London: Mammals, including humans, diversified on Earth in great numbers after the dinosaurs went extinction, researchers, including an Indian-origin scientist, report.

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According to the team from University College London, fossil records show that placental mammals, the group that today includes nearly 5,000 species including humans, became more varied in anatomy during the Paleocene epoch - the 10 million years immediately following the dinosaur event.

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.

They clearly took advantage of that opportunity, as we can see by their rapid increases in body size and ecological diversity.

"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,” explained senior author Dr Anjali Goswami.

The team studied the early evolution of placental mammals, the group including elephants, sloths, cats, dolphins and humans.

The scientists gained a deeper understanding of how the diversity of the mammals that roamed the Earth before and after the dinosaur extinction changed as a result of that event.

The mass extinction that wiped out the dinosaurs 66 million years ago is traditionally acknowledged as the start of the 'Age of Mammals' because several types of mammal appear for the first time immediately afterwards.

"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,” added Dr Thomas Halliday.

The team studied the bones and teeth of 904 placental fossils to measure the anatomical differences between species.

"Extinctions are obviously terrible for the groups that go extinct, non-avian dinosaurs in this case, but they can create great opportunities for the species that survive, such as placental mammals, and the descendants of dinosaurs: birds,” informed Dr Goswami.

The research was published in the Biological Journal of the Linnean Society.