References in periodicals archive ?
The mammal community, they report in the July 23 NATURE, changed markedly 33.5 million years ago, just after the end of the Eocene epoch. A world dominated by rhinolike creatures and many medium-size mammals gave way to one ruled by rodents and rabbits.
The nearest major extinction came some 2 million years later, at the end of the Eocene epoch.
Even so, these resilient mammals went extinct about 35 million years ago, at the end of the Eocene epoch.
Previous analyses of cores drilled in this region revealed ice-rafted debris dating back to the middle Eocene epoch, prompting suggestions that ice appeared in the Arctic about 46 million years ago.
He looked through the North American mammal record to see how species responded to three periods of extreme climate change during the last 40 million years: a global cooling during the Eocene epoch, 37 million years ago; a severe cooling in the early Oligocene, at 33 million years ago; and a drying in the Miocene at 7.5 million to 7 million years ago.
Before the cooling occurred at the end of the Eocene epoch, the Earth was warm and wet, and even the north and south poles experienced subtropical climates.
Indeed, the ostrich has its origins in the Eocene epoch, about 55 million years ago.
Paleontologists have discovered fossils of cat-sized horses that scampered across northwestern Wyoming about 50 million years ago, during the Eocene epoch. Called Hyracotherium sandrae, the newly identified species is the oldest known horse in North America, reports Philip D.
"Leaf-eating did not happen overnight," Strahl told SCIENCE NEWS, adding that some fossil evidence indicates the hoatzin may have originated in the Eocene epoch, predating mammal foregut fermenters.