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Dinosaur decline started long before asteroid impact
Time:06-04-2017  Hits:11

The dinosaurs — the so-called tyrants of the Mesozoic era — weren't exactly thriving during their last few million years on Earth, a new study finds.


The new analysis of the dinosaur family tree reveals that dinosaurs were disappearing even before the asteroid hit about 65.5 million years ago. Roughly 24 million years before that impact, dinosaur extinction rates passed speciation rates, meaning that the animals were losing the ability to replace extinct species with new ones, the researchers said.


The study isn't the first to suggest that dinosaurs were in a major decline before the asteroid event. In previous studies, scientists have recorded the number of species in each geological age and compared those levels to the subsequent ages (each age lasts for millions of years) to get a sense of how diverse the dinosaurs were, Sakamoto said.



But that method focuses on snapshots in time and doesn't take into account the extinction and speciation rate within each branch of the dinosaur family tree. So the researchers of the new study looked at the dinosaur fossil record and the family tree to get a robust picture of when new dinosaur species came onto the scene, Sakamoto said.


"Our study is the first to incorporate such phylogenetic [family tree] information when studying speciation and extinction in dinosaurs," Sakamoto told Live Science. "This is what has allowed us to build a more nuanced and certain picture of dinosaur speciation than has ever before been possible."

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