Aphaenogaster ribbeckei Radchenko, 2024

Radchenko, A. G., Gröhn, C. & Ribbecke, H. - W., 2024, Two New Aphaenogaster Species (Hymenoptera, Formicidae) From Baltic Amber, Zoodiversity 58 (3), pp. 195-202 : 198-200

Aphaenogaster ribbeckei Radchenko , sp. n. ( figs 2 , 3 )

urn:lsid:zoobank.org:act:840AAFA8-8BC1-40AF-8FAF-F56C050A7ABF

M a t e r i a l e x a m i n e d. Holotype worker, complete specimen, No. GPIH 5204 , Baltic amber, Late Eocene, Poland (LIB).

Etymology. The species is dedicated to Mr. Hans-Werner Ribbecke ( Germany), who provided the piece of amber with the holotype specimen of this species for investigation.

Worker ( figs 2 , 3 ). Body length 5.2 mm. Head elongated, HL/HW 1.24, subrectangular, with feebly convex sides, with well marked and narrowly rounded occipital corners, occipital margin slightly convex and delineated by distinct ridge. Anterior clypeal margin feebly convex, with medial notch. Frontal carinae short, feebly curved, subparallel, frons narrow, 0.30 times of head width, frontal lobes slightly extended, 1.12 times as wide as frons. Scape of moderate length, subequal to head length, exceeding occipital margin by ca. 1/4 of its length, very feebly curved at base and gradually widened to apex; funiculus with quite well defined 4-segmented club; 2 nd to 6 th funicular segments moderately elongated, ca. 1.5 times as long as wide. Eyes of moderate size, their maximum diameter 0.20 times the head length and 1.55 times their minimum diameter, situated somewhat in front of sides of head, 0.86 times as long as gena. Dentition of mandibles obscured.

Mesosoma very long and slender, about 3.7 times as long as height and more than three times as long as pronotal width. Mesonotal dorsum distinctly raised over pronotal level, so that promesonotal dorsum does not form regular arch, promesonotal suture well marked dorsally, pronotum widely rounded anteriorly, but humeri with short and pointed triangular denticles, directed backward. Promesonotal dorsum strongly convex, mesonotum posteriorly and propodeal dorsum somewhat flattened, metanotal groove distinct and quite deep, propodeal lobes projecting apically, but not pointed. Propodeum with relatively long pointed spines, directed backward and upward at an angle ca. 45 o and moderately divergent. Petiole very long and thin, 1.65 times as long as height, about 0.5 times as long as head, and more than 3 times as long as width; anterior surface of petiolar node very feebly concave, subvertical, posterior one very feebly convex, abruptly sloping posteriorly, anterior and posterior surfaces converge at an acute angle, so that node seems cuneiform (seen in profile). Postpetiole about 1.3 times as long as height and about 1.4 times as wide as petiole, its node somewhat flattened. Legs long and slender, meso- and metafemora strongly swollen.

Head dorsum with coarse reticulation, lateral sides of head with dense longitudinal rugosity. Lateral sides of mesosoma with coarse longitudinal rugosity, mesosomal dorsum with coarse reticulation. Surface between rugae densely punctated, but appears somewhat shiny. Petiole and postpetiole appear punctated, but shiny. Appendages and gaster smooth and shiny.

Whole head with numerous, quite long and rather coarse erect setae. Promesonotal dorsum with at least 20 similar setae, propodeal dorsum with two pairs of shorter setae, petiolar node with two pairs of long setae, postpetiole with about 10 similar setae. First gastral tergite and sternite with numerous setae, remainder sternites with much less abundant setae, remainder tergites non-setose. Decumbent pilosity on body absent. Scape with short subdecumbent pilosity, inner surface of femora with a few quite long suberect setae, tibiae and tarsi with abundant short subdecumbent pilosity.

Gynes and males unknown.

Measurements (in mm) and ratios: HL 1.01, HW 0.82, SL 1.08, FW 0.25, FLW 0.28, OL 0.20, OW 0.13, GL 0.23, ML 1.53, MH 0.42, PnW 0.49, PL 0.49, PH 0.30, PW 0.16, PPL 0.30, PPH 0.23, PPW 0.21, HTL 0.79, HFL 1.27, ESL 0.17, ESD 0.25.

HL/HW 1.24, SL/HL 1.06, SL/HW 1.32, FW/HW 0.30, FLW/FW 1.12, OL/HL 0.20, OL/OW 1.55, OL/GL 0.86, PL/ PH 1.65, PL/PW 3.17, PL/HL 0.49, PW/HW 0.19, PPL/PPH 1.28, PPW/PW 1.38, PPW/HW 0.26, ESL/HL 0.17, ESL/HW 0.21, ESD/ESL 1.46, ML/MH 3.69, ML/PnW 3.11, HTL/ML 0.60, HFL/ML 0.83.

C o m p a r a t i v e d i a g n o s i s. For the differences from A. groehni see above. A. ribbeckei differs well from other previously described Aphaenogaster species from the Late Eocene European ambers primarily by the much more slender mesosoma and waist, in particular, ML/MH 3.7 vs. <3.0, PL/PW 3.2 vs. <2.2. By the shape of promesonotum A. ribbeckei resembles A. sommerfeldti , but differs by this feature from other amber species. In addition, it differs from A. oligocenica by the longer and pointed propodeal spines, and from A. antiqua — by the longer scape and funicular segments.

Figures

Fig. 2. Photos of Aphaenogaster ribbeckei Radchenko, sp. n., holotype, worker, body in lateral view. Scale bar 1 mm.

Fig. 3. Photos of Aphaenogaster ribbeckei Radchenko, sp. n., holotype, worker, body in dorsal view. Scale bar 0.5 mm.