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"Godzilla" Fossils Reveal Real-Life Sea Monster

Stefan Lovgren
for National Geographic News
November 10, 2005
 
See images of the ancient sea monster >>

Researchers have unearthed fossil evidence of a 135-million-year-old "sea monster" they're calling Godzilla.

A large skull of the animal was found in southern Argentina in an area that was once part of the Pacific Ocean.

Named Dakosaurus andiniensis, the creature is an entirely new species of ancient crocodile. It had a head like a carnivorous dinosaur and a tail like a fish. With its massive jaws and serrated teeth, it preyed on other marine reptiles.

Totally unique among marine crocodiles, "it is one of the most evolved members of the crocodilian family and also one of the most bizarre," said Diego Pol, a paleontologist at Ohio State University in Columbus, who served on the research team.

The research, led by Zulma Gasparini, a paleontologist at Argentina's Universidad Nacional de La Plata, was funded by the National Geographic Society. The discovery is described tomorrow in the journal Science and will appear on the cover of the December 2005 issue of National Geographic magazine.

Carnivorous Dinosaur

The creature's almost intact, 135-million-year-old skull was found in 1996 in Argentina's Neuquén Basin, a region that was once a deep tropical bay of the Pacific Ocean. Prior to the find, researchers had only sketchy fossil evidence of the fearsome sea monster.

They have now established that the giant animal belongs to the crocodyliforms, which include today's crocodiles and their extinct relatives. Marine crocs were abundant during the Jurassic period some 200 million to 145 million years ago. At that time they were found worldwide.

"This [animal] forms a very distinct lineage that appears early on in the evolutionary history of crocodiles—invading the sea and showing outstanding adaptation to the marine environment," Pol said.

Unlike today's crocodiles, Dakosaurus andiensis lived entirely in the water. It measured 13 feet (4 meters) from nose to tail. Instead of legs, Dakosaurus had four paddle-like limbs, used mostly for stability. A fish-like tail propelled the beast through the water.

What made it especially unusual was its snout and teeth.

Until now, every known marine crocodilian had a head of one basic type, with a long snout and many sharp, identical teeth. But "Godzilla" had a short, high snout and teeth that were large and serrated, like a terrestrial reptile's.

"It is more like a carnivorous dinosaur than like a marine crocodilian," said James Clark, a dinosaur expert at George Washington University in Washington, D.C.

Jagged Teeth

Pol says Dakosaurus's anatomical changes over the generations represent "the most drastic evolutionary change in the history of marine crocodiles."

The animal's unusual features suggest that it had completely different feeding habits from its relatives. While other marine crocs fed on small fish, Dakosaurus hunted for marine reptiles and other large sea creatures, using its jagged teeth to bite and cut its prey.

"The most perplexing thing about the animal is that its head shape does not appear to be well suited to a fast swimming crocodilian, because rather than being streamlined, it is somewhat high and flattened from side to side," said Clark, who was not involved with the research.

"Presumably it moved its head mainly up and down rather than sweeping it from side to side, like fish-eating crocodilians."

Other paleontologists expressed admiration over the find.

"This new species is another expression of the incredible diversity of crocodile life during the dinosaur era," said Paul Sereno, a University of Chicago paleontologist and National Geographic Society Explorer-in-Residence.

"If you went to a crocodile worker and said, Let's say you had a chance to evolve something new out of this group, what would you do? And you gave them a pad and a pencil, the last thing they would draw would be a skull that looks like Dakosaurus.

"It's a beautiful example of the unpredictable nature of evolution, and the variety of things that dinosaur-age crocodiles did."

"The cranial anatomy of this species expands the known range of anatomical diversity to a realm no one thought could exist," said Hans Larsson, a paleontologist at McGill University in Montreal, Canada. "It's hard to imagine now a skull shape and ecological role that crocodyliforms did not achieve."

Sereno and Larsson were among a group of paleontologists working in Niger from 1997 to 2000 that found remnants of a 40-foot-long (12-meter-long) crocodilian they dubbed Supercroc.

Sea Monsters

Surprisingly, the nostrils, eye sockets, and other areas of Dakosaurus's skull suggest the animal was more closely related to the smallest of its crocodile relatives than to any of the larger species.

The researchers don't yet know what events triggered the relatively sudden emergence of Dakosaurus, nor do they know what caused it to go extinct.

But scientists do know that it was just one of the "sea monsters" that inhabited the world's oceans 250 million to 65 million years ago.

Others included a Loch Ness monster-like plesiosaur, with a 20-foot-long (6-meter-long) neck, and ichthyosaurs that may have grown to be 75 feet (23 meters) long.

"These groups all went extinct about the same time as the dinosaurs … and the whales appeared shortly afterward and seemed to have replaced them ecologically," Clark said.

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