We describe a new species of gundi (Rodentia: Ctenodactylidae: Ctenodactylinae), Sayimys negevensis, on the basis of cheek teeth from the Early Miocene of the Rotem Basin, southern Israel. The Rotem ctenodactylid differs from all known ctenodactylid species, including Sayimys intermedius, which was first described from the Middle Miocene of Saudi Arabia. Instead, it most resembles Sayimys baskini from the Early Miocene of Pakistan in characters of the m1-2 (e.g., the mesoflexid shorter than the metaflexid, the obliquely orientated hypolophid, and the presence of a strong posterolabial ledge) and the upper molars (e.g., the paraflexus that is longer than the metaflexus). However, morphological (e.g., presence of a well-developed paraflexus on unworn upper molars) and dimensional (regarding, in particular, the DP4 and M1 or M2) differences between the Rotem gundi and Sayimys baskini distinguish them and testify to the novelty and endemicity of the former. In its dental morphology, Sayimys negevensis sp. nov. shows a combination of both the ultimate apparition of key-characters and incipient features that would be maintained and strengthened in latter ctenodactylines. Thus, it is a pivotal species that bridges the gap between an array of primitive ctenodactylines and the most derived, Early Miocene and later, gundis.

The Gray-faced Sengi (Rhynchocyon udzungwensis) is a newly-discovered species of sengi (elephant-shrew) and is the largest known extant representative of the order Macroscelidea. The discovery of R. udzungwensis provides an opportunity to investigate the scaling relationship between brain size and body size within Macroscelidea, and to compare this allometry among insectivorous species of Afrotheria and other eutherian insectivores. We performed a spin-echo magnetic resonance imaging (MRI) scan on a preserved adult specimen of R. udzungwensis using a 7-Tesla high-field MR imaging system. The brain was manually segmented and its volume was compiled into a dataset containing previously-published allometric data on 56 other species of insectivore-grade mammals including representatives of Afrotheria, Soricomorpha and Erinaceomorpha. Results of log-linear regression indicate that R. udzungwensis exhibits a brain size that is consistent with the allometric trend described by other members of its order. Inter-specific comparisons indicate that macroscelideans as a group have relatively large brains when compared with similarly-sized terrestrial mammals that also share a similar diet. This high degree of encephalization within sengis remains robust whether sengis are compared with closely-related insectivorous afrotheres, or with more-distantly-related insectivorous laurasiatheres.

The site of Loperot in West Turkana, Kenya, is usually assigned to the Early Miocene. Recent discoveries at Loperot, including catarrhine primates, led to a revision of its mammalian fauna. Our revision of the fauna at Loperot shows an unusual taxonomic composition of the catarrhine community as well as several other unique mammalian taxa. Loperot shares two non-cercopithecoid catarrhine taxa with Early Miocene sites near Lake Victoria, e.g., Songhor and the Hiwegi Formation of Rusinga Island, but Loperot shares a cercopithecoid, Noropithecus, with Buluk (Surgei Plateau, near Lake Chew Bahir). We use Simpson’s Faunal Resemblance Index (Simpson’s FRI), a cluster analysis, and two partial Mantel tests, to compare Loperot to 10 other localities in East Africa representing several time divisions within the Early and Middle Miocene. Simpson’s FRI of mammalian communities indicates that Loperot is most similar in its taxonomic composition to the Hiwegi Formation of Rusinga Island, suggesting a similarity in age (≥18 Ma) that implies that Loperot is geographically distant from its contemporaries, i.e., Hiwegi Formation of Rusinga Island, Koru, Songhor, and Napak, while at the same time older than other sites in West Turkana (Kalodirr and Moruorot). The cluster analysis of the similarity indices of all the localities separates Loperot from other Early Miocene sites in the study. Two partial Mantel tests show that both temporal distance and geographic distance between sites significantly influence similarity of the mammalian community among sites. Thus, Loperot’s unique location in space and time may explain why it has an unusual catarrhine community and a number of unique taxa not seen elsewhere.