Kanapoi revisited: Paleoecological and biogeographical inferences from the fossil fish

Aridity, availability of drinking water and freshwater foods, and hominin and archeological sites during the Late Pliocene-Early Pleistocene in the western region of the Turkana Basin (Kenya): A review

Although the Turkana Basin is one of the driest regions of the East African Rift, its Plio-Pleistocene sediments are rich in freshwater vertebrates and invertebrates, providing evidence that freshwater resources were available to hominins in this region during the Plio-Pleistocene (4.2-0.7 Ma). Here we provide an overview of the hydroconnectivity of the Turkana Basin. We then review the period during which freshwater river and lake systems expanded into the western region of the Turkana Basin, where hominin and archeological sites have been discovered in sediments dating back to the Late Pliocene-Pleistocene. Freshwater conditions are reconstructed from river and lake sediments and the flora and micro- and macofauna they contain. Data synthesis suggests that drinking water and freshwater foods prevailed in the western region of the Turkana Basin at 4.20-3.98 Ma, 3.70-3.10 Ma, 2.53-2.22 Ma, then between 2.10 and 1.30 Ma and intermittently from 1.27 to 0.75 Ma. Milestones in hominin evolution occurred in this context, such as the first occurrence of Australopithecus anamensis (4.20-4.10 Ma) and Kenyanthropus platyops (3.50 Ma and 3.30-3.20 Ma), the presence of Paranthropus aethiopicus (2.53-2.45 Ma), early Homo (2.33 Ma), Paranthropus boisei (2.25 Ma and 1.77-1.72 Ma) and Homo ergaster/Homo erectus (1.75 Ma, 1.47-1.42 Ma and 1.10-0.90 Ma). Developments in hominin behavior also occurred during this timeframe, including the first known stone tools (3.30 Ma), the oldest Oldowan sites (2.34 Ma and 2.25 Ma) in the Turkana Basin, the earliest known evidence for the emergence of bifacial shaping in eastern Africa (1.80 Ma), and the first known Acheulean site (1.76 Ma). Our synthesis suggests that, diachronic variation in hydroconnectivity played a role on the amount of drinking water and freshwater foods available in the western region of the Turkana Basin, despite regional aridity.

Major shifts in biogeographic regions of freshwater fishes as evidence of the Anthropocene epoch

Animals and plants worldwide are structured in global biogeographic regions, which were shaped by major geologic forces during Earth history. Recently, humans have changed the course of events by multiplying global pathways of introduction for nonindigenous species and propagating local species extirpations. Here, we report on how introductions and extirpations have changed the distributions of freshwater fishes worldwide and how it affected their natural biogeographic regions. We found major shifts in natural regions, with the emergence of an intercontinental region arising from the fusion of multiple faunas, which we named Pan-Anthropocenian Global North and East Asia (PAGNEA). The PAGNEA region is evocative of the Pangea supercontinent, as flows of introductions show that dispersal has become possible again across multiple continents, suggesting that human activities have superseded natural geological forces. Our results constitute evidence on the expected modification of biostratigraphic boundaries based on freshwater fish, which are abundant in the fossil record, thereby supporting the concept of the Anthropocene epoch.

A lower Pliocene Erymnochelyini turtle (Pleurodira, Podocnemididae) from the Democratic Republic of Congo

The presence of a pleurodiran turtle putatively attributable to Erymnochelys madagascariensis (i.e., the only representative of Erymnochelyini that is part of the current biodiversity) or to a closely related form was recognized, in the early 1990s, for the Lower Pliocene record of the Sinda-Mohari region (Democratic Republic of Congo). The material attributable to it was restricted to postcranial remains. Although some elements of the anterior region of the skull were subsequently found, this taxon had not been analyzed in detail until now. Knowledge about Erymnochelyini has increased remarkably since the 1990s and, especially, during the 21st century. The taxon from the Democratic Republic of Congo is here analyzed in detail, not only considering current knowledge about the lineage but also incorporating new material into this study, highlighting several partial skulls. Thus, it corresponds to one of the members of this lineage represented by a greater number of skulls. It is attributed to a new taxon, Mokelemys mbembe gen. et sp. nov., being the only representative of Erymnochelyini currently known for the Pliocene record.

The environments of Australopithecus anamensis at Allia Bay, Kenya: A multiproxy analysis of early Pliocene Bovidae

Australopithecus anamensis, among the earliest fully bipedal hominin species, lived in eastern Africa around 4 Ma. Much of what is currently known about the paleoecology of A. anamensis comes from the type locality, Kanapoi, Kenya. Here, we extend knowledge of the range of environments occupied by A. anamensis by presenting the first multiproxy paleoecological analysis focusing on Bovidae excavated from another important locality where A. anamensis was recovered, locality 261-1 (ca. 3.97 Ma) at Allia Bay, East Turkana, Kenya. Paleoenvironments are reconstructed using astragalar ecomorphology, mesowear, hypsodonty index, and oxygen and carbon isotopes from dental enamel. We compare our results to those obtained from Kanapoi. Our results show that the bovid community composition is similar between the two fossil assemblages. Allia Bay and Kanapoi bovid astragalar ecomorphology spans the spectrum of modern morphologies indicative of grassland, woodland, and even forest-adapted forms. Dietary reconstructions based on stable isotopes, mesowear, and hypsodonty reveal that these bovids' diet encompassed the full C₃ to C₄ dietary spectrum and overlap in the two data sets. Our results allow us to confidently extend our reconstructions of the paleoenvironments of A. anamensis at Kanapoi to Allia Bay, where this pivotal hominin species is associated with heterogeneous settings including habitats with varying degrees of tree cover, including grasslands, bushlands, and woodlands.