Mammal Diversity Became More Diverse After Dinosaurs Went Extinct

Researchers have found that mammalian diversity became more widespread on Earth right after the dinosaurs went extinct, according to a study at the University College London. The researchers examined numerous fossils, which indicated that placental mammals - about 5,000 species including humans - became more diverse during the Paleocene period, 10 million years after the mass extinction of the dinosaurs.

"When dinosaurs went extinct, a lot of competitors and predators of mammals disappeared, meaning that a great deal of the pressure limiting what mammals could do ecologically was removed," Dr. Anjali Goswami, a senior author of the study, said in a news release. "Mammals evolved a greater variety of forms in the first few million years after the dinosaurs went extinct than in the previous 160 million years of mammal evolution under the rule of dinosaurs."

The dinosaur extinction event was followed by the early evolution of a variety of placental mammals that roamed the land masses. The mass extinction of the dinosaurs marked the 'Age of Mammals' where for the first time numerous mammalian species began to emerge.  

The researchers examined bone and teeth belonging to 904 placental fossils, where they measured the anatomical differences between species. This information allowed them to create a new tree of life for early placental mammals and also enabled them to determine how mammalian species changed and varied over time.

"When we look at the mammals that were present, we find a burst of evolution into new forms, followed by specialization that finally resulted in the groups of mammals we see today," said Dr. Thomas Halliday, coauthor of the study. "The earliest placental mammal fossils appear only a few hundred thousand years after the mass extinction, suggesting the event played a key role in diversification of the mammal group to which we belong."

Extinctions can be devastating, however, they also create opportunities for new and surviving species to evolve and disperse, which is the case for placental mammals, according to the researchers.

The findings of this study were published in the Biological Journal of the Linnean Society.

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