZK), AntWeb CASENT No. 17566. Pugach quarry, Klesov deposit, Rovno Region, Ukraine.

Etymology
From the Latin word primitiva(feminine gender) – primitive, that means the primitive structure of the antennae compare to modern species.