(Image source: ScienceNOW)

BY STEVEN SPARKMAN

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What killed the dinosaurs? For 30 years, the idea that an asteroid was the killer has been gaining ground with scientists. But others think the dinosaurs were already gone by the time the meteor struck. Now, a Yale research team claims to have cinched up the “death-from-the-skies” case.

The Yale University press release explains.

“A team of scientists has discovered the youngest dinosaur preserved in the fossil record 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.”

Scientists are pretty much agreed that an asteroid hit Mexico 65 million years ago. They’ve found a layer of dust in the fossil record made of iridium, a substance common in asteroids but rare on Earth. They call that layer the K-T boundary. But the boundary causes a problem.

A writer for io9 explains.

“Until now, paleontologists were unable to find any dinosaur fossils in the three meters below the KT boundary, which is the point where the meteor hit Earth. This strange gap has been interpreted as evidence that dinosaurs were already on the way out long before the meteor hit...”

That three-meter gap meant there were about 100,000 years with no dinosaur fossils leading up to the impact. Proponents of the gradual extinction idea point to the gap as evidence the dinosaurs were already gone. But one of the researchers tells the BBC -- this new fossil closes that gap.

“We found a dinosaur brow horn -- most likely from a triceratops -- and this horn was found just 13 centimeters below the K-T boundary. This indicates that dinosaurs -- at least some dinosaurs -- were doing quite well right up to the meteorite impact that hit 65.5 million years ago.”

Of course, not everyone is convinced. A researcher uninvolved with the study tells ScienceNOW -- a single horn doesn’t make a strong case.

“‘Sadly, it is only one bone’ … the find of a rare fossil 13 centimeters below the K-T boundary could be used in support of both the asteroid impact hypothesis and more gradual extinction scenarios. ... if gradual extinction had occurred, researchers would expect to find fewer fossils as they got closer to the boundary.”

The Yale team says -- with a little extra searching, they’ll eventually be able to close the gap even tighter. But for now the Triceratops is the last dinosaur standing.
 

Transcript by Newsy.