Tag : Ancestors

Washington: In-depth research of the fossil record has shown a Cretaceous origin for placental mammals, which include humans, dogs, and bats, indicating they co-existed with dinosaurs for a short period before the dinosaurs became extinct. The catastrophic destruction triggered by the asteroid hitting the Earth resulted in the death of all non-avian dinosaurs in an event termed the Cretaceous-Paleogene (K-Pg) mass extinction. Debate has long raged among researchers over whether placental mammals were present alongside the dinosaurs before the mass extinction, or whether they only evolved after the dinosaurs were done away with. Fossils of placental mammals are only found in rocks younger than 66 million years old, which is when the asteroid hit Earth, suggesting that the group evolved after the mass extinction. However, molecular data has long suggested an older age for placental mammals. In a new paper published in the journal Current Biology, a team of palaeobiologists from the University of Bristol and the University of Fribourg used statistical analysis of the fossil record to determine that placental mammals originated before the mass extinction, meaning they co-existed with dinosaurs for a short time. However, it was only after the asteroid impact that modern lineages of placental mammals began to evolve, suggesting that they were better able to diversify once the dinosaurs were gone. The researchers collected extensive fossil data from placental mammal groups extending all the way back to the mass extinction 66 million years ago. Lead author Emily Carlisle of Bristol's School of Earth Sciences said: "We pulled together thousands of fossils of placental mammals and were able to see the patterns of origination and extinction of th ...