Eocenomyrma

Dlussky, Gennady & Radchenko, Alexander, 2006, A new ant genus from the late Eocene European amber, Acta Palaeontologica Polonica 51 (3), pp. 561-567 : 562-563

Genus Eocenomyrma nov.

Type species: Eocenomyrma orthospina sp. nov.

Derivation of the name: After the Eocene, time when it existed, and Greek myrmex —ant.

Diagnosis.—Clypeus short and broad, with two lateral longitudinal carinae and distinctly marked anterolateral corners, its median portion faintly concave transversally, anterior margin broad and shallowly concave; pairs of long setae situate on the anterolateral clypeal corners, central part of the anterior clypeal margin without setae (the latter features are not visible in all described species); clypeus posteriorly broadly inserted between frontal lobes; frontal lobes broad, anteriorly reaching or even surpassing anterior clypeal margin; maxillary palps with 4, labial palps with 3 segments (this feature is visible only in Eocenomyrma rugosostriata ); antennae 12−segmented, with the remarkable 3−segmented apical club, which is clearly separated from the rest of funiculus; middle and hind tibiae are lacking spurs; body (except the gaster) distinctly sculptured (rugose and/or reticulate), not smooth; mesosoma with distinct metanotal groove; propodeum is with quite long spines; eyes well developed, big.

Eocenomyrma is superficially similar to some ant genera, both extinct and extant, particularly to the Myrmica and Temnothorax Mayr, 1861 (see also Bolton 2003), but clearly differs from them in the peculiar shape of the clypeus: in Myrmica and Temnothorax the median portion of clypeus is convex or somewhat flattened, but never concave transversally, without lateral longitudinal carinae and marked anterolateral corners; anterior clypeal margin is rounded or somewhat prominent, occasionally shallowly notched medially. In addition, the majority of the extinct and extant Myrmica and Temnothorax species have a well−developed spur on the middle and hind tibiae, absent from the new genus.

Eocenomyrma has palp formula 4, 3 versus 6, 4 in Myrmica , what precludes their close relationship.

Remarks.—Based on the tribal characters of the subfamily Myrmicinae proposed by Bolton (2003), we suggest to include Eocenomyrma in the tribe Formicoxenini . As mentioned above, Eocenomyrma most likely is related to Temnothorax , and its peculiar clypeal structure may be considered as the apomorphy; lack of tibial spurs also can be regarded as apomorphy, however apomorphies by reduction are much less significant evolutionary. On the other hand, Eocenomyrma has some plesiomorphic (regarding to Temnothorax ) features, particularly Myrmica −like structure of head and frontal lobes, general shape and sculpture of the body, etc. We suggest that Eocenomyrma most probably did not arise from any extant Formicoxenini genera, but has common ancestor with them, including Temnothorax .