Dinosaur discovery boosts meteor theory

Illustration of a large meteor impact with Earth

Evidence is strong that a huge meteor impact 65 million years ago led to the demise of the dinosaurs.

SCIENTISTS HAVE DISCOVERED the fossilised remains of a dinosaur that was alive not long before the catastrophic meteor impact 65 million years ago. The finding indicates that dinosaurs did not go extinct prior to the impact and provides further evidence as to whether the impact was in fact the cause of their extinction.

Researchers from Yale University discovered the fossilised horn of a ceratopsian—likely a Triceratops, which are common to the area—in the Hell Creek formation in Montana last year.

Yale graduate student Stephen Chester

Yale graduate student Stephen Chester discovered the last known dinosaur before the catastrophic meteor impact 65 million years ago.

They found the fossil buried just five inches below the K-T boundary, the geological layer that marks the transition from the Cretaceous period to the Tertiary period at the time of the mass extinction that took place 65 million years ago.

Since the impact hypothesis for the demise of the dinosaurs was first proposed more than 30 years ago, many scientists have come to believe the meteor caused the mass extinction and wiped out the dinosaurs.

But a sticking point has been an apparent lack of fossils buried within the three metres of rock below the K-T boundary. The seeming anomaly has come to be known as the “three-metre gap.”

Dinosaurs were doing fine

Until now, this gap has caused some palaeontologists to question whether the non-flying dinosaurs of the era—which included Tyrannosaurus rex, Triceratops, Torosaurus and the duckbilled dinosaurs—gradually went extinct sometime before the meteor struck. (Flying, or avian, dinosaurs survived the impact, and eventually gave rise to modern-day birds.)

“This discovery suggests the three-metre gap doesn’t exist,” said Yale graduate student Tyler Lyson, director of the Marmarth Research Foundation and lead author of the study, published online July 12 in the journal Biology Letters.

Illustration of primitive mammals and a Triceratops skeleton

Three small primitive mammals walk over a Triceratops skeleton, one of the last dinosaurs to exist before the mass extinction that gave way to the age of mammals.

“The fact that this specimen was so close to the boundary indicates that at least some dinosaurs were doing fine right up until the impact.”

While the team can’t determine the exact age of the dinosaur, Lyson said it likely lived tens of thousands to just a few thousand years before the impact.

“This discovery provides some evidence that dinosaurs didn’t slowly die out before the meteor struck,” he said.

The team is now examining other fossil specimens that appear to be buried close to the K-T boundary and expect to find more, Lyson said. He suspects that other fossils discovered in the past may have been closer to the boundary than originally thought and that the so-called three-metre gap never existed.

Adapted from information issued by Yale University. Images courtesy NASA / Mark Hallett / Tim Webster.

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