Permian Most notable event of the Permian is the mass extinction event at the end of the Permian This event was the largest mass extinction in earth’s history 90% of marine species and 70% of terrestrial vertebrates went extinct in just 1- 8 million years

Permian mass extinction Trilobites Rugosan corals

Causes of the Permian mass extinction No one is sure. Three hypotheses have been proposed: Asteroid impact Terrestrial volcanism Stagnant seas degassing carbon dioxide

Cotylosaur Stem Reptiles

Therapsida Mammal-like Reptiles

Thecodontia

Pterosauria

Hadrosaurs (ornithiscians)

Fig

Theropod dinosaur

Deinonychus (theropod)

Plesiosaurs

Ichthyosaurs

Icthyosaurs

Fig b

Cretaceous plants Arrival of the angiosperms changed earth fundamentally During the early Cretaceous, gymnosperms were dominant The angiosperms appeared in the late Cretacous mybp

Angiosperm radiation By the end of the Cretaceous, 50 of the 500 modern families had arisen

Cretaceous insect radiation New groups evolved including the moths, butterflies, ants and bees Are these evolutionary arrivals unrelated to the radiation of angiosperms? I think not! These insects fed on nectar from the flowers Coevolved system - the insects relied on the plants for nectar and the plants relied on the insects for pollination

Fig

Chicxulub crater Chicxulub crater on Mexico's Yucatan Peninsula 125 miles across Many paleontologists believe this crater is the site of the bolide impact that caused the K/T mass extinction Iridium signature around world

Mammals - victors by default Mesozoic were midnight ramblers Mesozoic mammals were poor competitors with dinosaurs Radiation of mammals occurred only after the demise of the dinosaurs

Tertiary mammals All mammals that passed through the K/T boundary were small and insectivorous Required several million years before even moderately sized mammals appeared About 10 my after the K/T boundary, some specialized mammals appeared Bats Whales Manatees

Mesonychid

Andrewsarchus

Ambulocetus

Whale evolution

Hominid evolution At least nine species of hominids existed within the past 4 my Species have overlapped in space and in time Ancestor-descendant relationships are not clear

Australopithecus

Homo habilis

“Out of Africa” model Homo erectus spread into several populations across Eurasia from Africa Only one continent where Homo sapiens evolved, and that was Africa Modern characteristics developed first and were then carried out of Africa

Fig

Support for Out of Africa model Oldest known fossil from Ethiopia - 130,000 years old Oldest fossil known outside of Africa and the Middle East is 40,000 years old Implication that H. sapiens evolved in Africa and migrated to Europe and Asia