Perissodactyls were a diverse order of mammals in the Northern Hemisphere during the Paleogene, but very few species remain today. They first appear during the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma) on the three continents of the Northern Hemisphere. Because they lack modern diversity, the study of their evolutionary history remains difficult, relying almost exclusively on fossils. In addition, their origin and early diversification remain elusive since all main groups appear at the same time with several genera and are already diverse, contrary to other modern mammal orders. Here, we investigate the early evolution of perissodactyls by analyzing a new dataset focusing on early species to obtain a new expansive phylogeny. This new topology, in combination with new observations and comparisons demonstrates that several genera are synonymous, simplifying the evolutionary picture of early perissodactyls. We show that the number of genera was overestimated and should be significantly reevaluated. These results also highlight fast dispersals of two genera, Pliolophus and Cardiolophus, on the three Northern continents, reflecting that of other modern mammals. The phylogeny also supports a potential Indo-Pakistani origin of perissodactyls. In addition, this large-scale phylogeny shows that many species that were named as “Hyracotherium” in the past (or sometimes “Eohippus”, the “dawn-horse”) and considered as “horses”, are not actually closely related to horses (Hippomorpha), including Hyracotherium itself, but can be considered as basal perissodactyls.
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RBINS Staff Publications 2026 OA
Among the most outstanding Cenozoic marine Fossil-Lagerstätten worldwide, the Peruvian Pisco Formation is renowned for its exceptional preservation and abundance of fossil vertebrates, especially cetaceans. We present an updated overview and interpretation of taphonomic data gathered during fifteen field campaigns (2006-2019) on 890 fossil marine vertebrates from the Miocene strata of the Pisco Formation exposed in the Ica Desert. In order to assess the factors that led to the formation of such an exceptional Konzentrat- and Konservat-Lagerstätte, we made observations that range from the taxonomic distribution, articulation, completeness, disposition and orientation of skeletons, to the presence of bite marks, associations with shark teeth and macro-invertebrates, bone and soft tissue (i.e., baleen) preservation, and the formation of attendant carbonate concretions and sedimentary structures. We propose that the exceptional preservation and abundance of the Pisco Formation specimens cannot be ascribed to a single cause, but rather to the interplay of favorable palaeoenvironmental factors and suitable timing of mineralizing processes, such as: i) low concentration of dissolved oxygen at the seafloor; ii) the early onset of mineralization processes; iii) rapid burial of the carcasses; and iv) original biological richness in the southeastern Pacific. Our observations provide a comprehensive overview of the taphonomic characteristics of one of the most significant fossiliferous deposits of South America and lead to the elaboration of a complex scenario for the preservation of its marine vertebrates that might serve as a reference for explaining the formation of other marine vertebrate Fossil-Lagerstätten worldwide.
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RBINS Staff Publications 2021
