美国国家公共电台 NPR Scientists Unveil Ancient Sea Monsters Found In Angola

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STEVE INSKEEP, HOST:

The first line of this next story sounds like it ought to be spoken by the narrator of a movie. When the Atlantic Ocean was young, sea monsters ruled. This is a true story. Some of their bones have turned up along the coast of West Africa. They go on exhibits soon at the Smithsonian Institution in Washington, D.C., fossils that tell a sometimes-bloody story of birth and death in the ocean. Here's NPR's Christopher Joyce.

CHRISTOPHER JOYCE, BYLINE¹: I've come to the National Museum of Natural History to look for a big, swimming, carnivorous reptile². A section of the oceans exhibit is walled off from view. A sign says, sea monsters unearthed³ - do not enter. A staff member lets me in. Next to a folding table, geology student Yasmin Jackson (ph) is unwrapping boxes full of fossils.

YASMIN JACKSON: These are mostly real bones that we're dealing⁴ with so I have to be very gentle.

JOYCE: Knowing that it's 80 million years old.

JACKSON: Seventy-two million years old.

JOYCE: Sorry.

JACKSON: (Laughter).

JOYCE: These bones are here at the nation's premier⁵ Natural History Museum because they're unusual. They were found in the rocky cliffs of Angola overlooking the Atlantic Ocean. Angola is not a country known for fossils. Few scientists have looked there. Half a century of civil war made it too dangerous. But geologically, Angola, on the west coast of Africa, is special. Two-hundred-billion years ago, Africa was part of the supercontinent. Then that continent started unzipping down the middle.

Eventually, Africa and South America drifted apart. The South Atlantic Ocean filled in the gap between them. And then sea creatures moved in. Paleontologist Louis Jacobs from the Southern Methodist University has been digging in Angola since 2005. He says fossils from its coastline tell the story of the ocean's earliest days.

LOUIS JACOBS: And you have an ocean where you didn't have one before, and now you have fossils of these marine⁶ monsters that are found there. So why did that happen, and why is it them that are there?

JOYCE: The marine monsters were mosasaurs - giant, swimming reptiles⁷. To acquainted with mosasaurs, I went to SMU in Dallas. At the paleontology department, Jacobs leads me down into the basement then a long and dark hallway to where his colleague, Michael Polcyn, has been reconstructing a mosasaur from the Angolan bones.

Wow.

JACOBS: I told you that he was putting it together in his living room.

MICHAEL POLCYN: This is my dining room.

JOYCE: Bones of all shapes and sizes sit on shelves. But the eye-catcher is a half-built mosasaur hung up on rods and wires, the sinuous⁸ tail and neck, the rib⁹ cage and a feeble-looking arm.

POLCYN: Let me adjust this.

JOYCE: Polcyn adds what look like elongated¹⁰ fingers to one of the arms. And, voila, it's a front limb, a mosasaur paddle. The big tail provided thrust. The animal's four paddles helped it navigate¹². Mosasaurs looked part-lizard and part-orca but grew up to 50 feet long, about the length of school bus. They probably had scales and a powerful tail fin¹¹ similar to a shark's.

JACOBS: The way mosasaurs move is like lizards¹³, where their bodies flex¹⁴ a lot from side to side.

POLCYN: You can see it was a very optimized¹⁵ swimmer. This was a pursuit predator¹⁶.

JOYCE: There are more rooms and lots more bones. Polcyn says Angola was a mosasaur jackpot.

POLCYN: The first time we set foot there, it was incredible. You couldn't walk one pace without coming across another fossil. The ground was just littered with fossils.

JOYCE: One in particular tells a grisly story. It's a mosasaur skeleton, complete, lying flat on the table just as it was found in the Angolan rock - the looping spine¹⁷ and tail, the head twisted back in death, 3-inch-long teeth, 3-foot-long jaws¹⁸. There are two sets of smaller bones coiled halfway¹⁹ down the beast, as well as some random²⁰ shark's teeth. Jacobs explains what happened.

JACOBS: This is three different mosasaurs in the stomach.

JOYCE: The big one, and two small ones it ate.

JACOBS: And then after the big fella died, you see the shark's teeth from where it was scavenged.

JOYCE: The shark's teeth came out as they ripped the flesh off the dead mosasaur. These and other fossils from Angola will be on view at the new exhibit at the Smithsonian in November then the original bones go back to Angola. Jacobs says their story is more than just how big and scary ancient reptiles could be. It's about how a new ocean and the conditions for new life were created, how trade winds stirred up deep water full of nutrients²¹. The nutrients attracted fish and big turtles, and they attracted even bigger sharks and ultimately giant reptiles.

JACOBS: Geology controls destiny in the sense that biology has to adapt to the stage that it's put on.

JOYCE: It was a drama that might have continued if an asteroid²² hadn't hit the Earth and wiped out the giant reptiles and their dinosaur²³ cousins, opening the door to us, the furry²⁴, little mammals. Christopher Joyce, NPR News.