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Ancient Sea Monster Remains Found in Argentina

Argentine scientists have discovered the remains of a fierce sea monster that terrorized Pacific waters in the age of the dinosaurs. The researchers are calling it Godzilla after the legendary movie monster, but it really was an ancestor of modern crocodiles.

What has a head like a meat eating dinosaur and a tail like a fish? An ancient sea reptile called a dakosaur.

Millions of years ago when dinosaurs ruled the land, these early crocodiles dominated the oceans, but they never seem to have caught the public's imagination as dinosaurs have.

Perhaps this will change with the discovery of a 135- million-year-old dakosaur skull and two lower jaws in the Patagonia desert of southern Argentina. The researchers who describe it in the journal Science call it Dakosaurus andiniensis, the Andean Dakosaur, to contrast it to those that swam in other parts of the world at the time. What a contrast it is.

"At first glance, it was evident that Dakosaurus andiniensis was truly unique among marine crocodiles," said Diego Pol, an expert on ancient animals at the Ohio State University.

He took part in the research and says the creature was distinct from its crocodile cousins of the Jurassic era because it had a tall, short head shaped like a bullet and large, powerful, serrated teeth that seem to belong in a dinosaur's mouth.

These features indicate that it was a predator capable of gobbling reptiles and other large sea life, filling a niche eventually taken over by large sharks. In contrast, other dakosaurs and their modern crocodile descendants have long, thin snouts and many thin teeth suitable for feeding on smaller, more agile prey such as fish.

"We find these results extremely interesting because they indicate that the diversity of crocodiles back in the Jurassic was much greater than expected," he added.

Based on the size of the skull, Mr. Pol and his colleagues from the National University of La Plata, Argentina estimate that the creature was four meters long. They infer its body shape based on a computer program that analyzed the fossils and found that they most resemble the early crocodile branch that had flippers and a fish-like tail instead of four feet and a tail like modern crocodiles.

"This analysis revealed that the anatomical changes along the evolution of the Dakosaurus lineage were clearly the most drastic evolutionary change in the history of marine crocodiles. This places the 135-million-year-old Dakosaurus andiniensis not only as one of the most recent members of this family, but also as the most bizarre marine crocodile known today," he explained.

The National Geographic Society in Washington, which sponsored the research, says dakosaurs were only one of the monsters that cavorted in the world's oceans between 250 million and 65 million years ago. Back then shallow seas and a lack of significant marine predators created new opportunities for many reptiles that had first developed on land. They included such beasts as giant ichthyosaurs that might have reached 25 meters in length and plesiosaurs with seven-meter-long necks reminiscent of the fabled Loch Ness monster in Scotland.

Diego Pol says that all dakosaurs became extinct by the end of the Cretaceous era 65 million years ago, leaving us with only a fraction of the crocodile diversity of that long ago time.

"This pattern of extinctions is what we see in the fossil record of all species. It is fairly common to see that a species or family has its own moment where it diversifies and later goes extinct. The most famous case of this is the large dinosaurs that disappeared by the end of the Cretaceous," he said.

You might call these ferocious meat-eating dakosaurs, the dinosaurs of the sea, animals that shared the world at the same time.

Although they are no longer around, their smaller crocodile descendants, who split their time between land and water, are no friendlier and might just as well be avoided.