New fossil discoveries show predatory marine reptiles from 200 million years ago may have been bigger than today’s blue whales – and that they evolved astonishingly rapidly

By Michael Marshall

PREHISTORIC Earth was a place of monsters. There were 2.5-metre-long millipedes, flying reptiles with 11-metre wingspans and snakes that weighed over a tonne. But if it is the biggest animal of all time you are looking for, conventional wisdom says you don’t need to step back in time. The blue whale is known to reach 30 metres in length and to weigh 199 tonnes. Nothing else in more than half a billion years of animal evolution comes close, not even the largest dinosaur.

Conventional wisdom might be wrong. The fossil record may be concealing an animal that was even bigger than a blue whale. For decades there has been a slow trickle of evidence that a truly enormous super-predator swam the seas between 200 and 250 million years ago. Now, a string of discoveries and reanalysis of previous findings has dramatically bolstered the case.

The implications are far-reaching. We don’t know exactly what this huge animal looked like and it doesn’t even have a name. We have, however, begun to work out how such a gigantic creature could feed itself in the prehistoric seas. Confirmation that it outgrew the blue whale would tell us that we may have drastically underestimated how large toothed carnivores can grow. More than that, the discovery that such leviathans appeared shortly after the most devastating mass extinction in Earth’s history suggests we may need to rethink the factors that drive evolution on such an epic scale.

When dinosaurs ruled the land, several groups of marine reptiles dominated …