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Meteor Wiped Out Dinosaurs, New Fossil Finding Suggests

Meteor Wiped Out Dinosaurs, New Fossil Finding Suggests

 

Fourth grade in Mrs. Allio’s class was when I first learned about dinosaurs. We learned the different types (for some reason, I favored the Brontosaurus) and what they ate, struggled to understand words like “Mesozoic” and “paleontology” and memorized the various theories for why the dinosaurs became extinct (had this happened gradually as temperatures grew warmer? as mammals developed and ate their eggs? Or had a massive meteor hit the earth and wiped the dinosaurs out?).

A new finding in the fossil record provides physical evidence for the latter theory. Scientists have found the the fossilized horn of a ceratopsian — most likely of a Triceratops — that must have lived before the catastrophic meteor impact 65 million years ago. The finding lends weight to the asteroid impact theory, as it suggests that dinosaurs did not slowly die out, but became extinct just prior to the impact.

The fossil was found in the Hell Creek formation in Montana, where other Triceratops fossils have been found. It was found just five inches below the Cretaceous-Tertiary (KT) layer, which is the geological layer that marks the boundary from the Cretaceous period to the Tertiary period 65 million years ago, which is the time the mass extinction of dinosaurs is dated. The discovery suggests that something called the “three-meter gap” — which has been used to support the theory that dinosaurs died out slowly before the meteor impact — does not exist, as noted in Science Daily:

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 10 feet of rock below the K-T boundary. The seeming anomaly has come to be known as the “three-meter gap.” Until now, this gap has caused some paleontologists to question whether the non-avian dinosaurs of the era — which included Tyrannosaurus rex, Triceratops, Torosaurus and the duckbilled dinosaurs — gradually went extinct sometime before the meteor struck. (Avian dinosaurs survived the impact, and eventually gave rise to modern-day birds.)

As Yale graduate student Tyler Lyson, director of the Marmarth Research Foundation and lead author of the study, says,

“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.”

Lyson and his team at first thought the specimen was buried within the K-T boundary by about three feet. Analysis of soil samples helped them to identify the exact location of the boundary, based on a “relative abundance of certain types of fossilized pollen and other geological indicators but is difficult to determine visually while in the field.” Previously, scientists had relied on a visual examination of the actual rock formations in the field to determine the boundary’s location; the soil analysis provides for a more precise sense of where the boundary is. Lyson and his team are now using similar soil analysis to examine other specimens found close to the K-T boundary. He now “suspects that other fossils discovered in the past may have been closer to the boundary than originally thought and that the so-called three-meter gap never existed.”

Which would mean the non-avian dinosaurs did not go extinct prior to a meteor hitting the earth — or whatever happened 65 million years ago.

The study was published in the July 12 issue of Biology Letters.

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107 comments

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1:15AM PDT on Jul 26, 2011

I'm sure either it will be proven again, or maybe they'll come up with other theories just to come back to this one... I don't know.

3:52PM PDT on Jul 21, 2011

I thought everyone had known this for years O__O this is NEWS to you? maybe its just britain but we've had plenty of documentaries explaining exactly what we are almost fully certain happened when they became extinct. there is SO much evidence for the metorite "theory", even from other species.... the metor created a huge crater (in mexico i believe) this obviously caused mass amounts of dust to be thrown up into the atmosphere, which blocked sunlight and MANY species died out, this gave other species a chance to thrive, we suppose humans probably wouldnt exist in the way they do if a metor hadnt wiped out the dinosaur species.
do americans not get taught this?!?!!

9:41AM PDT on Jul 21, 2011

Richard S may be right, but jumps to an unlikely conclusion:
...such fossils are comparitively so rare=> most dinosaurs were not doing fine in the time leading up to the impact.

The available evidence indicates environmental stress was already causing severe survival pressures, when the Chixulub impactor provided the "coup de grace".

ie. everybody is right because multiple factors contributed to the extinction...

There is scientific argument and quantitative data on "so rare" and "severe" pressures. Small and numerous animals, esp. foraminifera are a better index for gauging ecological pressures. And we need to identify some mechanism for pre-impact stresses. Cardiff astrobiologists considered a giant comet fragmenting in Jupiter's neighbourhood - known to happen - that input dust with novel fungi (or novel genes some other way) - to which dinosaurs (and many other species) were vulnerable. The evidence on 'cosmic genes' is in the K/T boundary clays before and after impact.

4:21PM PDT on Jul 20, 2011

"That's odd: if the asteroid caused the extinction why would they become extinct "just prior to the impact"? "Just after" would be more likely."

Yeah, I'm hoping that's just bad editing on their part.

But just for fun...

Imagine a Tyrannosauruses Rex the size of a building, weighing in at several tons looking up into the sky, seeing an asteroid, emitting a high pitched squeal, and then falling over dead from fright. Seconds later the "asteroid" impacts earth, and it's only the size of an acorn.

I think I just created the opening sequence to a new Pixar Movie = Extinction Now! =D

2:11PM PDT on Jul 20, 2011

It's an interesting and thought provoking idea.....theory.........

1:53PM PDT on Jul 20, 2011

"The finding lends weight to the asteroid impact theory, as it suggests that dinosaurs did not slowly die out, but became extinct just prior to the impact."

That's odd: if the asteroid caused the extinction why would they become extinct "just prior to the impact"? "Just after" would be more likely.

12:58PM PDT on Jul 20, 2011

thanks for the great article

12:50PM PDT on Jul 20, 2011

very enlightening and something to think on

4:50AM PDT on Jul 20, 2011

Thanks for the article.

6:34PM PDT on Jul 19, 2011

Well as long as scientists don't decide to bring dinosaurs back,then I will be quite happy.

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