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Dino diversity earlier than first thought

dinosaur skeleton

Dinosaur diversity was well established before the Cretaceous Terrestrial Revolution, say British researchers (Source: WikiMedia)

The belief that dinosaurs underwent explosive species diversification just before they were wiped out is an illusion, a study says.

The end of the Cretaceous era some 65 million years, marked the demise of the dinosaurs - possibly due to a space rock that slammed into earth.

A new study, published in the Proceedings of the Royal Society Proceedings B, suggests the evolution of dinosaurs leading up to this event took place over a period of millions of years.

Fossils dating from between 125 million to 80 million years ago, a period called the Cretaceous Terrestrial Revolution, suggest the earth experienced riotous biodiversity. This resulted in the evolution of flowering plants, social insects, butterflies, modern groups of lizards, mammals and possibly birds.

Some experts have suggested that dinosaurs were also part of the show, as so many weird fossils, such as duckbilled hadrosaurs, horned ceratopsians, pachycephalosaurs and other wonders, date from this time.

Early bloomers

Researchers led by Graeme Lloyd of the University of Bristol, devised a 'supertree' of dinosaur evolution, patiently analysing how more than 450 species, about 70% of the known finds, developed.

They conclude that the big evolutionary splurge for dinosaurs occurred in the late-Triassic, some 225 million to 200 million years ago. This was about 15-40 million years after dinosaurs first emerged.

A second, but smaller, diversification occurred in the mid-Jurassic, some 170 to 160 million years ago.

By that time, all the main dinosaur lineages that existed in the Cretaceous Terrestrial Revolution had been established.

"Our new evidence confirms that the [Cretaceous Terrestrial Revolution] was a key in the origination of modern continental ecosystems, but that the dinosaurs were not a part of it," their paper says.

'Sample bias', the availability of many fossils from this period, could be to blame for the distorted picture, it suggests.

A leading theory for the end of the dinosaurs is that a large asteroid or comet whacked into the modern-day Yucatan peninsula in Mexico, unleashing firestorms and dust clouds that obscured the sun, inflicting climate change that ravaged vegetation.

Smaller creatures, led by mammals, which were able to adapt to the new climate and available food, inherited the planet.

Tags: dinosaurs, fossils, earth-sciences, evolution, palaeontology