Evolution: early mammals and dinosaur extinction (Introduction)

by David Turell , Saturday, June 11, 2016, 22:53 (3087 days ago) @ David Turell

It appears from new research that mammals were well diversified when dinosaurs went extinct, and had been around 10-20 million years:-https://www.sciencedaily.com/releases/2016/06/160607220628.htm-"New research reports that, contrary to popular belief, mammals began their massive diversification 10 to 20 million years before the extinction of the dinosaurs. -***-"The researchers analysed the molars of hundreds of early mammal specimens in museum fossil collections. They found that the mammals that lived during the years leading up to the dinosaurs' demise had widely varied tooth shapes, meaning that they had widely varied diets. These different diets proved key to an unexpected finding regarding mammal species going extinct along with the dinosaurs.-"Not only did mammals begin diversifying earlier than previously expected, but the mass extinction wasn't the perfect opportunity for mammal evolution that it's traditionally been painted as. Early mammals were hit by a selective extinction at the same time the dinosaurs died out -- generalists that could live off of a wide variety of foods seemed more apt to survive, but many mammals with specialised diets went extinct.-"The scientists involved with the study were surprised to see that mammals were initially negatively impacted by the mass extinction event. "I fully expected to see more diverse mammals immediately after the extinction," said lead author David Grossnickle, a Field Museum Fellow and PhD candidate at the University of Chicago. "I wasn't expecting to see any sort of drop. It didn't match the traditional view that after the extinction, mammals hit the ground running. It's part of the reason why I went back to study it further -- it seemed wrong."-"The reason behind the mammals' pre-extinction diversification remains a mystery. Grossnickle suggests a possible link between the rise of mammals and the rise of flowering plants, which diversified around the same time. "We can't know for sure, but flowering plants might have offered new seeds and fruits for the mammals. And, if the plants co-evolved with new insects to pollinate them, the insects could have also been a food source for early mammals," he said."-Comment: The old theory that mammals had to wait until dinosaurs were gone to do much development is not correct. Advancing from egg-laying reptiles to mammals is as giant step, but the duckbilled platypus is a definite intermediate form. Hard to deny common descent from this evidence.