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| Pebanista yacuruna Benites-Palomino, Aguirre-Fernández, Baby, Ochoa, Altamirano, Flynn, Sánchez-Villagra, Tejada, de Muizon & Salas-Gismondi, 2024 Illustration: Jaime Bran twitter.com/BranArtworks |
Abstract
Several dolphin lineages have independently invaded freshwater systems. Among these, the evolution of the South Asian river dolphin Platanista and its relatives (Platanistidae) remains virtually unknown as fossils are scarce. Here, we describe Pebanista yacuruna gen. et sp. nov., a dolphin from the Miocene proto-Amazonia of Peru, recovered in phylogenies as the closest relative of Platanista. Morphological characters such as an elongated rostrum and large supraorbital crests, along with ecological interpretations, indicate that this odontocete was fully adapted to fresh waters. Pebanista constitutes the largest freshwater odontocete known, with an estimated body length of 3 meters, highlighting the ample resource availability and biotic diversity in the region, during the Early to Middle Miocene. The finding of Pebanista in proto-Amazonian layers attests that platanistids ventured into freshwater ecosystems not only in South Asia but also in South America, before the modern Amazon River dolphin, during a crucial moment for the Amazonian evolution.
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| Biogeographical and paleobiogeographic distribution of Iniidae and Platanistidae through the Neogene. Schematic representation of the region highlighting the presence of epicontinental waters in South America (pale blue). Extant geographical ranges of the Amazon river dolphin Inia and the South Asian river dolphins Platanista (A). Distribution of fossil Iniidae/Platanistidae records in the Early to Middle Miocene Pebas System (B) and Late Miocene Acre System (C). Modified from Benites-Palomino et al. (2021). |
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| Size comparison between “river dolphins” White silhouettes indicate the minimum body length calculated or recorded; gray body outlines indicate the largest size recorded or estimated in: Pontoporia blainvillei (C), Pebanista yacuruna† gen. et sp. nov. (D), Inia geoffrensis (E), Platanista gangetica (F), and Lipotex vexillifer (G). |
Systematic paleontology
Odontoceti
Platanistidae
Pebanista yacuruna sp. nov.
Etymology: The generic name Pebanista stresses the relationship between this taxon from the Pebas Fm. (section S1) and the extant Ganges and Indus river dolphins Platanista (Platanista gangetica and Platanista minor). The specific Kichua (northern Quechua) name honors the “yacuruna,” a mythical water creature in the Peruvian Amazonia.
Diagnosis and remarks:
The holotype skull of Pebanista yacuruna, MUSM 4017, has a preserved condylobasal length of 698 mm and an estimated bizygomatic width of 281 mm. The sutures between the cranial bones (e.g., maxilla-premaxilla suture along the rostrum) are well closed or fused, indicating an adult stage. Pebanista is recognized as a member of Platanistidae by having the vertex of the skull deviated leftwards (Fig. 2, A and B); asymmetry of the premaxillae in the rostrum and facial areas of the skull; braincase anteroposteriorly shorter than wide; and lack of contact of the palatines, with both projecting dorsolaterally (figs. S3 and S4). The rostrum of the holotype specimen is dorsoventrally flattened and elongated, a condition shared with the extinct Pomatodelphis, Prepomatodelphis, and Zarhachis, in contrast to the transversely compressed rostrum of extant Platanista. On the preserved portion, the rostrum is formed by the premaxillae, maxillae, and ...
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| Artistic reconstruction of Pebanista yacuruna gen. et sp. nov. by Jaime Bran. |
Aldo Benites-Palomino, Gabriel Aguirre-Fernández, Patrice Baby, Diana Ochoa, Ali Altamirano, John J. Flynn, Marcelo R. Sánchez-Villagra, Julia V. Tejada, Christian de Muizon and Rodolfo Salas-Gismondi. 2024. The Largest Freshwater Odontocete: A South Asian River Dolphin relative from the proto-Amazonia. SCIENCE ADVANCES. 10(12); DOI: 10.1126/sciadv.adk6320
