The most recent dinosaur fossil, discovered in the Hell Creek formation, Connecticut last year, is leading scientists to question how exactly dinosaurs died out around 65 million years ago.
Unearthed by researchers from Yale University, the findings about the fossil are documented in the Royal Society Biology Letters journal, published online July 12.
It is a 45 centimeter ceratopsian horn, most likely from a triceratops, many of which have been found in this region.
The significance of the fossil lies in its underground location—just five inches (13 centimeters) below a layer known as the K-T boundary.
This is the dividing line between the Cretaceous period (K, the “Age of Dinosaurs”) and the Tertiary Period (T, the “Age of Mammals”). It marks the K-T extinction or mass extinction about 65.5 million years ago, when non-avian dinosaurs disappeared along with some other animals and plants.
About 60 percent of all species discovered below the K-T boundary have not been found above it. According to a leading extinction theory, this apparent sudden loss is due to an asteroid that created the Chicxulub crater in Mexico.
But the region spanning 10 feet (3 meters) below the K-T boundary is significantly short of fossils.
This factor led to a gradual extinction theory in the 1980s proposing that dinosaurs could have died out long before the cosmic impact due to climate change and sea level changes caused by increased volcanic activity and continental drift towards the end of the Cretaceous.
However, the arrival of the horn fossil could undermine this gradual extinction theory.
“This discovery suggests the three-meter gap doesn’t exist,” said Yale graduate student Tyler Lyson, lead author of the study and director of the Marmarth Research Foundation, in a press release.
"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," he added.
But just because “we had one dinosaur in the gap doesn’t necessarily falsify the idea that dinosaurs were gradually declining in numbers,” Lyson told LiveScience.
He is hopeful that more fieldwork within the gap will uncover more dinosaur fossils.
While many may not disagree with the cosmic impact theory, we still do not know just how this asteroid could have rendered so many species extinct.
A wide range of hypotheses exist, ranging from a subsequent nuclear winter that killed many plants to a thermal pulse from the collision that microwaved the Earth and cooked up everything on land.
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