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bioRxiv · 10.64898/2026.09.27.754785

Acrean fish diversity back in time: Paleoichthyology of the Rio Acre fossil fauna in Brazil

Ballen, G. A.·Alencar, K.·Muniz, F.·Guilherme, E.·Aldrin, L.·Lomba, S.·Dias-Costa, L. R.·Hsiou, A. S.
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Abstract

Freshwater fishes are an important component of the Neogene fossil record of South America. They have been recorded in the Acre fossil fauna, with considerable taxonomic and ecological diversity. Novel findings from the Patos locality in Acre State have produced several specimens representing eleven taxa, including the first occurrences in the fossil record of the genera Agamyxis, Glanidium, and Trachycorystes. These taxa comprise two orders, Characiformes and Siluriformes, with four and seven taxa respectively. The taxa found in the Patos locality are representative of typical modern Amazonian assemblages found in the drainages of the region, thus suggesting substantial ecological conservatism. An updated list of the Rio Acre fossil fish fauna is consistent with previous findings in the literature regarding clustering structure in fossil assemblages during the Neogene of South America.

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Ballen, G. A., Alencar, K., Muniz, F., Guilherme, E., Aldrin, L., Lomba, S., Dias-Costa, L. R., Hsiou, A. S.. 2026-10-02. Acrean fish diversity back in time: Paleoichthyology of the Rio Acre fossil fauna in Brazil. https://doi.org/10.64898/2026.09.27.754785

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