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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.
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Consequences of Proposed Shoreline Deformation Scenarios for Jezero Crater, Mars
Abstract One of the most interesting questions about the climate and hydrology of early Mars is whether oceans existed and, if so, when. Various geologic features have been interpreted as ancient shorelines, but these features do not follow gravitational equipotentials. Prior work has shown that the elevation of the Arabia level, hypothesized to represent a large, early ocean, better conforms to an equipotential when correcting for global topographic change after its formation. Although the shoreline coordinates underlying these studies are debated, exploring the consequences of these topographic corrections allows additional observable consequences to be identified. Here we show that the topographic corrections cause Jezero crater, the landing site of the Perseverance rover, to be submerged under the proposed Arabia ocean. This precludes the ocean’s existence during known fluvio-lacustrine activity at Jezero and suggests the ocean did not exist during the main era of valley network formation in the Noachian/Early Hesperian. We identify a period of ∼10 8 yr years before fluvial activity at Jezero when the ocean could have existed and discuss potential observable consequences.
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- Award ID(s):
- 1847120
- PAR ID:
- 10328479
- Date Published:
- Journal Name:
- The Planetary Science Journal
- Volume:
- 2
- Issue:
- 4
- ISSN:
- 2632-3338
- Page Range / eLocation ID:
- 128
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3847/PSJ/ac01de
