Although mammalian domination of Earth occurred immediately following the dinosaurs’ demise, the new research shows it took 10 million to 15 million more years for the ancestors of modern-day mammals to appear.
“The common perception is that the mammals rose to their current status after the dinosaurs went extinct. While it is true that there is an increase in mammal diversity after this time … it is not in the mammals we see around us today,” said Olaf Bininda-Edmonds, an evolutionary biologist who led the study.
Mammals that flourished during that time were small, such as the cat-sized, rodent-like Ptilodus and the dog-sized meat eaters called Creodonts, but this burst of new species led to mostly evolutionary dead-ends.
Species that evolve after a mass extinction are usually short-lived, paleontologist Michael Benton told Nature.
The study shows that while there may have been some major groups of modern-day mammal ancestors present during this period of rapid evolution, the diversification of species that produced most current mammal groups did not occur until around 50 million years ago.
Using a new model of the evolutionary tree, which combined DNA data of the approximately 4,500 mammal species with fossils of extinct animals, researchers discovered this new era of development in mammal history.
“I was flabbergasted,” study co-author Ross MacPhee, curator of vertebrate zoology at the American Museum of Natural History in New York, told the Associated Press.
The ancestors of present-day mammals first appeared on Earth approximately 125 million years ago and showed an initial burst in diversity between 100 million and 85 million years ago, according to the report.