Damzenomyrmex ribbeckei, Radchenko, 2023

Radchenko, A. G., 2023, A New Ant Genus (Hymenoptera, Formicidae) From The Late Eocene Rovno Amber, Zoodiversity 57 (4), pp. 323-336 : 325-329

Damzenomyrmex ribbeckei sp. n.

urn:lsid:zoobank.org:act:78E0614F-20D7-492E-AFA8-39FEE721D049

Material examined. Types. Holotype, worker, No. JDC 8918 , Rovno amber, Late Eocene, Ukraine, Rivne Reg., deposited in SIZK ; paratypes: 2 workers in the same piece of amber as holotype (together with 1 worker of Lasius schiefferdeckeri Mayr, 1868 , 1 Hymenoptera sp., ca. 10 specimens of Diptera spp. in same piece of amber), deposited in SIZK ; 1 worker, No. JDC 8955 , 1 worker, No. JDC 9947 , 2 workers, No. JDC 11388 (together with 1 specimen of Blattoptera sp. in same piece of amber), Rovno amber, Late Eocene, Ukraine, Rivne Reg. ; 1 w, No. JDC 9946 , 1 worker, No. JDC 9948 , both most probably Rovno amber; all deposited in the collection of J. Damzen ( Lithuania) ; 1 worker, No. F-066 , Rovno amber, Late Eocene, Ukraine, Rivne Reg. ; 1 worker, No. F-406 (together with 3 workers of Ctenobetylus goepperti ( Mayr, 1868) in same piece of amber) ; 1 worker, No. F-613 , both Rovno amber, Late Eocene, Ukraine, Rivne Reg., Zarichniansky Distr., village Kuhotska Volya, valley of River Veselukha ; 1 worker, No. F-140 (together with 1 worker of Camponotus mengei Mayr, 1868 and termite in same piece of amber) ; 1 worker, No. F-141 , both Rovno amber, Late Eocene, Ukraine, Rivne Reg., Volodymeretsky Distr., village Voronki . Non-type: 1 worker, No. F-059 (together with 1 worker of Fallomyrma transversa Dlussky et Radchenko, 2006 in same piece of amber) ; 1 worker, No. F-142 , both Rovno amber, Late Eocene, Ukraine, Rivne Reg., Volodymeretsky Distr., village Voronki , all deposited in the collection of M. Khomych ( Ukraine).

Etymology. The species is dedicated to Mr. Hans-Werner Ribbecke ( Germany), who kindly donated the piece of amber with the holotype and two paratype specimens of this species to SIZK collection.

Workers ( figs 1–6; tables 1, 2). Body length 8.3–10.7 mm. Head ca. 1.2 times as long as wide, with distinctly convex sides and narrowly rounded occipital corners. Frontal triangle weakly defined, not separated from frons by suture, clypeus shallowly inserted between frontal lobes. Eye suboval (ratio of max/min diameters ca. 1.15), rather large (OI1 0.24–0.27, OI2 0.30), gena equal or slightly longer than maximum diameter of eyes (GI 1.00–1.11); eye without hairs. Longitudinal medial frontal groove or carina absent. Lateral frontal carina well developed, subvertical and short, somewhat sinuous and subparallel, reaching to level of midline of eye. Clypeus without medial and lateral carinae; central part of its surface convex, lateral parts lay lower than central one; clypeus in profile slightly depressed; anterior clypeal margin almost straight, without medial notch; anterolateral clypeal margin lays posterior to mediolateral margin; posterior clypeal margin lays between imaginary lines, connecting anteriormost and posteriormost surfaces of antennal sockets. Anterior tentorial pits locate near antennal sockets. Antennal scape surpassing occipital margin for ca. 1/3 of its length. First funicular segment conical, subequal to length of second one; other segments cylindrical, elongated, length of first to tenth segments ca. 3.3–4.3 times as long as wide, apical segment the longest, ca. 4.7–5.0 times as long as wide; second segment 0.90–0.96 times as long as third one; junction of third and fourth segments straight. Maxillary palp very long, reaching occipital foramen, their fifth segment the longest, ratio of length of segments 6: 5: 4 = 0.92: 1.0: 0.97; third segment subequal in length to fourth one. Labial palp rather short, fourth segment the longest, 1.6–1.7 times as long as third one, first and second segments ca. 0.5 times as long as fourth one. Mandibles rather long, ca. 0.5 times as head length.

Mesosoma slender, 3.07–3.27 times as long as high, mesonotal dorsum slightly raised above pronotum, abruptly sloping posteriorly; pronotal dorsum somewhat flattened; metanotum short, subhorizontal, separated from both mesonotal and propodeal dorsum by sutures; metathoracic spiracles situated dorsally and partly concealed by well developed tubercles. Mesothoracic epimeron near insertion with forecoxa without tooth. Dorsal surface of propodeum feebly convex, posterior one almost straight and inclined posteriorly, both surfaces of subequal length, converging at rounded angle, without teeth or tubercles. Metapleural glands well developed. Propodeal spiracles elongate-oval, less than twice as long as wide, located approximately at midlength of lateral sides of propodeum and quite close to its declivity. Petiole rather high, with long posterior peduncle, its height subequal to length; scale of medium thickness, with narrowly rounded dorsum (seen in profile), not wide, with subparallel sides, gradually rounded and convex dorsum (seen in anterior or posterior views); its anterior surface almost straight, subvertical, posterior surface slightly concave; ventral surface without lobe or tooth. Four gastral tergites visible in dorsal view. Anterior surface of first gastral tergite subvertical, gaster do not conceal petiole in dorsal view. Two apical gastral sternites with distinct longitudinal keel. Meso- and metatibiae with long simple spur, which much longer than maximum width of tibiae.

Head dorsum with 20–26 long, slightly curved coarse setae, ventral surface of head with 6–8 shorter setae, clypeus with ca. 10 setae, pronotum and mesonotum with 8–10, propodeal dorsum with 2–4 similar setae, both gastral tergites and sternites with> 20 similar setae; petiole bare; each coxa with 5–7 somewhat thinner setae; antenna without setae; femora with 3–4 setae on flexor surface, tibiae with 8–12 shorter and coarser setae on flexor surface, tarsi with numerous short coarse bristles on flexor surface. Surface of body and appendages covered with very dense silken silvery decumbent pubescence, distance between hairs much shorter than their length.

Queens and males unknown.

Measurements and indices see in tables 1 and 2.

Comparative diagnosis. Among the 28 extant genera of Dolichoderinae , Dolichoderus s. l. (= tribe Dolichoderini Forel, 1878 , see Discussion) has two autapomorphies: 1) the anterior corner of the hypostoma with expanded tooth-like flange, directed anteroventrally, and 2) the anteromedial margin of the mesosternum is convex and expanded anteriorly ( Shattuck, 1992; Shattuck & Marsden, 2013). Damzenomyrmex shares the first apomorphy with Dolichoderus s. l. ( fig. 4) (the second feature is not visible in fossil specimens, since the forecoxae must be removed to observe it). Based on this, I propose to assign Damzenomyrmex to the tribe Dolichoderini .

Modern species of Dolichoderus s. l. are highly variable morphologically. They may have denticles or spines of various shapes and lengths on the pronotum, mesonotum, propodeum, or petiole, which led to the description of a number of subgenera within Dolichoderus or separate genera in a past (see Discussion). At the same time, the posterior surface of the propodeum in the vast majority of species is concave to varying degrees. Similarly, some extinct Dolichoderus s. l. species may have differently developed denticles or spines on the mesosoma, but all of them (with one exception, see Discussion) have a distinctly concave posterior propodeal margin.

Damzenomyrmex differs well from representatives of the previously established subgenera (genera) of Dolichoderus s. l., such as Dolichoderus s. str., Karawajewella Donisthorpe, 1944 , Acanthoclinea Wheeler, 1935 , Monoceratoclinea Wheeler, 1935 and Diceratoclinea Wheeler, 1935 by the nature of the mesosomal armature (see Karawajew, 1926; Wheeler, 1935; Shattuck, 1992). It differs from the species of Hypoclinea Mayr, 1855 in the presence of horn-like projections on the anterolateral corners of the pronotum. In terms of the last character, Damzenomyrmex is similar to the species of Monacis Roger, 1862 , but differs well from them in the non-concave posterior propodeal margin, a different shape of the petiolar scale, a not laterally marginate mesonotum, and some other features (see Kempf, 1959).

Besides, Damzenomyrmex differs from all Dolichoderus s. l. species in the cuticular structure and in the serration pattern of the mandibles, with the masticatory margin having 6–7 minor sharp teeth and a much longer apical one, the basal angle distinct and the basal margin has no teeth or denticles vs. mandibles have ≥ 9 teeth with an apical tooth nearly as long as the preapical one, the basal angle is indistinct and the basal margin is serrated over the entire surface in modern Dolichoderus species. I have also observed a serrated basal margin of mandibles in a number of fossil Dolichoderus species from Late Eocene European ambers, in which the state of preservation and position in the amber allowed this feature to be seen, such as D. balticus ( Mayr, 1868) , D. tertiartius ( Mayr, 1868) , D. sculpturatus ( Mayr, 1868) , D. lucidus Dlussky, 2008 , and D. pilipes Dlussky, 2008 .

Tables

Table 1. Measurements of the holotype and paratype specimens of Damzenomyrmex ribbeckei gen. et sp. nov., in mm

No.	HL	HW	FLW	SL	OL	GL	MdL	ML	MH	PNW	PNsW	PL	PH	PW	HTL	HFL
JDC 8918H	1.87	–	–	2.16	0.51	0.51	0.94	3.24	1.04	–	–	0.65	0.65	–	2.34	2.65
JDC 8918 P-1	1.77	1.46	0.69	2.12	0.44	0.48	0.92	3.11	0.95	1.01	1.07	0.62	0.62	0.52	2.30	2.52
JDC 8918 P-2	1.72	1.43	0.66	2.13	0.43	0.47	0.91	3.17	–	1.01	1.07	0.57	–	0.52	–	–
JDK 8955	1.92	1.59	0.77	2.24	0.48	0.49	0.96	3.28	1.07	1.07	1.09	0.68	0.66	0.53	2.38	2.70
F-066	2.03	1.66	–	2.50	0.49	0.55	1.01	3.30	–	1.12	1.20	0.70	0.68	0.57	2.39	2.72
F-406	1.77	–	–	–	0.44	0.48	–	2.78	–	0.94	1.01	0.62	0.60	–	2.18	2.39
F-140	1.82	–	–	2.26	0.48	0.53	–	2.97	0.94	–	–	0.62	0.61	–	2.35	2.65
F-141	2.07	1.68	–	2.46	–	–	–	3.64	1.18	1.16	–	0.70	0.68	–	2.41	2.73
F-613	1.87	–	–	–	0.48	–	–	3.20	1.02	1.04	1.09	–	–	–	2.16	2.38

H — holotype, P-1, 2 — corresponding paratypes (see fig. 1).

Table 2. Morphometric indices of the holotype and paratype specimens of Damzenomyrmex ribbeckei gen. et sp. nov.

No.	CI	SI1	SI2	FLI	OI1	OI2	MdI	GI	PI1	PI2	MI1	MI2	FTI
JDC 8918 H	–	–	–	–	0.27	–	0.50	1.00	1.00	–	3.11	–	1.13
JDC 8918 P-1	1.21	1.19	1.45	0.47	0.25	0.30	0.52	1.09	1.00	0.29	3.27	3.06	1.10
JDC 8918 P-2	1.20	1.24	1.49	0.46	0.25	0.30	0.53	1.09	–	0.30	–	3.13	–
JDK 8955	1.21	1.16	1.41	0.48	0.25	0.30	0.50	1.03	1.02	0.28	3.07	3.07	1.13
F-066	1.22	1.23	1.50	–	0.24	0.30	0.50	1.11	1.04	0.34	–	2.95	1.14
F-406	–	–	–	–	0.25	–	–	1.09	1.04	–	–	2.97	1.10
F-140	–	1.24	–	–	0.26	–	–	1.10	1.02	–	3.16	–	1.13
F-141	1.23	1.19	–	–	–	–	–	–	1.03	–	3.08	3.14	1.13
F-613	–	–	–	–	0.26	–	–	–	–	–	3.14	3.08	1.10

H — holotype, P-1, 2 — corresponding paratypes (see fig. 1).