Widespread loss of mammalian lineage and dietary diversity in the early Oligocene of Afro-Arabia

Dorien De Vries,Hesham M Sallam,Steven Heritage,Erik R Seiffert,Matthew R Borths

doi:10.1038/s42003-021-02707-9

Abstract

Diverse lines of geological and geochemical evidence indicate that the Eocene-Oligocene transition (EOT) marked the onset of a global cooling phase, rapid growth of the Antarctic ice sheet, and a worldwide drop in sea level. Paleontologists have established that shifts in mammalian community structure in Europe and Asia were broadly coincident with these events, but the potential impact of early Oligocene climate change on the mammalian communities of Afro-Arabia has long been unclear. Here we employ dated phylogenies of multiple endemic Afro-Arabian mammal clades (anomaluroid and hystricognath rodents, anthropoid and strepsirrhine primates, and carnivorous hyaenodonts) to investigate lineage diversification and loss since the early Eocene. These analyses provide evidence for widespread mammalian extinction in the early Oligocene of Afro-Arabia, with almost two-thirds of peak late Eocene diversity lost in these clades by ~30 Ma. Using homology-free dental topographic metrics, we further demonstrate that the loss of Afro-Arabian rodent and primate lineages was associated with a major reduction in molar occlusal topographic disparity, suggesting a correlated loss of dietary diversity. These results raise new questions about the relative importance of global versus local influences in shaping the evolutionary trajectories of Afro-Arabia’s endemic mammals during the Oligocene.

Highlights

Diverse lines of geological and geochemical evidence indicate that the Eocene-Oligocene transition (EOT) marked the onset of a global cooling phase, rapid growth of the Antarctic ice sheet, and a worldwide drop in sea level
The nature of the Eocene-Oligocene transition (EOT) on the Afro-Arabian landmass has long been enigmatic, but recent paleontological sampling has improved our understanding of this phase[12,13,14,15,16,17]; this enriched context has inspired proposals of increased geographic provincialism of mammalian communities in the early Oligocene of Africa[13], and led to the identification of multiple strepsirrhine primate extinctions in northern Africa near the EOB18
These four clades include a great diversity of living and extinct species that have lived in a wide range of arboreal and terrestrial habitats that could have been impacted by environmental change during the early Oligocene

Summary

Results and discussion

Prior to 15 Ma, Afro-Arabian hyaenodonts show the same LTT peaks as are seen in the composite tree of primates and rodents (latest Eocene and early Miocene), with a distinct mid-Oligocene diversity trough (Fig. 1d). When all of the ancestral states for primate and rodent DTMs are pooled, long-term shifts toward relatively high OPCR values and relatively low RFI and ariaDNE values are evident in the mid-Oligocene, following periods of increased variability for both metrics in the late Eocene (Fig. 3). Prior to the EOB, Afro-Arabian anthropoids show little movement of their dental topographic (DT) morphospace (total Eocene Euclidean path length of 0.59, Fig. 4a, b), whereas that of strepsirrhines shifts rather dramatically over the same interval (Eocene path length of 1.97) (Fig. 4a, b) This pattern suggests the possibility of competitive displacement of middle and late Eocene strepsirrhines by anthropoids within their shared arboreal habitats. The environmental context for these pulses of extinction and diversification will only be clarified through a dedicated effort to extract paleotemperature estimates, stable

15 Ma Strepsirrhini

Methods

Code availability