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Remingtonocetidae are Eocene archaeocetes that represent a unique experiment in cetacean evolution. They possess long narrow skulls, long necks, fused sacra, and robust hind limbs. Previously described remingtonocetids are known from middle Eocene Lutetian strata in Pakistan and India. Here we describe a new remingtonocetid, Rayanistes afer, n. gen. n. sp., recovered from a middle to late Lutetian interval of the Midawara Formation in Egypt. The holotype preserves a sacrum with four vertebral centra; several lumbar and caudal vertebrae; an innominate with a complete ilium, ischium, and acetabulum; and a nearly complete femur. The ilium and ischium of Rayanistes are bladelike, rising sharply from the body of the innominate anterior and posterior to the acetabulum, and the acetabular notch is narrow. These features are diagnostic of Remingtonocetidae, but their development also shows that Rayanistes had a specialized mode of locomotion. The expanded ischium is larger than that of any other archaeocete, supporting musculature for powerful retraction of the hind limbs during swimming. Posteriorly angled neural spines on lumbar vertebrae and other features indicate increased passive flexibility of the lumbus. Rayanistes probably used its enhanced lumbar flexibility to increase the length of the power stroke during pelvic paddling. Recovery of a remingtonocetid in Egypt broadens the distribution of Remingtonocetidae and shows that protocetids were not the only semiaquatic archaeocetes capable of dispersal across the southern Tethys Sea.

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A new specimen of Basilosaurus cetoides was discovered on the banks of the Flint River in Albany, Georgia, USA, in 2010. This fossil, which was the most complete specimen of the species from Georgia to date, consisted of five nearly complete and two partial post-thoracic vertebrae, tentatively identified as S4 through Ca6. During excavation, however, the site was looted and most of the specimen was lost to science. Nonetheless, we use this discovery as an opportunity to update the current state of knowledge on the stratigraphic, biogeographic, and environmental distribution of Basilosaurus in North America, as well as the position of the late Eocene shoreline in the southeastern United States. The results show that Basilosaurus was most abundant across the southeastern coastal plain during the early to middle Priabonian, coincident with the late Eocene maximum marine transgression. The decline in Basilosaurus localities is associated with the retreating shoreline of the terminal Eocene. The majority of Basilosaurus localities fall well south of the position of the late Eocene shoreline hypothesized in this study, suggesting the genus favored middle to outer neritic zones of the epicontinental sea. The comparatively low number of Priabonian specimens in the Atlantic Coastal Plain versus the Gulf Coastal Plain, then, suggests the presence of shallow zones in the Atlantic Coastal Plain that may have limited the distribution of Basilosaurus across the region. The hypothesized shoreline of this study ultimately differs from earlier reconstructions by extending the Mississippi embayment at the Bartonian/Priabonian boundary farther north than previously noted.

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