discovery In Chubut You’ve just changed one of the most persistent debates in paleontology: Did the polyphyle — an ancient lineage of mammals — really live in South America? The answer came in the form of A Small teethBut revealing.
Argentine researchers described Notopolytheles JoelisIt is a new species from the Upper Cretaceous period, of which only known remains remain. Upper molarIt was discovered in the La Colonia Formation. The research, published in the journal Scientific Reports, confirms for the first time with unequivocal evidence that these mammals, known so far mainly from North American, European and Asian records, were also part of southern ecosystems.
A while ago 170 million yearsWhile dinosaurs dominated the Earth’s surface, a group of small mammals evolved with unique teeth, adapted to crushing seeds, insects, and hard vegetables. The multiple tubercles are characterized by their molar forms with multiple cusps and, in many cases, by A cutting tooth is called plagiolacoidis considered one of its main evolutionary markers.
Despite their enormous success, even surviving a mass extinction at the Cretaceous-Paleogene boundary, their presence in the Southern Hemisphere has always been a source of controversy. To date, isolated plagiolacoid teeth have only been found in South America, similar to those in this group but also those found in other extinct mammals, such as Gondwanatheria, which has prevented their conclusive identification.
The Notopolytheles joelis molar, which is only a few millimeters long, has three rows of perfectly aligned cusps, a distinctive feature It is impossible to attribute it to another lineage. This feature allowed us to confirm that it was a true multi-tuberous group and, therefore, that the group was indeed inhabiting Patagonia.
The work was carried out by Javier Guelfo and Francisco Guín (CONICET-Museo de La Plata) with Nahuel Vega (CNEA). The researchers highlighted that this tooth has Unusually long root There are marked differences in the height of its rows, indicating a shape not previously recorded among its relatives in the Northern Hemisphere.
This discovery revives the hypotheses of paleontologist Rosendo Pascual, a pioneer in the study of fossil mammals in South America. Pascual confirmed that the plagioalacoid teeth found in Patagonia belong to the polygeneae and not to the Gondwanantheria.
The new finding coincides with their expectations: If multiple lineages were present in the region, it stands to reason that they coexisted with Gondwanathrians — another lineage typical of the supercontinent Gondwana — without having to assume more complex parallel dental evolutions.
The presence of multiple tubercles in South America and Australia, as well as indirect evidence in Antarctica, suggests that these animals roamed the ancient Gondwana landscape without significant barriers, millions of years before continental separation and the opening of the Drake Passage definitively isolated this region.
This record has also been combined with other evidence of biogeographical connections, such as the presence of fossil fossils in Patagonia and the path that marsupials would have followed from South America to Australia during the Paleogene.
The molar Notopolytheles joelis confirms that the diversity of mammals in Cretaceous Patagon was greater than previously thought. In a world dominated by dinosaurs, these small animals flourished and diversified, leaving a sparse but extremely important fossil record.
Each new part, no matter how small, allows us to complete the plot of the past, which still has huge gaps. This time, a young age was enough to rewrite an entire chapter of evolution.