Eogmelina prisca, Copilaş-Ciocianu & Ionesi, 2024

Copilaş-Ciocianu, Denis & Ionesi, Viorel, 2024, New Miocene fossil taxa illuminate the evolution and paleobiogeography of the Ponto-Caspian gammaroid amphipod radiation, Contributions to Zoology 93, pp. 268-288 : 279-280

† Eogmelina prisca gen. et sp. nov. ( fig. 6 )

LSID urn:lsid:zoobank.org:act:AFE20C61-1FEB -4C09-83B5-C57351542214

Type material. Holotype: male (inventory No. 8241 , Vlădiceni quarry), 14.8 mm, lateral impression ( fig. 6A ). Paratype: male (inventory No. 8242 , Iași City), 11.8 mm, dorso-lateral impression ( fig. 6B ). Additional material: disarticulated remains from an individual of unknown sex (inventory No. 8243 , Vlădiceni quarry), consisting of last two pereonites, al pleonites, and pereopod bases 5–7, lateral impression ( fig. 6C ).

Type locality and age. Vlădiceni quarry (47.13442 N, 27.65734 E), via Open Cryptomactra Formation , Tortonian international stage/ Bessarabian regional stage, ca. 10.5 Ma ( fig. 1C ).

Etymology. The specific epithet comes from Latin prisca meaning ancient, in reference to its lack of armature, which is considered a plesiomorphic state.

Diagnosis. See diagnosis for E. moldavica gen. et. sp. nov.

General description. Body. Relatively large and robust gammarid (up to 15 mm). Body smooth, without dorsal or lateral projections. Head length subequal to the combined length of the following two pereonites, lacking rostrum, antennal sinuses superficial, of similar depth. Coxal plates 1–3 taller than wide, taller than the corresponding tergal segments. Coxal plate 4 as tall as wide, slightly taller than corresponding tergal segment. Epimere 1 distal margin rounded, epimeres 2–3 disto-posterior corner pointed. Urosomites free and flat, devoid of tubercles or spines. Telson longer than broad, lobes oval, cleft all the way. Antennae. Antenna 1 peduncle robust and short, subequal to head length, not reaching the distal end of the 4th peduncular article of antenna 2. Peduncular segment 1 subequal to the combined length of segments 2 + 3. Antenna 2 peduncle well developed, longer than head. Gnathopods. Propodi of both gnathopods rectangular, similar in length and shape, moderately developed (0.1 of body length), palm length subequal to posterior margin. Pereopods. Pereopods 3–4 subequal in length and of similar construction, carpus linear, longer than broad, without signs of expansion. Pereopods 5–7 well developed and robust (at least 0.4 of body length), bases taller than broad, without posterior lobes, propodi subequal to carpi, dactyli moderately developed and relatively straight. Uropods. Uropod 1 rami subequal, shorter than peduncle, of senticaudatan type. Uropod 2 poorly visible, but shorter than uropod 1. Uropod 3 well developed Downloaded(0.16 from of Brill. body com 06/21 length/2024), 06: reach-25:54PM. This ing is well an open beyond access the article distal distributed end of under uropod the 1, terms both rami lanceolate longer than peduncle, endopod reaching 0.9 exopod length. Sexual dimorphism. Female unknown.

Access

Systematic remarks. The monophyly of Egomelina gen. nov. is weakly supported in ML and BA analyses, while the genus is paraphyletic in MP analyses. This is very likely due to several missing characters for E. prisca gen nov. et sp. nov. due to the incompletely preserved antennae. However, both species are closer to each other in phenetic and morphometric analyses than to the other fossil taxa. As such, we prefer to take a conservative stance and provisionally assign both species to the same genus.

Figures

FIGURE 1 Paleogeographic and geological setting.A) Map of the Ponto-Caspian region. The area marked with transparent white indicates the maximum extent of the Paratethys 11 Ma ago (Palcu et al., 2021).The green dot represents the newly discovered fossil amphipod sites from Romania, while the black dots indicate previously known fossiliferous locations from the Caucasus (Azerbaijan and Russia).B) Close-up map of Iași City, Romania, (https://www.openstreetmap.org /#map=12/47.1449/27.6062) showing the location of the study sites (Site 1 – construction site in Iași City; Site 2 – Vlădiceni quarry).C) Upper part shows a chronostratigraphic chart of the Eastern Paratethys and its correlation to the Global Time Scale (Raffi et al., 2020).The stratigraphic age of the sites from this study are indicated with green, while the previously known sites from the Caucasus are indicated with black.The lower part is a geological cross section of the focal area indicating the lithostratigraphic context and altitude (modified after Ionesi et al. 2005). Sampling sites are indicated with green dots. D) Photographs of the two study sites from the current study. PHOTO BY IONESI V.

FIGURE 6 †Eogmelina prisca gen.et sp. nov.On the right are interpretative drawings of the corresponding fossils on the left.(A) Holotype male (inventory No. 8241,Vlădiceni quarry), (B) paratype male (inventory No. 8242, Iași City), (C) disarticulated remains of unknown sex (inventory No.8243,Vlădiceni quarry).Scale bars = 1 mm.Abbreviations:A = antenna; B = basis; C = coxa; G = gnathopod; H = head; P = pereonite; PL = pleonite; PP = pereopod; U = urosomite; UP = uropod; T = telson.