BEST OF 2009: Bizarre band of paleo-crocs

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Paleontologists Paul Sereno and Hans Larsson excavate the fossil skull of a 100-million-year-old croc in Niger. The animal, which they nicknamed BoarCroc, was one of several crocs that inhabited a lost world now buried in the sands of the Sahara. (Credit: Mike Hettwer/National Geographic)

U. CHICAGO (US)/MCGILL (CANADA)—A suite of five ancient crocs, including one with teeth-like boar tusks and another with a snout like a duck’s bill, have been discovered in the Sahara.

The five fossil crocs, three of them newly named species, are remains of a bizarre world of crocs that inhabited the southern land mass known as Gondwana some 100 million years ago.

Paul Sereno, a University of Chicago paleontologist and National Geographic Explorer-in-Residence, and his team unearthed the strange crocs in a series of expeditions beginning in 2000 in the Sahara. Many of the fossils were found lying on the surface of a remote, windswept stretch of rock and dunes.

The crocs galloped and swam across present-day Niger and Morocco, when broad rivers coursed over lush plains and dinosaurs ruled.

“These species open a window on a croc world completely foreign to what was living on northern continents,” Sereno says.

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BoarCroc, a 20-foot-long, upright meat eater. (Illustrations: Todd Marshall)

The five crocs, along with a closely related sixth species, will be detailed in a paper published in the journal ZooKeys and appear in the November 2009 issue of National Geographic magazine. The crocs also will star in a documentary, “When Crocs Ate Dinosaurs,” to premiere at 9 p.m. ET/PT Saturday, Nov. 21, on the National Geographic Channel.

At 40 feet in length and weighing 8 tons, Sarcosuchus imperator, popularly known as SuperCroc, was the first and largest of the crocs Sereno found in the Sahara, but it was not the strangest, Sereno says. He and his teams soon discovered key fossils of five previously unknown or poorly understood species; most of them walked “upright,” with their arms and legs under the body like a land mammal instead of sprawled out to the sides, bellies touching the ground.

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DogCroc, an agile galloper and capable swimmer

The crocs and their nicknames:

  • BoarCroc: New species, Kaprosuchus saharicus; fossils found in Niger. Twenty-foot-long upright meat-eater with an armored snout for ramming and three sets of dagger-shaped fangs for slicing. Closest relative found in Madagascar.
  • DogCroc: New fossils of named species, Araripesuchus wegeneri. Fossils found in Niger include five skeletons, all next to each other on a single block of rock. Three-foot-long, upright plant- and grub-eater with a soft, doglike nose pointing forward. Likely an agile galloper, but also a capable swimmer. Closest relative in Argentina.
  • DuckCroc: New fossils of previously named species, Anatosuchus minor. Fossils found in Niger. Three-foot-long, upright fish-, frog- and grub-eater. Broad, overhanging snout and Pinocchio-like nose. Special sensory areas on the snout end allowed it to root around on the shore and in shallow water for prey. Closest relative in Madagascar.
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DuckCroc, a 3-foot-long, upright animal with a long nose

  • PancakeCroc: New species, Laganosuchus thaumastos; fossils found in Niger and Morocco. Twenty-foot-long, squat fish-eater with a three-foot, pancake-flat head. Spike-shaped teeth on slender jaws. Likely rested motionless for hours, its jaws open and waiting for prey. Closest relative from Egypt. The scientific paper also names a close relative discovered by the team in Morocco, Laganosuchus maghrebensis.
  • RatCroc: New species, Araripesuchus rattoides; fossils found in Morocco. Three-foot-long, upright plant and grub-eater. Pair of buckteeth in lower jaw used to dig for food. Closest relative in South America.

“We were surprised to find so many species from the same time in the same place,” says paleontologist Hans Larsson, associate professor at McGill University in Montreal and a team member who discovered the bones of BoarCroc and PancakeCroc. “Each of the crocs apparently had different diets, different behaviors. It appears they had divided up the ecosystem, each species taking advantage of it in its own way.”

To better understand how these ancient crocs—mostly upright and agile—might have moved and lived, Sereno traveled to northern Australia, where he observed and captured freshwater crocs. Realizing while

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PancakeCroc, a 20-foot-long fish eater with a 3-foot, pancake-flat head

there that he may have stumbled onto one of the keys to crocodilian success, Sereno saw freshwater crocs galloping at full speed on land and then, at water’s edge, diving in and swimming away like fish. On land they moved much like running mammals, yet in a flash turned fishlike, their bodies and tails moving side to side, propelling them in water.

Based on interpretation of the fossils, Sereno and Larsson hypothesize that these early crocs were small, upright gallopers. In the scientific paper, they suggest that the more agile of their new croc menagerie could not only gallop on land but also evolved a swimming tail for agility and speed in water, two modes of locomotion suggested to be evolutionary hallmarks for the past 200 million years.

“My African crocs appeared to have had both upright, agile legs for bounding over land and a versatile tail for paddling in water,” Sereno writes in the National Geographic magazine article. “Their amphibious talents in the past may be the key to understanding how they flourished in, and ultimately survived, the dinosaur era.”

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RatCroc, a 3-foot-long, upright plant- and grub-eater

To study the crocs’ brains, Sereno CT-scanned the skulls of DuckCroc and DogCroc and then created digital and physical casts of the brains. The result: Both DogCroc and DuckCroc had broad, spade-shaped forebrains that look different from those of living crocs. “They may have had slightly more sophisticated brain function than living crocs,” Larsson says, “because active hunting on land usually requires more brain power than merely waiting for prey to show up.”

To collect the croc fossils, Sereno and his teams endured temperatures topping 125 degrees Fahrenheit, living for months on dehydrated food. Logistics were challenging: For the 2000 expedition, they transported trucks, tools, tents, five tons of plaster, 600 pounds of water and four months’ worth of other supplies.

Sereno’s research and field expeditions were funded by the National Geographic Society and the Whitten-Newman Foundation.

University of Chicago news: http://news.uchicago.edu/

chat9 Comments

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9 Comments

  1. dnarom

    The National Geographic article came out ages ago…

  2. Viraldi

    Crocoduck Found!

  3. Stephen W. O'Driscoll

    Evolution is known for throwing curve balls, but five of them at once? Who says God doesn’t have a sense of humor?

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  6. BebeKashmir

    I’m so glad this happened while Kirk Cameron and Ray Comfort are alive. I can’t wait to see them squirm when somebody forces them to deal with this

  7. GREG

    WHOSE RESPONSIBLE THIS??

  8. NobodysSon

    I have a pet duck that often stalks around hissing when she is in a bad mood that causes us to refer to her as our little dinosaur. Now I know her true ancestor: duckcroc!

  9. the anonymous

    why did the artist depict every one of these proto-crocs with the mouths wide open? crocs keep their mouths closed most of the time and so do even large carnivores. the images make them seem like ferocious killers (or monsters) and could be mistaken for concept artwork for something like a star wars film. how about showing them doing something other than their best t-rex impersonation? these animals are thought to have lived in a land of “lush plains” and “broad rivers”, not the planet Dagobah.

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