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We report on a nearly complete cranium of Ekweeconfractus amorui gen. et sp. nov. (Hyaenodonta, Teratodontinae), from the early Miocene of Moruorot, Kenya. The cranium is dorsoventrally compressed, but sufficiently intact to allow for digital reconstruction of the neurocranium, resulting in a digital endocast that gives us a first glimpse into teratodontine brain morphology. The virtual endocast is one of the most well preserved of any hyaenodont known to date, with many of the cranial nerves and blood vessels identifiable. Endocasts are known from only a handful of hyaenodont species and little work has been done on hyaenodont brains in recent decades. To better understand the evolution of the brain in these animals, we place the endocast of E. amorui gen. et sp. nov., as well as several other previously described endocasts, in the latest phylogenetic framework. This analysis suggests that the expansion of the neocortex occurred convergently in several clades of Hyaenodonta. Our study provides a basis for future research on brain evolution in Hyaenodonta.

The ecological preferences of ruminant artiodactyls are commonly used to reconstruct the paleoenvironment of Neogene fossil localities throughout Africa. However, comparatively little research has focused on the ecology of ruminant artiodactyls from the Miocene of Africa. Here, we contribute new molar mesowear and hypsodonty data for the ruminant artiodactyls from the early and middle Miocene of Kenya and Uganda. Macroscopic dental characteristics of 608 tragulids, stem pecorans, giraffoids, and bovids dated to between 20 and 13.7 Ma were analyzed. Our hypsodonty results reveal that, whereas tragulids remain brachydont throughout the early and middle Miocene, pecoran ruminants experience an increase in hypsodonty due to the appearance of high-crowned bovids and climacoceratids that migrate into eastern Africa in the middle Miocene. Results from dental mesowear analysis suggest that all tragulids and pecorans were likely browsers, with only one taxon showing mesowear values that overlap with both browsers and mixed feeders in both the upper and lower molars (Canthumeryx sirtensis). None of the taxa analyzed had mesowear scores indicative of a grazing diet. Surprisingly, middle Miocene bovids and climacoceratids, despite possessing gross tooth morphologies adapted to abrasive diets, were largely utilizing a browsing diet. Although the early and middle Miocene habitats of eastern Africa were likely very heterogenous, none of the ruminant artiodactyls present in these habitats is interpreted as having incorporated grasses into their diet in significant quantities.

Field expeditions to Bukwa in the late 1960s and early 1970s established that the site had a small but diverse early Miocene fauna, including the catarrhine primate Limnopithecus legetet. Initial potassium-argon radiometric dating indicated that Bukwa was 22 Ma, making it the oldest of the East African early Miocene fossil localities known at the time. In contrast, the fauna collected from Bukwa was similar to other fossil localities in the region that were several million years younger. This discrepancy was never resolved, and due to the paucity of primate remains at the site, little subsequent research took place. We have collected new fossils at Bukwa, reanalyzed the existing fossil collections, and provided new radiometric dating. 40Ar/39Ar incremental heating ages on lavas bracketing the site indicate that the Bukwa fossils were deposited ∼19 Ma, roughly 3 Ma younger than the original radiometric age. Our radiometric dating results are corroborated by a thorough reanalysis of the faunal assemblage. Bukwa shares taxa with both stratigraphically older localities (Tinderet, Napak) and with stratigraphically younger localities (Kisingiri, Turkana Basin) perfectly corresponding to our revised radiometric age. This revised age for Bukwa is important because it indicates that significant faunal turnover may have occurred in East Africa between 20 and 19 Ma. Bukwa samples immigrant taxa such as large suids, large ruminants, and ochotonids that are absent from stratigraphically older but well-sampled localities in the region, such as Tinderet (∼20 Ma) and Napak (20 Ma). Further age refinements for Bukwa and the entire East African early Miocene sequence will help to constrain the timing of this faunal turnover event, of particular importance in paleoanthropology since this temporal sequence also provides us with what is currently our best window into the early evolution of cercopithecoid and hominoid primates.

Renewed research at the early Miocene fossil site of Bukwa in northeastern Uganda has resulted in new fossil finds, including fish, with representatives of two families, Cichlidae and Alestidae. Although the two families were previously briefly reported from Bukwa, we here give a more detailed account of the fishes based on newly collected material. The cichlid material, mainly composed of vertebrae, can be tentatively assigned to one or more species of Pseudocrenilabrinae. The alestid material, comprising a diversity of teeth, likely represents several different species of Alestes, Brycinus, and/or Bryconaethiops. Although the ichthyofaunal diversity of Bukwa is low, the fishes are important for indicating the paleoenvironment and hydrographic connections of Bukwa. The early Miocene was a critical time for African faunas, because it was during this time that the Afro-Arabian and Eurasian plates came into contact with one another, ending the long isolation of Africa, which, along with rifting in E...

Early Miocene fossils from Rusinga Island, Kenya, provide some of the best evidence for catarrhine evolution and diversification, and, together with more than eighty-five other mammalian species, form an important comparative reference for understanding faunal succession in East Africa. While there is consensus over the stratigraphic position of most of Rusinga's volcaniclastic deposits, the lacustrine Kulu Formation has been placed in various parts of the geological sequence by different researchers. To resolve this discrepancy, we conducted detailed geological analyses which indicate that the Kulu Formation was formed in the Early Miocene during a period of volcanic inactivity and subsidence following the early, mainly explosive hyper-alkaline phase of the Kisingiri complex and prior to the final eruptions of nephelinitic lavas. The underlying Hiwegi and older formations were locally deformed and deeply eroded before sedimentation began in the Kulu basin, so that the Kulu sediments may be significantly younger than the 17.8 Ma Hiwegi Formation and not much older than the overlying Kiangata Agglomerata-Lunene Lava series, loosely dated to ca. 15 Ma. The overall similarities between Kulu and Hiwegi faunas imply long-term ecological stability in this region. Our stratigraphic interpretation suggests that the Kulu fauna is contemporaneous with faunas from West Turkana, implying that differences between these assemblages—particularly in the primate communities—reflect paleobiogeographic and/or paleocological differences. Finally, the position of the Kulu Formation restricts the time frame during which the substantial faunal turnover seen in the differences between the primate and mammalian communities of Rusinga and Maboko Islands could have occurred.

Limnopithecus is a small-bodied catarrhine genus that is widespread throughout early Miocene sites in East Africa. Although two species of this genus have been described – Limnopithecus legetet (type species) and Limnopithecus evansi – they are poorly known anatomically and their systematic positions remain unresolved. Here, we provide detailed descriptions and comparisons for two well-preserved maxillary specimens that we attribute to L. evansi. These specimens come from the type locality of the species, Songhor in western Kenya, and add greatly to our knowledge of its dentognathic morphology. Together, they preserve the entire unilateral upper dentition, with overlapping elements demonstrating conspecificity, and provide new information about I2 morphology and aspects of the palate, nasal aperture, and maxillary sinuses. Detailed morphological comparisons suggest that specimens referred to Limnopithecus from Songhor, Koru, and Rusinga share a unique I2 morphology not found in any other early Miocene catarrhine. This argues in favor of congeneric status for L. evansi and L. legetet. Moreover, features such as a broad palate, premolar morphology, and the relative proportions of the premolars of L. evansi distinguish it from Lomorupithecus harrisoni, another early Miocene catarrhine from Napak, Uganda. This finding challenges a recently proposed taxonomic interpretation that Lomorupithecus and L. evansi are conspecific. Our results underscore the distinctiveness of L. evansi and Lo. harrisoni, thereby reaffirming the validity of the taxon Lo. harrisoni and indicating that the Songhor and Napak catarrhine communities were relatively distinct, despite their apparent contemporaneity.

Kelba quadeemae , a fossil mammal from the Early Miocene of East Africa, was originally named on the basis of three isolated upper molars. Kelba has previously been interpreted as a creodont, a pantolestid, an insectivoran, and a hemigaline viverrid. The true affinities of this taxon have remained unclear because of the limited material and its unique morphology relative to other Miocene African mammals. New material of Kelba from several East African Miocene localities, most notably a skull from the Early Miocene locality of Songhor in Western Kenya, permits analysis of the affinities of Kelba and documents the lower dentition of this taxon. Morphological comparison of this new material clearly demonstrates that Kelba is a member of the order Ptolemaiida, a poorly understood group whose fossil record was previously restricted to the Oligocene Fayum deposits of northern Egypt. Phylogenetic analysis supports the monophyly of the Ptolemaiida, including Kelba , and recovers two monophyletic clades within the order. We provide new family names for these groups and an emended diagnosis for the order. The discovery of ptolemaiidans from the Miocene of East Africa is significant because it extends the known temporal range of the order by >10 million years and the geographic range by >3,200 km. Although the higher-level affinities of the Ptolemaiida remain obscure, their unique morphology and distribution through a larger area of Africa (and exclusively Africa) lend support to the idea that Ptolemaiida may have an ancient African origin.