Did these prehistoric monkeys really cross the ocean on a mega-raft?

About 120 million years ago, the breakup of a supercontinent called Gondwana opened up the Atlantic Ocean, separating Africa and South America by several thousand kilometres. The latter remained isolated for millions of years, during which a very specialized endemic fauna developed there. Then, only 3 million years ago, the formation of the Isthmus of Panama between North and South America ended the geographic isolation of the vast island-continent, and allowed the mass arrival of new organisms onto the South American continent.

sudden mysterious appearance

However, a strange puzzle continues to haunt paleontologists. Fossils indicate that Hystricognathus rodents (represented today by the capybara, guinea pig, or naked mole rat) and anthropoid primates (what we commonly call apes) existed in South America for about 40 million years. This poses a problem: these groups are showing up far, far away from the South American continent, long after it was isolated. How could small land animals have reached these isolated lands millions of years before anyone else? Several hypotheses have been put forward by the scientific community, and the most commonly accepted one postulates one or more crossings of the Atlantic Ocean from Africa on makeshift boats! These incredible sea dispersals on rafts of vegetation are at the root of many colonization of isolated lands by animals that would normally not have been able to reach them, especially mammals and reptiles that are unable to fly or swim long distances. .

For example, many taxa present in Madagascar may have landed there after traversing the Mozambique Channel by raft. But the distance separating Madagascar from the African continent is much less than the distance separating the African continent from South America. Does the discovery of a new fossil monkey close to Asian and non-African species in Brazil call into question the oceanic dispersal hypothesis from Africa? To the contrary, a study was published in the journal Proceedings of the National Academy of Science brings new elements!

An extraordinary discovery made under difficult circumstances

In densely forested areas with a humid climate, fossils are rarely found, especially because there is less digging! The researchers from the Institute of Evolutionary Sciences in Montpellier (ISAM), who have just described the new fossil, have been investigating the Peruvian and Brazilian Amazon for fifteen years, despite the difficulty of the terrain. The conditions there are not very favorable, the sites are difficult to reach, and especially unstable. “You never know what a site will look like from one year to the nextExplaining Futura Laurent Marivaux (ISAM), first author of the study, Deposits can disappear very quickly due to precipitation, we must collect as much sediment as possible and sift the material directly onto the ground »,

Sifting through these sediments, the team discovered an extraordinary fossil, a small primate upper molar. “When my Brazilian colleague showed me the tooth, I couldn’t believe my eyesLaurent Marivaux says, This morphology was familiar to me, but completely unexpected in South America.,

What does this wonderful relationship represent

And for good reason: The roughly 34-million-year-old tiny primate was named ashininkebus simpsonswhich weighed about 230 grams and appears to have eaten insects, possibly fruit Iosimidae, a family of Asian monkeys… Does this mean that primates made the crossing between Asia and South America? Probably not. Phylogenetic analysis based on tooth morphologya simpsons who demonstrated his kinship with Iosimidae It also suggests that another molar, this time discovered in Tunisia and dated to -39.5 million years old, would belong to the Asian family. this taxon baptized ammariaMay well indicate that some primates migrated from Asia, passing through North Africa, before ending their journey in South America after a tumultuous journey!