Fossil rodents from Bone Cave at the Koanaka Hills locality, Botswana



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In this study I analyze a Middle Pleistocene rodent fauna from Bone Cave locality, Koanaka Hills, northwestern Botswana and attempt to reconstruct the paleoenvironment of the surrounding area. Only a few Pliocene and Pleistocene fossil localities exist between eastern and southern Africa, and the fossil rodents collected from within the Koanaka Hills partially fills this significant geographic and temporal gap in the paleontological record of Africa. Rodent remains from owl accumulations are frequently found in the fossil record and used to reconstruct the paleoenvironment Similarly, prey remains from owl accumulations are used to reconstruct modern community composition. Rodents are seen as particularly useful for reconstructing paleoenvironments over larger mammals as most genera commonly found at Pliocene and Pleistocene fossil localities in Africa are extant, which allows scientist to project modern environmental and habitat preferences to the past as a way to reconstruct past environments. However, there is no defined set of osteological apomorphies with which to identify some rodent taxa to an environmentally informative taxonomic level. This issue makes it difficult to accurately and systematically identify rodents from southern African fossil localities and reconstruct the paleoenvironment. To address this issue, a character matrix is created in this project of cranio-dental characters reported in resources and augmented with new characters derived from comparative images of museum specimens for representative rodent genera from southern Africa ≤ 5 kg. Results from the analysis of fossil specimens is the compared to trapping data of rodents in the area surrounding Koanaka Hills and two modern barn owl pellet assemblages from within the cave at Koanaka Hills allowing a unique opportunity to compare the fossil assemblage with the modern community in a known environment. One-hundred ninety-six fossil maxillary rodent specimens were identified to the genus and subfamily taxonomic level. Some rodent and nonmammalian fossil specimens identified suggest the environment around Bone Cave was similar to todays, but at some point during the Middle Pleistocene, there was a nearby source of water and wooded vegetation due to the presence of taxon such as Pelomys. While the presence of Pelomys, buttonquail, and amphibians in the fossil record of Bone Cave allows for the possibility of a more mesic past, they are not convincing by themselves. Pelomys and buttonquail are each represented by a single specimen, and amphibians occur at the Koanaka Hills today. The overwhelming majority of fossils found in the Bone Cave deposit represent taxa still found there today. Given these data, the most parsimonious interpretation is one of no change.



Rodents, Bone Cave, Koanaka Hills, Botswana, Middle Pleistocene, Micromammals