"This is also the part of the Eocene when we see the most new appearances of mammals due to evolutionary innovation, rather than immigration," said Stucky, who is curator of paleoecology and evolution at the Denver Museum of Nature & Science. Some 30 new rodents, carnivores, primates and artiodactyls (the group that includes sheep, goats, camels, pigs, cows, deer, giraffes and antelopes, among others) appeared on the scene.
But then, as temperatures declined again, the number of mammal genera dropped to a low of 84, with the complete loss of many mammalian groups that previously were well represented. Lower temperatures and a dryer climate continued to influence mammal and plant evolution as savanna habitats began to emerge.
Until this research, the consensus among paleontologists who study North American vertebrates was that climate played only a background role in supporting the evolution of mammals during the Paleocene and Eocene (65 million to 35 million years ago) and that only at the end of the Eocene, when Antarctic glaciations began, did Earth's climate deteriorate enough to cause observable changes in land mammal diversity.
"Our paper documents the fact that global change affected plants and animals on a wide scale," said Gunnell, an associate research scientist and vertebrate collection coordinator at the U-M Museum of Paleontology. "Some plants and animals flourished while others suffered."
When considering today's global warming, Woodburne said, "The question is, on which side of this picture will mankind be found?"
|Contact: Nancy Ross-Flanigan|
University of Michigan