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
This study focuses on species occupying the three strata of an Amazonian rainforest: the ground and leaf litter, the understorey and the canopy. We employed only two sampling techniques: Winkler extraction for ground-dwelling ants and direct observations for understorey and canopy species on large branches cut off by a climber. We identified 494 ant species from 10 subfamilies and 77 genera over approximately 3.0 ha (Chao1 = 607 species; 95% CI: 566-670 species). Although we found fewer arboreal ants compared to approaches using insecticide fogging, this study confirms similarities between the ant diversity in Amazonian and Mesoamerican rainforests. The functional traits of these ants (i.e., diet, nest-site preference, population size of the colony) allowed us to identify seven clusters. Cluster 1 is a "hodgepodge" grouping arboreal or ground-dwelling species with different-sized colonies (76 species). Cluster 2 primarily includes small colonies of ground-nesting generalist feeders (142 species). Cluster 3 comprises all arboreal species from the understorey inhabiting myrmecophyte domatia or palm trees plus arboreal species with medium-sized colonies (37 species). Cluster 4 includes all territorially dominant arboreal ants plus one ground-dwelling species (21 species). All fungus-growing species belong to Cluster 5, which also contains ground-nesting generalist feeders and generalist predators (148 species). All doryline army ants are grouped in Cluster 6 along with one ponerine known for its nomadic behavior (15 species). Almost all specialized predators belong to Cluster 7 (55 species); however, Cluster 5 includes two ponerine species that prey exclusively on termites. Based on a nonmetric multidimensional scaling (NMDS), we confirmed that the position of these clusters corresponded fairly well to the three forest strata. Thus, analyzing functional traits enables the trophic position of most ants and their place in the vertical strata of Neotropical rainforests to be determined.
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RBINS Staff Publications 2025
