Jurassic crocodiles and modern killer whales

Fossil skulls of crocodylians Dakosaurus maximus (A) and Plesiosuchus manselii (B). © Young et al. (2012)/Phil Hurst NHM

From The Scotsman in Scotland:

Snap! Ancient crocodiles just like killer whales, Scottish scientists discover


Published on Wednesday 19 September 2012 00:00

SCOTTISH experts have found a link between killer whales and ancient crocodiles which suggests that today’s reptiles don’t deserve their “living fossil” ­reputation.

Researchers at the University of Edinburgh used fossilised ­remains from the Natural History Museum in London of two giant crocodylians, Dakosaurus maximus and Plesiosuchus manselii, to reconstruct their huge heads.

To their surprise, they found that the shape and size of the creatures’ teeth and skulls matched those of modern killer whales which now swim in the same British seas inhabited by the reptiles 150 million years ago.

The findings suggest that both species evolved the same hunting and feeding techniques, which challenges the widespread view that crocodiles have hardly changed since prehistoric times.

Dakosaurus had a bullet-shaped snout for suction-feeding and badly worn teeth, like some killer whales today, leading experts to conclude that it swallowed fish whole and also ate tough-skinned sharks.

Meanwhile, the teeth of the Plesiosuchus showed no wear and tear, suggesting that it had adapted like modern-day “type two” killer whales to be even more brutal, possibly devouring other marine reptiles of the time.

Dr Mark Young, lead researcher at the University of Edinburgh’s School of GeoSciences, said: “A lot of people refer to [modern] crocodiles as living fossils, but we have found that ancient marine crocodiles seem to have fed like killer whales do now, which means they were probably as evolved as mammals are today.”

The ancestors of today’s crocodiles were more than four metres long and both belonged to the Metriorhynchidae family. Their front limbs had modified into flippers to adapt to life in the oceans and they had a shark-like tail fin, giving them a very different appearance to crocodiles today.

At that time while dinosaurs like the diplodocus walked the plains of America, the seas were teeming with giant pliosaurs which dominated the marine food chains.

The findings from the study, published in the scientific journal PLoS ONE, also help to explain how so many ancient reptiles survived for so long – and could help to predict what the impact of global warming might be on killer whales in future.

Dr Young added: “We’ve never really understood how so many different species survived in such close proximity then – we would expect they would out-compete or even eat each other. This seems to show that they were able to survive ­because they evolved to feed in different ways.

“We are now looking at why they became extinct and whether there are links between what happened to the ancient crocodiles at that time and what could happen to killer whales today as a result of climate change.”

While different types of killer whale exist in other parts of the world, until recently only one type was known to live in the waters around the UK.

In 2010, Scottish scientists in Aberdeen reported finding a second type of the marine mammal in the North Atlantic which, unlike the first, suffered virtually no wear to its teeth even in the oldest adults. Dr Andy Foote from the University of Aberdeen, who carried out the study, concluded that while the first type of killer whale sustains massive damage to its teeth because it sucks up herring and mackerel, the new type has evolved to feed differently, in order to find a new ecological niche.

See also here. And here.

9 thoughts on “Jurassic crocodiles and modern killer whales

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