An article published in the journal “Science” reports a study of fossils found at the Corral Bluffs site in Colorado, USA, dating back to a period that spans about a million years after the mass extinction that wiped out dinosaurs and many others species. A team of researchers led by Tyler Lyson and Ian Miller of the Denver Museum of Nature and Science examined what turned out to be fossils of remarkable quality of many species of animals and plants, including pollens, from the period in which life forms recovered after the great extinction.
Paleontologists estimate that about 75% of the species existing at the time of the impact of a giant meteorite became extinct due to the devastation caused by wildfires and by ash and dust that filled the Earth’s atmosphere and obscured the world. The scarcity of fossils dating back to the period after the extinction makes it difficult to understand how the subsequent recovery took place, a common problem in the field of paleontology. The lucky discovery of what proved to be a scientific treasure at the Corral Bluffs site could offer precious information on the evolution of life forms that survived at the beginning of the Paleogene period.
The top image (Courtesy Frank Verock/HHMI Tangled Bank Studios via AP. All rights reserved) shows some mammal skulls discovered at the Corral Bluffs site. The bottom image (Courtesy Frank Verock/HHMI Tangled Bank Studios via AP. All rights reserved) shows some plant fossils discovered at the Corral Bluffs site.
The fossils discovered show that the largest mammals that survived the mass extinction weighed less than half a kilo, 100,000 years later the largest ones weighed around 6 kg and after 200,000 more years the largest ones weighed around 20 kg. That’s a remarkable recovery, which went hand in hand with that of other animals and plants, of which fossil pollens also help to reconstruct that history. Palms and later walnut trees spread and diversified. About 700,000 years after the mass extinction the fossils show the appearance of the first legumes and at that point the largest mammals weighed around 45 kg.
The extinction of non-avian dinosaurs left various ecological niches totally empty. For the surviving mammals it was an advantage because the ones who found enough food didn’t have to worry about possible predators. In the long run, the recovery of plants and the appearance of legumes allowed mammals to find more food leading to a remarkable growth in their size within a million years, a short time from an evolutionary point of view.
These are very interesting discoveries and at the Corral Bluffs site there might be more fossils important to understand what happened after the mass extinction that happened 66 million years ago. However, that’s a limited geographical area, so the history of that ecosystem can’t easily be extended to the rest of the world of that time. A comparison with other fossils from that period found in other areas is important to verify similarities and differences. Every new discovery related to that period offers information about what happens during a mass extinction and in the following period, important to understand catastrophic events and their consequences.
