No abstract

The evolution of the present-day African savannah fauna has been substantially influenced by the dispersal of Eurasian ancestors into Africa. The ancestors evolved endemically, together with the autochthonous taxa, into extant Afrotropical clades during the last 5 million years. However, it is unclear why Eurasian ancestors moved into Africa. Here we use sedimentological observations and soluble salt geochemical analyses of samples from a sedimentary sequence in Western Iran to develop a 10-million-year long proxy record of Arabian climate. We identify transient periods of Arabian hyperaridity centred 8.75, 7.78, 7.50 and 6.25 million years ago, out-of-phase with Northern African aridity. We propose that this relationship promoted unidirectional mammalian dispersals into Africa. This was followed by a sustained hyperarid period between 5.6 and 3.3 million years ago which impeded dispersals and allowed African mammalian faunas to endemically diversify into present-day clades. After this, the mid-Piacenzian warmth enabled bi-directional fauna exchange between Africa and Eurasia, which continued during the Pleistocene.

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The Upper Cretaceous (early Cenomanian) Bahariya Formation of Egypt has an outstanding reputation for its wealth of vertebrate remains, including a variety of iconic dinosaurs, like the carnivorous Spinosaurus and Carcharodontosaurus, as well as the herbivorous Aegyptosaurus and Paralititan. Besides these dinosaur fossils, the Bahariya Formation yielded also a wealth of invertebrate and plant remains, but even today many aspects concerning the continental palaeoenvironments reflected in these deposits (including the occurrence of palaeo-wildfires) have not been studied in detail. So far six distinct macro-charcoal bearing levels could be identified within the type section of the Bahariya Formation at Gabal El Dist profile, one of the most prolific outcrops of this formation in terms of fossil occurrence located in the north of the Bahariya Oasis, Western Desert, Egypt. Most of the charcoal investigated by means of SEM originates from ferns, pointing to a considerable proportion of this plant group within the palaeo-ecosystems that experienced fires. Gymnosperms and (putative) angiosperms have less frequently been identified. The collected data present evidence that the landscapes at the northern shores of Gondwana repeatedly experienced palaeo-wildfires, adding extra proof to previous statements that the Late Cretaceous was a fiery world on a global scale.

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We present an updated time frame for the 30 m thick late Miocene sedimentary Trachilos section from the island of Crete that contains the potentially oldest hominin footprints. The section is characterized by normal magnetic polarity. New and published foraminifera biostratigraphy results suggest an age of the section within the Mediterranean biozone MMi13d, younger than ~ 6.4 Ma. Calcareous nannoplankton data from sediments exposed near Trachilos and belonging to the same sub-basin indicate deposition during calcareous nannofossil biozone CN9bB, between 6.023 and 6.727 Ma. By integrating the magneto- and biostratigraphic data we correlate the Trachilos section with normal polarity Chron C3An.1n, between 6.272 and 6.023 Ma. Using cyclostratigraphic data based on magnetic susceptibility, we constrain the Trachilos footprints age at ~ 6.05 Ma, roughly 0.35 Ma older than previously thought. Some uncertainty remains related to an inaccessible interval of ~ 8 m section and the possibility that the normal polarity might represent the slightly older Chron C3An.2n. Sediment accumulation rate and biostratigraphic arguments, however, stand against these points and favor a deposition during Chron C3An.1n.

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Palynological investigations of the mid-Cretaceous, delta-influenced Malha Formation and superjacent transgressive Galala Formation exposed at Gebel El Minshera, north Sinai, Egypt, have yielded a sparse but biostratigraphically useful record of spores, pollen, and rare dinoflagellate cysts. A representative of the pollen genus Tricolporites, recovered 18 m above the base of the Malha Formation, is post-Aptian in age. An interval comprising the upper Malha Formation and lower Galala Formation is dated as middle Albian/middle Cenomanian based on the occurrence of Elaterosporites klaszii at the base and Afropollis jardinus at the top. A palynoflora from the upper Malha Formation, which includes ephedroids as well as Elaterosporites, has affinities with the Albian-Cenomanian Elaterates Province. The presence of palynomorphs associated with active fluvio-deltaic settings supports a proximal deltaic environment for the deposition of the Malha Formation, with the superjacent Galala Formation representing a subsequent marine flooding of the delta. A distinctive monospecific assemblage of the dinoflagellate cyst Subtilisphaera senegalensis in the upper part (Cenomanian) of the Galala Formation reflects an ecologically stressed, marginal-marine environment. This assemblage constitutes the first record of the mid-Cretaceous Subtilisphaera ecozone in Egypt and indeed east of Morocco, and in deposits as young as Cenomanian. The Malha and lowermost Galala Formations are characterized by type III-VI kerogen, which is gas prone but having little potential to produce hydrocarbons. Spore-pollen color indicates thermal maturity at the transitional to over-mature level, which is anomalously high when compared with equivalent deposits in the region.