Originally, the extinction of the dinosaur that occurred sixty-six million years ago was thought to have paved the way for mammals to dominate, but a new study shows that mammals died off alongside the dinosaurs. Metatherian mammals thrived while living next to the dinosaurs during the Cretaceous period. A study conducted by an international team of experts on mammal evolution and mass extinctions, shows that these over abundant mammals nearly disappeared with the dinosaurs.
A ten kilometer wide astroid struck near what is now Mexico at the end of the Cretaceous and unleashed a global cataclysm of environmental destruction, some two third of all metatherian living in North America died. After this massive extinticion, the metatherians would never regain their numbers which is why they are so rare today and largely restricted to unusual environments in Australian and South American. Animals that give birth to well-developed young took advantage of this demise and now thrive. They are found all across the globe range from mice and men.
A ten kilometer wide astroid struck near what is now Mexico at the end of the Cretaceous and unleashed a global cataclysm of environmental destruction, some two third of all metatherian living in North America died. After this massive extinticion, the metatherians would never regain their numbers which is why they are so rare today and largely restricted to unusual environments in Australian and South American. Animals that give birth to well-developed young took advantage of this demise and now thrive. They are found all across the globe range from mice and men.
http://www.sciencedaily.com/releases/2014/12/141217101314.htm