Ypresiomyrma orientalis

Dlussky, G. M., Rasnitsyn, A. P. & Perfilieva, K. S., 2015, The Ants (Hymenoptera: Formicidae) of Bol’shaya Svetlovodnaya (Late Eocene of Sikhote-Alin, Russian Far East), Caucasian Entomological Bulletin 11 (1), pp. 131-152: 139-140

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Ypresiomyrma orientalis

sp. n.

Ypresiomyrma orientalis  sp. n.

( Fig. 18, 19)

Material. Holotype PIN 3429/1109 (print and counterprint), dorsal imprint of gyne without head. Paratype: PIN 3429/1198, forewing.

Description. Gyne. Judging by the remained parts body length approximately 17.5 mm. Mesosoma robust, 1.5 times as long as wide. Petiole nodiform, a little longer than wide. 1st gastral (abdominal III) segment 0.8 times as long and 0.7 times as wide as 2nd gastral (abdominal IV) segment. Forewing with closed cells1+2r, 3r, rm and mcu. Cell3r elongated, 4.5–5times as long as wide. Cell1+2r shorted, 2–2.2times as long as wide. The meeting of crossvein rs-m and RS is distal to 2r-rs, section 4RS nearly as long as cross-vein rs-m. Section 2-3RS bent to form rounded obtuse angle in its basal third and so cell rm hexogonal, twice as long as wide. Transverse rs-m position at level of pterostigma top. Section1M 2–2.5times as long as1RS. Cell mcu pentagonal. Cross-veins cu-a and section 1M meet M+Cu at the same point, essentially forming a single crossvein, so Icu=1.

Measurements, mm. Holotype PIN 3429/1109: AL6; PtL1.4; PtW1.3; FWL9.8. Paratype PIN 3429/1198: FWL9.6.

Comparison. Wing venation and short the 1st gastral segment indicate unquestionably a position of the fossils in the subfamily Myrmeciinae. The gaster lacking a constriction between the 1st and the 2nd segments in combination with a robust body are further characteristic of the genus Ypresiomyrma. The new species well differs from Y. rebekkae  in much less size of the petiolar node. No reliable difference from the North American species are found because of different (lateral) burial position of Y.bartletti and Y.orbiculata  and incomplete presentation of their wings. Yet a distinct species status of the new species is beyond doubts because all other congeners are distinctly more old (known from the Early and Middle Eocene).

Etymology. Orientalis  is the Latin for eastern.