2023-07-21 04:00:03
An international team of paleontologists and geologists (France, Brazil and Argentina), notably mobilizing researchers and doctoral students from the Institute of Evolutionary Sciences in Montpellier, recounts the discovery in the depths of the Brazilian Amazon (The Amazon is a region of South America. It is a vast plain crossed by…) of a tiny primate (Primates (from the Latin primas, atis meaning “the one who occupies the first…) which upsets the origins of the New World monkeys ( The New World is a term designating the American continent as well as Oceania, etc. Revealed by a single fossil tooth (a fossil (derived from the noun of the Latin verb fodere: fossil, literally…), this species continent separated, to the west, from Asia and…) from the South more than 35 million years ago (Ma), from Africa (with an area of ​​30,221,532 km2 including the islands,…). A disconcerting detail however, this new primate is indeed a close relative of primitive forms… but from South Asia.
Rio Juruá, Acre (Brazilian Amazon). View from the bivouac location for the night of 08/30/2022. (© L. Marivaux)
Like the caviomorph rodents (guinea pigs, capybaras, chinchillas, etc.), South American or platyrrhine monkeys (capuchins, marmosets, penguins, sakis, squirrel, spider and howler monkeys) are among the most diverse mammals of the Neotropics today. Reconstructing the origins, geographic history, and early evolutionary stages of these mammals is one of the most compelling and challenging questions in paleobiology. In the fossil record of South America, these two groups appear suddenly in the middle of the Cenozoic (40-30 Ma), consensually from African ancestors.
Recent fossil discoveries in the Peruvian Amazon have revealed that two distinct groups of anthropoid primates of African origin colonized South America. A paleontological expedition, carried out on the Rio Juruá in western Amazonia (Brazil), led to the discovery of a very surprising new small fossil primate: Ashaninkacebus simpsoni. Its name is both a dedication to the native Asháninka communities living in the region and to the famous evolutionary paleontologist, George G. Simpson, a pioneer in the 1950s of paleontological research on the Rio Juruá.
The single tooth of Ashaninkacebus simpsoni (upper molar). Note the tiny size of this perfectly preserved fossil specimen, resting on the paleontologist’s index finger. (© NS Stutz).
This tiny Ashaninkacebus upsets the origin of the New World monkeys (The word world can designate:) because its analysis suggests that a third group of anthropoids would have participated in the colonization of South America by non-human primates. Indeed, and this is even more surprising, the teeth of this new primate are much closer morphologically to those of the primitive forms of South Asia, the Eosimiidae, than to those of the African primates usually considered. It must be said that the present analysis, by reconsidering the status of certain enigmatic forms from Africa, demonstrates that eosimiids were also present in Africa 40 Ma ago. ers!). The data indicate that Ashaninkacebus was very small in size (~230 g), close to that of today’s small marmosets, and that it fed mainly on insects (Insectes is a French-language journal of ecology and entomology intended for a wide audience…) and perhaps fruits. These characteristics obviously increased the chances of survival of its close ancestors on a natural floating island (mega-raft) during the extraordinary crossing of the Atlantic to South America from Africa some 40 million years ago. Finally, time estimates (Time is a concept developed by humans to understand the…) of divergence between species from the Old and New Worlds point to the potential role of intense meteorological phenomena associated with warming and occurring at the same time in West Africa, which would have favored the formation of these floating islands (shreds of land (Earth is the third planet in the Solar System in order of distance…) and plants detached from the margins of large rivers during intense floods).
The tooth of Ashaninkacebus simpsoni (upper molar). (© AM Ribeiro/L. Kerber).
Primates and rodents, arrived in South America by chance, are today among the most diversified mammals of the continent (The word continent comes from the Latin continere to “hold together”, or continens…). This diversity is the result of millions of years of on-site evolution. Like their fossil predecessors, modern monkeys and rodents thrive in the vast rainforests of the Amazon. The latter undergo a more marked splitting each day, under the effect of anthropogenic pressure. Knowing more about the long history of these mammals shows to what extent (Graphie) the extraordinary ecosystems that shelter them are vulnerable.
Reference
Marivaux, L., Negri, FR, Antoine, P.-O., Stutz, N., Condamine, FL, Kerber, L., Pujos, F., Ventura Santos, R., Alvim, AMV, Hsiou, AS, Bissaro JĂşnior, MC, Adami-Rodrigues, K. & Ribeiro, AM (2023).
An eosimiid primate of South Asian affinities in the Paleogene of Western Amazonia and the origin of New World monkeys. PNAS.
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#increasingly #confusing #origin #World #monkeys