Tuesday 28 February 2017

Demise of dinos led to bigger beasts

Steve Connor

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 some 65 million years ago that was the key trigger leading to the explosive growth of the warm-blooded mammals.

Although it was long suspected that 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 that 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 or so of their existence, the mammals were mostly small, shrew-like creatures that lived in a narrow range of habitats.

However, after the dinosaur disappeared, the mammals evolved relatively rapidly into much larger creatures capable of exploiting a wide variety of ecological niches, from leaf-eating giant sloths to tundra-munching mammoths.

"Basically, 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, and it's more efficient to be a herbivore when you're big," said Jessica Theodor of the University of Calgary in Canada. "You lose dinosaurs 65 million years ago, and within 25 million years the system is reset to a new maximum for the animals that are there in terms of body size. That's actually a pretty short time frame, geologically speaking. That's really rapid evolution," Professor Theodor said.

The study in the journal 'Science' found that many different types of mammals grew into gigantic forms on different continents. 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 18ft high -- four times the size of a modern elephant.Being big is an advantage in a habitat with a large land mass of lots of vegetation, although it can make species vulnerable to sudden extinction if the environment changes rapidly. (© Independent News Service)

Irish Independent

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