Eocenomyrma rugosostriata ( Mayr, 1868 ) Dlussky & Radchenko, 2006

Dlussky, Gennady & Radchenko, Alexander, 2006, A new ant genus from the late Eocene European amber, Acta Palaeontologica Polonica 51 (3), pp. 561-567 : 565-566

Eocenomyrma rugosostriata ( Mayr, 1868) comb. nov.

Fig. 4 ; Tables 1, 2.

1868 Macromischa rugosostriata sp. nov; Mayr 1868: 84, pl. 4: 83, workers, Baltic Amber.

1893 Macromischa rugosostriata Mayr, Dalla Torre 1893: 120 .

1907 Macromischa rugosostriata Mayr, Handlirsch 1907: 876 .

1915 Nothomyrmica rugosostriata (Mayr) , Wheeler 1915: 61, fig. 25, workers, queen.

1995 Nothomyrmica rugosostriata (Mayr) , Bolton 1995: 292.

mesosoma

Locality and horizon: Baltic Amber, late Eocene.

Diagnosis.— Total length ca. 4 mm. This new species is characterised by the following apomorphies: frontal carinae and frontal lobes are obscure, but frontal lobes seem to be quite narrow, not extended laterally, frons quite wide; mesosoma long, not constricted behind so that propodeum not much narrower than promesonotum, metanotal groove distinct but wide and shallow (seen in profile), promesonotal suture marked (seen from above); propodeal spines of moderate length, quite wide, stout, blunt at the tips, slightly curved downwards, directed backward at an angle about 40 °, slightly divergent (seen from above); petiole distinctly longer than high, with very long peduncle, petiolar node low, long, with slightly declined Material examined.— Neotype (present designation), ZMHU F−191, worker; 1 worker, F−170, is deposited in the private collection of Manfred Kutscher , Sassnitz, Rugen, Germany; 1 worker, MZ 20234 [together with Dolichoderus tertiarius ( Mayr, 1868) and Monomorium sp. in the same piece of amber], Poland.

Diagnosis.—Total length ca. 4 mm. This species is characterised by the following apomorphies: frontal carinae are short, very weakly curved and merge with the rugae, which surround antennal sockets, frons extremely wide, frontal lobes not extended laterally; mesosoma long, constricted behind, so that propodeum much narrower than promesonotum, metanotal groove deep but wide and not abrupt, promesonotal suture marked; pronotum (seen from above) delineated by the distinct carina in front and laterally; propodeal spines of moderate length, wide and stout, slightly curved downwards apically, directed backward, and very feebly divergent (seen from above); petiole distinctly longer than high, with long peduncle, petiolar node with rounded dorsum, without dorsal plate; head dorsum with not coarse, longitudinal, subparallel, slightly sinuous rugae, without reticulation; mesosoma, petiole and postpetiole with longitudinal, slightly sinuous rugosity, without reticulation.

Eocenomyrma rugosostriata clearly differs from E. elegantula by its much coarser rugosity and lack of the reticulation on the head and mesosoma. Superficially it resembles E. electrina and E. orthospina , but differs from both by a much wider frons (FI 0.48–0.52 versus 0.39–0.42), by the narrower, not extended, frontal lobes (FLI <1.15 versus>1.20), by the lack of reticulation on the head and mesosoma dorsum, by the mesosoma constricted behind, so that propodeum much narrower than promesonotum. Additionally, it differs from E. orthospina by its distinctly downward−curved apically propodeal spines.

Remarks.— Mayr (1868: 84) described this species based on two workers from the Baltic Amber [“In der physikalisch−ökonomischen Gesellschaft (Königsberg) 1 Stück (Nr. 218), in Coll. Künow (Justizrath, Deutschland) 1 Stück (Nr. 15)”], and attributed it to the genus Macromischa Roger, 1863 (now a synonym of Temnothorax Mayr, 1861 ; see Bolton 2003). Later Wheeler (1915) transferred M. rugosostriata into his newly described genus, Nothomyrmica . He studied the queen and 10 workers (including one Mayr’s syntype), preserved in Königsberg’s ( Germany at that time, nowadays Kaliningrad in Russia) collection, described the queen and provided drawing of the worker (not of the Mayr’s syntype). At present the types of E. rugosostriata are absent in the Mayr’s collection in Naturhistorisches Museum Wien ( Ponomarenko and Schultz 1988). The most part of the Königsberg’s collection was apparently lost during the World War II, but a small part of it is preserved nowadays in the collection of the Institut und Museum für Geologie und Paläontologie der Universität Göttingen ( Germany). Based on the database of the fossils of Göttingen’s Museum no specimens of E. rugosostriata can be found there (Eugeny Perkovsky, personal communication 2004). Moreover, all our efforts to discover anything on the fate of the Künow’s personal collection were unsuccessful.

Therefore, we believe that both Mayr’s types and Wheeler’s material, belonging to this species, are lost, and we formally redescribe E. rugosostriata and designate the neotype (worker) of this species (see above). The neotype specimen wholly corresponds with the Mayr’s and Wheeler’s descriptions and drawing. Two other specimens investigated by us, are in much poorer condition, but certainly belong to this species.

Stratigraphic and geographic range.—Saxonian and Baltic ambers, late Eocene.

A Key for the identification of Eocenomyrma species:

1 Mesosoma with longitudinal, slightly sinuous rugosity ( Fig. 4 ) …….....………. E. rugosostriata ( Mayr, 1868)

– Mesosoma at least partly with reticulation ( Figs. 1–3 ) ................................................................................… 2

2(1) Whole head dorsum and mesosoma with fine reticulation; petiolar node long, with distinctly flattened dorsum ( Fig. 3 ) ….........…….…….. E. elegantula sp. nov.

– Lower and central parts of frons with longitudinal, slightly sinuous rugae, remainder part of head and mesosoma with coarse reticulation; petiolar node short, with rounded dorsum ( Figs. 1 , 2 ) ……....………………… 3

3(2) Propodeal spines thin, not widened at the base, straight, directed backward and upward; petiole with very long peduncle (PI 1.92) ( Fig. 1 ) …....................................... ................................................... E. orthospina sp. nov.

– Propodeal spines massive, widened at the base, slightly curved downward apically, directed mainly backward; petiole with much shorter peduncle (PI 1.27) ( Fig. 2 ) .................………..…….……..… E. electrina sp. nov.

Figures

Fig. 4. Myrmicine ant Eocenomyrma rugosostriata (Mayr, 1868), the neotype worker, ZMHU F−191, from the Saxonian Amber, late Eocene. A. Photograph in dorso−lateral view. B, C. Explanatory drawings, based on the original photographs; in dorso−lateral view (B), and mesosoma, waist, and gaster in lateral view (C).

Fig. 1. Myrmicine ant Eocenomyrma orthospina sp. nov., the holotype worker, MZ 13434, from the Baltic Amber, late Eocene. A. Photograph in dorso−lateral view. B, C. Explanatory drawings, based on the original photographs; head, mesosoma and waist in dorso−lateral view (B), and mesosoma and petiole in lateral view (C).

Fig. 2. Myrmicine ant Eocenomyrma electrina sp. nov., the holotype worker, ZMUC 328, from the Scandinavian Amber, late Eocene. A, B. Photograph in dorso−lateral view (A), and head and mesosoma in dorso−lateral view (B). C, D. Explanatory drawings, based on the original photographs; head, mesosoma, waist, and base of gaster in dorso−lateral view (C), and mesosoma, waist, and base of gaster in lateral view (D).

Fig. 3. Myrmicine ant Eocenomyrma elegantula sp. nov., the holotype worker, GPMHU 4404, from the Baltic Amber, late Eocene. A. Photograph in lateral view. B. Explanatory drawing, based on the original photograph; lateral view.