Fossils show dinosaurs thrived till 350,000 years pre-extinction; asteroid impact caused their sudden end
New Mexico fossils show dinosaurs stayed diverse until asteroid impact, disproving gradual decline theory
Photo Credit: Wikimedia Commons
Recent discoveries indicate that dinosaurs were going very strong till the impact of a massive asteroid on Earth 66 million years ago. A dinosaur community is rich and diverse. Fossils of a site in New Mexico have been dated to a few hundred thousand years after the impact. The findings negate the initial assumption that dinosaurs were already in decline at the time when the asteroid hit.
According to As per the new research, scientists re-examined rock layers in New Mexico's San Juan Basin (the Naashoibito Member) using radiometric and magnetic methods. They found the youngest dinosaur-bearing layers date to about 66.38 million years ago, just about 350,000 years before the extinction event.
This revision (from previous estimates of ~70 million years) means New Mexico's dinosaurs lived nearly up to the end of the Cretaceous – roughly the same time, for example, as Triceratops in Montana. The team identified hadrosaurs (duck-billed dinosaurs) and the giant sauropod Alamosaurus, evidence of a flourishing ecosystem right before the impact.
The newer dates emphasize separate dinosaur communities that lived in different areas. Thus, the southern (New Mexico) fossils comprise crested duckbills and colossal sauropods, whereas the northern sites (Montana/Dakotas) have Triceratops and flat-headed hadrosaurs. This geographic "provinciality" most likely indicates that the differences in climate were the cause rather than a collapse of the same fauna throughout the whole area.
Paleontologist Steve Brusatte comments, "There is no sign that these dinosaurs were in any trouble, or that anything unusual was happening to them, or that they were in any type of long-term decline". Coauthor Andrew Flynn agrees that with these dates, dinosaurs "were not on their way out" before the asteroid impact.
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