Mass Extinctions
1) end of the Guadalupian 70% of marine species died out, including most reef fauna and large fusilinids, onset of deep sea anoxia
2) terminal Permian extinction 80% of all species went extinct (C isotope curve), associated also with onset of global water column anoxia
proposed to be a meteor impact (Becker 2001)
Evidence: crater not yet found, buckeyballs filled with helium (no Ir), sand dikes
Early Mesozoic Terrestrial Animals: The Age of Dinosaurs Begins
Only two places have a sedimentary fossil record that spans
the PT boundary:
Karoo basin of South Africa
Ural Mountains of Russia
Just before the PT, the Late Permian mammal-like reptiles disappear suddenly
At the start of the Triassic, therapsids re-diversified but barely survived into the Jurassic
True mammals evolved from therapsids in the Late Triassic, but dinosaurs evolved slightly earlier in the Late Triassic and rose to dominance
Dinosaur Origins
Inherited locomotion from the thecodonts, which evolved in
the Early Triassic
Resembled bipedal thecodonts, with different skulls and teeth
Dinosaurs and crocodiles evolved from thecodonts
Dinosaurs did not become gigantic before the Late Triassic, but did reach 6 meters
Late Triassic
therapsids lived alongside dinosaurs, amphibians, and reptiles
extinction event of most therapsids and marine life
set the stage for the dominance of dinosaurs
Early Jurassic
Rapid evolution of giant dinosaurs
Dinosaur Phylogenetic Relationships
Characterized by different pelvic structures:
Ornithischians (bird-hipped) herbivores
Sauraschia (lizard-hipped) herbivores and carnivores
Largest of all dinosaurs were the sauropods (saurachia)
Late Jurassic Morrison Formation of western US contains the most diverse assemblages of both ornithischains and suarishians
Frogs and Turtles small reptiles that originated in the Triassic
Late Triassic pterosaurs evolved and took to the air
Late Jurassic first birds, Archaeopteryx, Solenhofen
Limestone, dinosaurs with feathers, lacked a breast bone so a
weak flyer