A number of localities in Transylvania (Romania) have yielded vertebrate microfossil remains. Two localities have been stratigraphically and biochronologically dated to the late Eocene: i.e., Treznea and Bociu. The remaining three localities are dated to the early Oligocene: Mera, Cetățuie, and Suceag. The study of cricetid rodents corroborates the presence of this family in Eastern Europe during the late Eocene, as evidenced by the species Witenia sp., Bustrania cf. B. dissimile , and Eocricetodon cf. Eo. meridionalis. The cricetids identified in the sites of the early Oligocene age show a complete turnover and a notable increase in species richness following the Eocene/Oligocene boundary, with: Eucricetodon aff. Eu. huerzeleri, Tenuicricetodon arcemis gen. et sp. nov., Pseudocricetodon cf. Ps. montalbanensis, Paracricetodon cf. Pa. walgeri, Paracricetodon kavakderensis, Paracricetodon aff. Pa. stojonovici, and Paracricetodon wentgesi. In the context of the wider biogeographic history of Europe, these new discoveries indicate that Cricetidae arrived in Europe during at least two successive migrations from Asia in the late Eocene and earliest Oligocene. These migrations may have occurred via two different migration pathways through the north and south of Europe. In a second phase, Cricetidae arriving by the northern passway spread throughout Europe, whereas Cricetidae that arrived by the southern passway remained restricted to the central and southeastern Europe. The observations made on the Cricetidae allow for the proposal of a new, more general, scenario for the Eocene–Oligocene transition on a European scale, which is more complex than the “Grande Coupure” sensu stricto as initially proposed by Stehlin in 1909.
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Icaphoca choristodon n. gen., n. sp., described in the present study, represents the sixth monachine seal from the Neogene Pisco Formation of Peru. The species is solely known from the holotype, including a cranium with both mandibles, as well as five cervical vertebrae including the atlas and axis. This holotype was collected at the Cerro La Bruja locality, the type locality of Magophoca brevirostris, in the Ica Desert after which Icaphoca has been named. Stratigraphically, the holotype was recovered from strata underlying those of the Cerro La Bruja level (CLB level), from which Magophoca was recovered. These beds likely correspond with the P1-2 unit of the P1 sequence within the Pisco Formation. Assumed to be as old as 9 Ma (middle Tortonian), Icaphoca may be the oldest described monachine seal from the southeast Pacific. Following Magophoca and Noriphoca, Icaphoca is the third extinct monachine seal known to have six upper incisors. This plesiomorphic character is absent in all other extant and extinct Monachinae which have only four upper incisors. The elongation of the snout, as well as the presence of profound diastemas between the postcanine teeth, suggests that Icaphoca is closely related to Acrophoca from the upper Tortonian and Messinian of the Pisco Formation in the Sacaco area (Arequipa Department), c. 200 km southeast to Cerro La Bruja. The specific name choristodon refers to this spacing between the post-canine teeth. The close phylogenetic relationship between Icaphoca and Acrophoca is confirmed by the phylogenetic analysis, which retrieves both genera as sister taxa.
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