New Miocene fossil taxa illuminate the evolution and paleobiogeography of the Ponto-Caspian gammaroid amphipod radiation Author Copilaş-Ciocianu, Denis 0000-0002-6374-2365 Laboratory of Evolutionary Ecology of Hydrobionts, Nature Research Centre, 08412 Vilnius, Lithuania denis. copilas-ciocianu @ gamtc. lt denis.copilas-ciocianu@gamtc.lt Author Ionesi, Viorel 0000-0003-0122-3655 Department of Geology, Alexandru Ioan Cuza University of Iași, Iași 700506, Romania RECEIVED 1 FEBRUARY 2024; REVISED 12 MARCH 2024; ACCEPTED 12 MARCH 2024; text Contributions to Zoology 2024 2024-03-29 93 268 288 http://dx.doi.org/10.1163/18759866-bja10061 journal article 10.1163/18759866-BJA10061 1875-9866 12518921 Genus † Eogmelina gen. nov. Zoobank LSID urn:lsid:zoobank.org:act: 89D84 AB9-3C24-4B60-BE3C-D0B81C35FEA0 Zoobank publication LSID: urn:lsid:zoobank.org:pub: 18AD77A2-5812-4C84-B93C-8BB527A DEF38 Type species . † Eogmelina moldavica gen. et sp. nov. ( fig. 5 ) Other species . † Eogmelina prisca gen. et sp. nov. ( fig. 6 ) Diagnosis . Body tall and robust (up to 22 mm length) with or without dorsal pleonal projections, lateral pereonal projections absent, coxal plates I-III taller than wide, urosomites free and devoid of humps and tubercles. Antenna 1 peduncle short, not extending beyond the distal end of the 4th peduncular segment of antenna 2. The 3rd peduncular segment of antenna 2 is shorter than half the length of the 4th segment; 4th segment length subequal to head length. Propodi of gnathopods 1–2 similar in size and shape, rectangular, moderately developed, palm length subequal to posterior margin. Pereopods 3–7 robust and well developed, dactyli moderately developed and relatively straight. Pereopods 3–4 carpus longer than wide, not expanded. Length of pereopod 7 exceeds 0.4 of body length. Pereopod 7 basis taller than wide, posterior margin convex, without postero-distal lobe. Epimeral plates 2–3 with acute postero-inferior corners. Uropod 3 extends beyond the distal end of uropod 1, endopod/exopod ratio is 0.9. FIGURE 4 Morphological diversity of extant and fossil Ponto-Caspian gammaroids based on 43 morphometric measurements. (A) PCA plot depicting the morphospace occupation along the first two axes. Extant non-monotypic genera are shown with dimmed colors (dots or convex hulls if n> 2 species) while monotypic genera are shown with a gray square. Fossil taxa are shown with colored stars that are numbered according to species (see legend on lower left). Extreme morphologies are exemplified by drawings. (B) Biplot of variables along the first two PCA axes. C) A 3D PCA indicating morphospace occupation of fossils (colored triangles) and extant (gray dots) taxa within the first three axes. Differential diagnosis . Eogmelina gen. nov. can be readily distinguished from the fossil Ponto-Caspian genera Praegmelina and Andrussovia by the following characters: 1) combined length of antenna 2 peduncle segments 4 and 5 longer than head length (vs. shorter), 2) antenna 1 peduncle not reaching the distal end of the 4th peduncular segment of antenna 2 (vs. extending beyond it) (see key). Etymology . Derived from the Greek word eos (dawn), referring to its early appearance and plesiomorphic morphology, and the name of the extant genus Gmelina Sars, 1894 , to which it bares a superficial resemblance.