Abstract

We describe new macro- and microfossils recovered on a field expedition to the North Quarry of Poponguine, a locality in western Senegal that spans the Late Cretaceous through the Early Paleogene, albeit with a likely unconformity at the base of the Danian. Newly discovered macrovertebrates from the Maastrichtian Cap de Naze Formation include pycnodonts, dyrosaurids, and chelonians, the latter two the oldest and first Cretaceous representatives of these clades from Senegal. Screenwashing of this deposit revealed that the matrix also consists of abundant microscopic biological clasts comprising osteichthyan vertebrae, spines, and cranial fragments, shark dermal denticles, invertebrates, and numerous ovoid coprolites among other fragments. These microfossils document a much less conspicuous portion of the paleobiodiversity. We describe the stratigraphy of this new locality and incorporate it into a new correlated section that ties together three other Late Cretaceous–Early Paleogene fossiliferous localities of the Senegalese-Mauritanian Basin. The presence of fossiliferous Danian rocks, which are notably rare in West Africa, is elucidated in our section, which synthesizes prior geological and paleontological work around Poponguine and in the nearby coastal region of Ndayane. Primarily dated using the biostratigraphy of ostracods and foraminiferans, the correlated rock units include the Paki and the Cap de Naze Formations of the Late Cretaceous Diass Group and the Ndayane and the Poponguine Formations of the Paleocene Cap-Vert Group, deposits that capture ancient near shore marine environments. The localities described, although separated by only a few kilometers, exhibit dramatic differences in thickness across faulted blocks of the Diass Horst. Dyrosaurids, which are common fossils in nearshore marine outcrops of West Africa, have been hypothesized to be of African origin and to have dispersed to South America in the Late Cretaceous. This dyrosaurid specimen, although fragmentary, documents a western extreme in the geographic range of African dyrosaurids where the clade would have been well situated for broader trans-Atlantic dispersal.