Demise of the dinosaurs led to super-sized mammals

The demise of the dinosaurs created the ecological opportunity for the diminutive prehistoric mammals of the time to become the largest creatures on Earth today, scientists have demonstrated conclusively for the first time.

A worldwide study of fossilised mammals has demonstrated beyond any doubt that it was the extinction of the dinosaur 65 million years ago that led to the explosive growth of the warm-blooded mammals.

Although it was long suspected this was the reason for the transition from dinosaur dominance to mammalian supremacy, a thorough investigation of fossil mammals dating back 140 million years has confirmed we would not have elephants today had it not been for the death of Argentinosaurus, one of the biggest-ever dinosaurs, and others like it.

The study found that, for the first 40 million years of their existence, mammals were mostly small, shrew-like creatures that lived in a narrow range of habitats. But, after the dinosaur disappeared, mammals evolved rapidly into much larger creatures, from leaf-eating giant sloths to tundra-munching mammoths.

"The dinosaur disappear and all of a sudden there is nobody else eating the vegetation. That's an open food source and mammals start going for it," said Jessica Theodor of the University of Calgary in Canada.

The study in the journal Science found many different types of mammals grew into gigantic forms. The biggest was a hornless rhinoceros-like herbivore that lived in Eurasia 34 million years ago called Indricotherium transouralicum, which weighed 17 tonnes and stood about 6m high at the shoulder.

- Independent