Search for: All records

The highest species richness and ecological diversity of extant snakes are in the tropics, primarily in South Asia and Central and South America. Tropical Africa has relatively lower richness and less diversity, but the evolution of tropical herpetofaunas, and the factors governing diversification through time at continental scales are poorly understood due to an understudied fossil record. The ecologies and geographic distributions of aniliid and uropeltoid snakes are examples. Modern species constitute either a grade or clade of fossorial, primarily wet forest taxa from South America and South Asia. Their distributions have historically been interpreted as Gondwanan vicariance following the isolation of Africa in the Early Cretaceous, but a definitive fossil record for these snakes is depauperate. Field research in the early Miocene (approx. 19 Mya) Tinderet sequence of western Kenya has produced precloacal vertebrae of an aniliid snake from multiple localities. Specimens possess vertebral apomorphies shared with extant South American Anilius scytale, including the morphology of the neural spine and prezygapophyseal angle. Combined with additional fossils from the Eocene of North Africa and Middle Miocene of Kenya, the Tinderet records demonstrate an unambiguous past record of an extant neotropical snake lineage in Africa and falsify previous vicariance hypotheses. Recent stable isotopic and palynological studies of Neogene eastern African fossil localities have indicated heterogenous environments, including C4 grasses and wood- to scrubland, associated with vertebrate faunas. Comparing climate parameters of habitats for extant Anilius and uropeltoid snakes as ecological analogues to the Tinderet snake with modern ecosystems equivalent to those reconstructed for the eastern African early Miocene demonstrates only limited overlap in precipitation and temperature values. This discord indicates either greater environmental heterogeneity than reconstructed for the early Miocene of eastern Africa, or a greater range of habitat variability in aniliid snakes than observed in extant Anilius. 

The first fossil apes published from Africa were discovered in the 1920s at the Tinderet site of Koru, Kenya. Since that time, the entire Tinderet fossil complex has produced thousands of fossil mammals, reptiles, and plants, including some of the most important early ape and stem catarrhine specimens. Here, we report results from geological, paleoecological, and paleontological surveys and samples conducted by our team between 2013-2023. A major part of our work has been to rediscover old but sometimes poorly documented fossil sites and to assess their potential for future research. One such site, Tonde Bridge, was thought to have no remaining fossil deposits but we report here the discovery of many new specimens. We have also discovered new fossil sites that may sample poorly known depositional and/or ecological settings. Our stratigraphic and geochronological results help to better ordinate major fossil outcrops with respect to each other. We have also specifically targeted the smallest microfauna as well as understudied taxonomic groups such as reptiles and amphibians. This work combined with other paleoecological analyses confirm closed habitats at many of the Tinderet sites. One site in particular has benefitted from extensive multi-proxy paleoecological reconstruction, allowing us to place some fossil apes within a dense forested environment. Finally, the discovery of important new primate specimens helps clarify some of the anatomical variation represented in historic collections but also extends the taxonomic variation from Tinderet. In particular, the discovery of a large-bodied nyanzapithecine from Koru suggests that size variation in this clade may have been similar to that found in proconsulids. 

Abstract. Lake Victoria, which is bordered by Uganda, Tanzania, Kenya, and has a catchment that extends to Rwanda and Burundi, is home to the largest human population surrounding any lake in the world and provides critical resources across eastern Africa. Lake Victoria is also the world's largest tropical lake by surface area, but it is relatively shallow and without a major inlet, making it very sensitive to changes in climate, and especially hydroclimate. Furthermore, its size creates abundant habitats for aquatic fauna, including the iconic hyper-diverse cichlids, and serves as a major geographic barrier to terrestrial fauna across equatorial Africa. Given Lake Victoria's importance to the eastern African region, its sensitivity to climate, and its influences on terrestrial and aquatic faunal evolution and dispersal, it is vital to understand the connection between the lake and regional climate and how the lake size, shape, and depth have changed through its depositional history. This information can only be ascertained by collecting a complete archive of Lake Victoria's sedimentary record. To evaluate the Lake Victoria basin as a potential drilling target, ∼ 50 scientists from 10 countries met in Dar es Salaam, Tanzania, in July 2022 for the International Continental Scientific Drilling Program (ICDP)-sponsored Lake Victoria Drilling Project (LVDP) workshop. Discussions of the main scientific objectives for a future drilling project included (1) recovering the Pleistocene and Holocene sedimentary records of Lake Victoria that document the dynamic nature of the lake, including multiple lacustrine and paleosol sequences; (2) establishing the chronology of recovered sediments, including using extensive tephra fingerprinting and other techniques from deposits in the region; (3) reconstructing past climate, environment, lacustrine conditions, and aquatic fauna, using an integrated multi-proxy approach, combined with climate and hydrologic modeling; and (4) connecting new records with existing sedimentary snapshots and fossils exposed in deposits around the lake, tying archaeological, paleontological, sedimentological, tectonic, and volcanic findings to new drilling results. The LVDP provides an innovative way to address critical geological, paleontological, climatological, and evolutionary biological questions about Quaternary to modern landscapes and ecosystems in eastern Africa. Importantly, this project affords an excellent opportunity to help develop conservation and management strategies for regional responses to current and future changes in climate, land use, fisheries, and resiliency of at-risk communities in equatorial Africa. 

The highest species richness and ecological diversity of extant squamates are in the tropics. Both their taxic richness and functional traits are predictably correlated to environmental factors, and the utility of these measures in the squamate fossil record is an emergent tool for paleoenvironmental reconstruction. Ongoing field research in the early Miocene (approx. 20–19 Mya) Tinderet sequence of western Kenya has produced a diverse record of squamates which provides environmental data for hominoid-bearing localities. The record consists of chamaeleonid, agamid, varanid, and amphisbaenid lizards as well as snake lineages including pythonids, colubroids, elapoids, and a newly discovered taxon sharing unique vertebral apomorphies with extant tropical South American Anilius scytale. Combined with additional fossils from the Eocene of North Africa, the new Tinderet taxon demonstrates an unambiguous past record of an extant neotropical snake lineage in Africa and falsifies previous vicariance hypotheses to explain the biogeographic histories of basal divisions within snakes. Recent stable isotopic and phytolith studies of Early to Middle Miocene eastern African fossil localities have indicated heterogenous environments, including C4 grasses and wood- to scrubland, associated with vertebrate faunas. The composition of squamate faunas is generally consistent with these reconstructions, with the new taxon providing precise evidence for precipitation. Comparing climate parameters of habitats for Anilius and other extant ecological analogues equivalent to those reconstructed for the eastern African Early Miocene indicates annual precipitation between 1500–2500 mm/year, consistent with wet tropical seasonal forests and rain forests. 

INTRODUCTION Inherent in traditional views of ape origins is the idea that, like living apes, early large-bodied apes lived in tropical forests. In response to constraints related to locomoting in forest canopies, it has been proposed that early apes evolved their quintessential upright torsos and acrobatic climbing and suspensory abilities, enhancing their locomotor versatility, to distribute their weight among small supports and thus reach ripe fruit in the terminal branches. This feeding and locomotor transition from a quadruped with a horizontal torso is thought to have occurred in the Middle Miocene due to an increasingly seasonal climate and feeding competition from evolving monkeys. Although ecological and behavioral comparisons among living apes and monkeys provide evidence for versions of terminal branch forest frugivory hypotheses, corroboration from the early ape fossil record has been lacking, as have detailed reconstructions of the habitats where the first apes evolved. RATIONALE The Early Miocene fossil site of Moroto II in Uganda provides a unique opportunity to test the predictions of terminal branch forest frugivory hypotheses. Moroto II documents the oldest [21 million years ago (Ma)] well-established paleontological record of ape teeth and postcranial bones from a single locality and preserves paleoecological proxies to reconstruct the environment. The following lines of evidence from Moroto II were analyzed: (i) the functional anatomy of femora and a vertebra attributed to the ape Morotopithecus ; (ii) dental traits, including molar shape and isotopic profiles of Morotopithecus enamel; (iii) isotopic dietary paleoecology of associated fossil mammals; (iv) biogeochemical signals from paleosols (ancient soils) that reflect local relative proportions of C 3 (trees and shrubs) and C 4 (tropical grasses and sedges that can endure water stress) vegetation as well as rainfall; and (v) assemblages of phytoliths, microscopic plant-derived silica bodies that reflect past plant communities. RESULTS A short, strong femur biomechanically favorable to vertical climbing and a vertebra indicating a dorsostable lower back confirm that ape fossils from Moroto II shared locomotor traits with living apes. Both Morotopithecus and a smaller ape from the site have elongated molars with well-developed crests for shearing leaves. Carbon isotopic signatures of the enamel of these apes and of other fossil mammals indicate that some mammals consistently fed on water-stressed C 3  plants, and possibly also C 4  vegetation, in a woodland setting. Carbon isotope values of pedogenic carbonates, paleosol organic matter, and plant waxes all point to substantial C 4 grass biomass on the landscape. Analysis of paleosols also indicates subhumid, strongly seasonal rainfall, and phytolith assemblages include forms from both arid-adapted C 4 grasses and forest-indicator plants. CONCLUSION The ancient co-occurrence of dental specializations for leaf eating, rather than ripe fruit consumption, along with ape-like locomotor abilities counters the predictions of the terminal branch forest frugivory hypotheses. The combined paleoecological evidence situates Morotopithecus in a woodland with a broken canopy and substantial grass understory including C 4 species. These findings call for a new paradigm for the evolutionary origins of early apes. We propose that seasonal, wooded environments may have exerted previously unrecognized selective pressures in the evolution of arboreal apes. For example, some apes may have needed to access leaves in the higher canopy in times of low fruit availability and to be adept at ascending and descending from trees that lacked a continuous canopy. Hominoid habitat comparisons. Shown are reconstructions of a traditionally conceived hominoid habitat ( A ) and the 21 Ma Moroto II, Uganda, habitat ( B ).