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Dinosaurs evolved from their smaller ancestors in just a few million years and not the 10 million years or more scientists had suspected, according to a new study. The work, based on radioactive dating of rocks sandwiching the earliest fossils of those predecessors, suggests that paleontologists have long misjudged the overall pace of dinosaur evolution.
Dinosauromorphs, are a broad group of creatures that lived in parts of the ancient supercontinent Pangaea that are now South America and southern Africa. That group includes all dinosaurs but also includes their earlier predecessors and their subsequent kin.
But it turns out that those fossils aren't well-dated.
Unearthed from rocks in northwestern Argentina, fossil dinosauromorphs were previously thought to have lived anywhere between 237 million and 247 million years ago, a 10 million year period.
But uranium-lead dating, in which researchers estimate the age of a rock by comparing its concentrations of radioactive uranium and the lead it decays into, tells a different story.
A younger volcanic deposit lying in the rock above these fossils includes zircons, tiny bits of silicate mineral that often contain trace amounts of uranium. Those zircons crystallized about 234 million years ago.
And older sediments below the fossils contain zircons that crystallized about 236 million years ago.
So, not only all dinosaurs, but many of their predecessors, must have evolved between those two dates, a short-ish two million year period.
Story carried by ScienceNews, the original study published by the National Academy of Sciences.
(Score: 2, Interesting) by Anonymous Coward on Wednesday December 09 2015, @09:08PM
I don't think ALL dinosaurs evolved in 2 million years, nor do I think it was ever believed to be 10 million years. I always heard it was more like a period of over 150 million years.
Perhaps they are referring to all the earliest-period proto-dinosaur ancestors, which is a vague and dubious claim to say the least.
(Score: 2) by Joe Desertrat on Thursday December 10 2015, @02:45AM
I would think there will be a lot of revision of fossil ages over time. Dating techniques have greatly improved and expanded in the last thirty or so years, and they are still getting better.