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Giant killer crocs ruled the seas 150m yrs ago

Last Updated: Saturday, September 29, 2012 - 19:14

Washington: A more than 22-foot-long crocodile that ripped prey to death and a huge croc that sucked prey to its doom were at the top of the European marine food chain 150 million years ago, a new study has found.

The enormous prehistoric crocodiles, Plesiosuchus and Dakosaurus, were such voracious carnivores that their methods have been compared to today’s killer whales and a famous, iconic, meat-loving dinosaur.

“The skulls of these two sea croc species have some similarities to T. rex,” Discovery News quoted lead author Mark Young, from the University of Edinburgh, as saying.

“The largest known skull of Plesiosuchus manselii was approximately four feet, three inches long, putting it in the size range of adult T. rex skulls,” he said.

For the study, Young and his colleagues analyzed fossils for the two crocodiles, which were unearthed in sites from England to Germany.

In their U.K. home, the crocs once dwelled in the shallow seas that covered England. At the same time, Archaeopteryx was flying over Europe and giant dinosaurs, such as Diplodocus and Allosaurus, were stomping around North America.

The researchers determined that Plesiosuchus was the largest known species of metriorhynchid, meaning sea crocodile.

“It was bigger than living salt water crocodiles and great white sharks,” Young said.

Its teeth functioned like those of today’s killer whales, based on shape and wear. This ripper crocodile probably bit into both large and small prey, which it would grab, kill and gulp.

Perhaps even more unusual was the sucker croc, Dakosaurus. The skull and jaw characteristics of this nearly 15-foot-long ancient crocodile suggest that it was a suction feeder, making it the first known suction-feeding crocodilian.

This way of eating “involves being able to rapidly open the mouth wide, and generating negative pressure,” Young said.

“This sucks a prey item into the mouth,” he said.

Therefore, both the prehistoric crocodiles fed very similar to modern killer whales. These animals are not related, since killer whales are mammals. The researchers instead believe that the similarities exemplify what’s known as convergent evolution.

“Convergence is the evolution of a similar body plan, feeding mechanism (or other characteristic or behaviour) in two different and not closely related groups, in this case crocodiles and mammals,” Young said.

“The continual evolution of these morphologies in distantly related groups could be telling us something about the limits and optimal method of underwater feeding in vertebrates.

“For example, the shearing, tooth-to-tooth occlusion of Dakosaurus is today found in false killer whales. But over the past 10 million years, numerous species of fossil sperm whales also evolved this feeding mechanism,” he added.

The study has been published in PLoS ONE.


First Published: Saturday, September 29, 2012 - 19:00
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