†Kenyaichthyidae fam. nov and †Kenyaichthys gen. nov - First Record of a Fossil Aplocheiloid Killifish (Teleostei, Cyprinodontiformes)

The extant Cyprinodontiformes (killifishes) with their two suborders Cyprinodontoidei and Aplocheiloidei represent a diverse and well-studied group of fishes. However, their fossil record is comparatively sparse and has so far yielded members of the Cyprinodontoidei only. Here we report on cyprinodontiform fossils from the upper Miocene Lukeino Formation in the Tugen Hills of the Central Rift Valley of Kenya, which represent the first fossil record of an aplocheiloid killifish. A total of 169 specimens - mostly extraordinarily well preserved and a sample of ten extant cyprinodontiform species were studied on the basis of morphometrics, meristics and osteology. A phylogenetic analysis using PAUP was also conducted for the fossils. Both the osteological data and the phylogenetic analysis provide strong evidence for the assignment of the fossils to the Aplocheiloidei, and justify the definition of the new family dagger Kenyaichthyidae, the new genus dagger Kenyaichthys and the new species dagger K. kipkechi sp. nov. The phylogenetic analysis unexpectedly places dagger Kenyaichthys gen. nov. in a sister relationship to the Rivulidae (a purely Neotropical group),a probable explanation might be lack of available synapomorphies for the Rivulidae, Nothobranchiidae and Aplocheilidae. The specimens of dagger K. kipkechi sp. nov. show several polymorphic characters and large overlap in meristic traits, which justifies their interpretation as a species flock in statu nascendi. Patterns of variation in neural and haemal spine dimensions in the caudal vertebrae of dagger Kenyaichthys gen. nov. and the extant species studied indicate that some previously suggested synapomorphies of the Cyprinodontoidei and Aplocheiloidei need to be revised

Five-fold expansion of the Caspian Sea in the late Pliocene: New and revised magnetostratigraphic and 40Ar/39Ar age constraints on the Akchagylian Stage

The Global climate reorganisation in the late Pliocene linked to enhancement of the Atlantic Ocean Thermohaline Circulation (AOTC), instigated a transition to glacial-interglacial cyclicity in the Quaternary. Enhancement of the AOTC amplified atmospheric precipitation over the Eurasian interior strengthening Northern Hemisphere Glaciation. Increased rainfall on the vast Russian Plain drained into the endorheic Caspian Sea, which makes the Caspian geological record highly potential for tracing atmospheric precipitation changes. Two major palaeohydrological events in the Caspian Sea, the Akchagylian transgression and the Akchagylian marine incursion, led to a five-fold enlargement of the Caspian Sea surface area and transformed the basin palaeoecology, enabling active interregional faunal dispersals. The Akchagylian Stage still lacks an unequivocal age model with two age constraints – the “long Akchagylian” (3.6–1.8 Ma) and the “short Akchagylian” (2.7–2.1 Ma) standing on magnetostratigraphic studies of geological records in Turkmenistan and the Kura Basin, respectively. The age discrepancies also exist within the Kura Basin, where the fossil mammal-bearing Kvabebi locality with Akchagylian marine fauna was magnetostratigraphically dated at 3.2 Ma. In this paper, we try to resolve the age contradictions for the Akchagylian Stage. We revisit the Kvabebi (Georgia) and Kushkuna (Azerbaijan) sections of the western Kura Basin and provide new magnetostratigraphic and 40Ar/39Ar age constraints on these marginal Akchagylian deposits. Moreover, we revise the magnetostratigraphy of 25 geological records from Turkmenistan and the Kura Basin and propose a new unified age model for the Akchagylian Stage: 1. Intrabasinal Akchagylian freshwater-mesohaline transgression at 2.95 ± 0.02 Ma; 2. Akchagylian marine incursion through establishment of a Caspian-Arctic connection (2.75–2.45 Ma); 3. Akchagylian–Apsheronian boundary highlighting a Caspian-Black Sea connection at 2.13 Ma. The sudden expansion of the Caspian Sea at 2.95 ± 0.02 Ma potentially correlates to the interglacial intensification of the AOTC between 2.95 and 2.82 Ma. The new ages constrain a much shorter (2.95–2.1 Ma) Akchagylian than in previously mentioned regional geological time scales (3.6–1.8 Ma) and strongly appeal to reconsider the ages of numerous archaeological and mammalian sites in the Caspian region

Five-fold expansion of the Caspian Sea in the late Pliocene: New and revised magnetostratigraphic and 40Ar/39Ar age constraints on the Akchagylian Stage

The Global climate reorganisation in the late Pliocene linked to enhancement of the Atlantic Ocean Thermohaline Circulation (AOTC), instigated a transition to glacial-interglacial cyclicity in the Quaternary. Enhancement of the AOTC amplified atmospheric precipitation over the Eurasian interior strengthening Northern Hemisphere Glaciation. Increased rainfall on the vast Russian Plain drained into the endorheic Caspian Sea, which makes the Caspian geological record highly potential for tracing atmospheric precipitation changes. Two major palaeohydrological events in the Caspian Sea, the Akchagylian transgression and the Akchagylian marine incursion, led to a five-fold enlargement of the Caspian Sea surface area and transformed the basin palaeoecology, enabling active interregional faunal dispersals. The Akchagylian Stage still lacks an unequivocal age model with two age constraints – the “long Akchagylian” (3.6–1.8 Ma) and the “short Akchagylian” (2.7–2.1 Ma) standing on magnetostratigraphic studies of geological records in Turkmenistan and the Kura Basin, respectively. The age discrepancies also exist within the Kura Basin, where the fossil mammal-bearing Kvabebi locality with Akchagylian marine fauna was magnetostratigraphically dated at 3.2 Ma. In this paper, we try to resolve the age contradictions for the Akchagylian Stage. We revisit the Kvabebi (Georgia) and Kushkuna (Azerbaijan) sections of the western Kura Basin and provide new magnetostratigraphic and 40Ar/39Ar age constraints on these marginal Akchagylian deposits. Moreover, we revise the magnetostratigraphy of 25 geological records from Turkmenistan and the Kura Basin and propose a new unified age model for the Akchagylian Stage: 1. Intrabasinal Akchagylian freshwater-mesohaline transgression at 2.95 ± 0.02 Ma; 2. Akchagylian marine incursion through establishment of a Caspian-Arctic connection (2.75–2.45 Ma); 3. Akchagylian–Apsheronian boundary highlighting a Caspian-Black Sea connection at 2.13 Ma. The sudden expansion of the Caspian Sea at 2.95 ± 0.02 Ma potentially correlates to the interglacial intensification of the AOTC between 2.95 and 2.82 Ma. The new ages constrain a much shorter (2.95–2.1 Ma) Akchagylian than in previously mentioned regional geological time scales (3.6–1.8 Ma) and strongly appeal to reconsider the ages of numerous archaeological and mammalian sites in the Caspian region