Paleogene Period Phanerozoic

the paleogene spans extinction of dinosaurs, 66 million years ago, dawn of neogene 23 million years ago. features 3 epochs: paleocene, eocene , oligocene.

basilosaurus (a whale, despite name)

the paleocene epoch began k-t extinction event caused impact of metorite in area of present-day yucatan peninsula , caused destruction of 75% of species on earth. paleocene saw recovery of earth event. continents began take modern shape, continents (and india) separated each other. afro-eurasia separated tethys sea, , americas separated strait of panama, isthmus of panama had not yet formed. epoch featured general warming trend, , jungles reached poles. oceans dominated sharks large reptiles had once ruled became extinct. archaic mammals, such creodonts , primates evolved during mesozoic filled world. during time there no land creatures on 10 kilograms. mammals still quite small.

the eocene epoch ranged 56 million years 34 million years. in eocene, land animals small , living in cramped jungles, paleocene. none had mass on 10 kilograms. among them primates, whales , horses along many other forms of mammals. @ top of food chains huge birds, such gastornis. time in recorded history birds ruled world (excluding ancestors, dinosaurs). temperature 30 degrees celsius little temperature gradient pole pole. in middle eocene epoch, circum-antarctic current between australia , antarctica formed disrupted ocean currents worldwide, resulting in global cooling, , caused jungles shrink. allowed mammals grow; such whales mammoth proportions, were, now, aquatic. mammals andrewsarchus @ top of food-chain , sharks replaced basilosaurus, whales, rulers of seas. late eocene epoch saw rebirth of seasons, caused expansion of savanna-like areas, along evolution of grass.

the oligocene epoch spans 33 million 23 million years. oligocene featured expansion of grass had led many new species take advantage, including first elephants, cats, dogs, marsupials , many other species still prevalent today. many other species of plants evolved during epoch also, such evergreen trees. long term cooling continued , seasonal rains patterns established. mammals continued grow larger. paraceratherium, largest land mammal ever live evolved during epoch, along many other perissodactyls in event known eocene–oligocene extinction event (grand coupure).