New Ostracod Genera Bathoniella (Bathonian and Lower Callovian of the East European Platform and Northern Germany) and Parabathoniella (Lower and Middle Bathonian of Scotland). Part 2: Evolution and Biostratigraphy

The results of comparative morphological and ontogenetic analyses of the ostracods Bathoniella Tesakova (East European Platform (EEP) and Northern Germany, Bathonian–lower Callovian) and Parabathoniella Tesakova (Scotland, lower–middle Bathonian) suggested their origin from representatives of the genus Glyptocythere Brand et Malz with reticulate ornamentation (Europe, Bajocian–Bathonian). The West European Parabathoniella evolved from G. comes Br. et Malz, while East European Bathoniella evolved from G. tuberosa (Khabarova). Both ancestral taxa evolved from the West European G. concentrica Br. et Malz, which migrated to the EEP with formation of the allopatric G. tuberosa in the late Bajocian. A replacement name G. pseudotuberosa Tesakova, nom. nov. is proposed for G. tuberosa Br. et Malz, 1962 from the lower Bathonian of Germany, a junior homonym. The development of ornamentation and linear dimensions in the lineage of reticulate Glyptocythere demonstrates a complete cycle of morphogenesis with paedomorphosis and magnification in Bajocian species and subsequent gerontomorphosis and minification in Bathonian representatives and their descendants Bathoniella in the Bathonian and early Callovian. The stratigraphic continuity of successive species made it possible to recognize new lineage zones in the EEP: G. tuberosa in the terminal upper Bajocian–lower Bathonian (Michalskii–Besnosovi zones), B. prima in the terminal lower Bathonian–upper Bathonian (Ishmae Zone–lower part of the Calyx/Infimum Zone), B. milanovskyi in the upper Bathonian (presumably the upper part of the Calyx/Infimum Zone)–lower Callovian (Elatmae Zone), B. paenultima in the lower Callovian (Subpatruus Zone, C. surensis, C. subpatruus, C. uzhovkensis biohorizons) and B. ultima in the lower Callovian (Subpatruus Zone, Ch. saratovensis Biohorizon–Calloviense Zone). Additionally, the B. milanovskyi Zone is recognized in Northern Germany. The species Parabathoniella elongata (Wakefield) from the lower and middle Bathonian of Scotland appears to have been the only member of the West European genus. Its homologous acquisition of bathoniellid sexual dimorphism at the same time as B. prima Tesakova allows a pan-European correlative level based on the first appearance of these species in the geological record to be drawn.