LECTURE 8: Cenozoic Era 65 mya - Present

What were the Significant Events of the Cenozoic Era? Age of Mammals (Adaptive Radiation) Rodents, Hooved mammals, carnivores First Primates HUMANS!!! Adaptive Radiation of Birds and Angiosperms Continents move to Present Locations Warm, Tropical Climates then cooler, drier grasslands

What are the Mammal Groups? Differ in Reproduction Monotremes Hatch from eggs- platypus Marsupials Born before they are fully developed and continue development outside the womb, often in a pouch -kangaroo and opossum Placentals Develop completely in their mother’s wombs before they are born- such as humans, horses, dogs, etc

What is Fossil Lake? Wyoming was once a warm, tropical lake Waters were rich in calcium carbonate, due to runoff from surrounding limestone and dolomite mountains Quick burial prevented the organisms’ bones, teeth, and sometimes even soft tissues such as scales and feathers from decaying Fossils are Holotypes Used to classify fish fossils

Diplomystus dentatus Leidyosuchus wilsoni

Masillosteus janei Amphliplaga brachiptera

Dragonfly Jumping Spider

What caused the Climate Change? Moving continents caused the Earth’s climate to begin shifting from warm and wet to cooler and drier- 45 mya New waterways created cold currents As continents moved, new seaways opened at the poles. Cold polar water flowed where it hadn’t before, cooling global temperatures New mountains interrupted rain patterns Colliding continental plates buckled Earth’s crust, forming massive mountain ranges. Mountains blocked moist air currents blowing in from the ocean, creating dry environments further inland This cooler, drier climate was just right for hardy grasses, which spread across—and transformed—the continents

What did Climate Change due to Mammal Evolution? Until now, mammals had been small With large, open, grasslands: mammals were able to roam large distances Hooved Animals diversified and got larger and started grazing Taller teeth with more enamel can withstand constant chewing of gritty grass without being worn away Longer limbs with fewer toes are better for outrunning predators and traveling long distances. (Fewer toes make for lighter feet.)

Leptomeryx evansi Menodus

What is the Affect of Grazers? Coevolution: Carnivores! Cats/Dogs- 35 mya Efficient Hunting Techniques Hunted in Packs Surprise ambush Early Hyena

South America and Convergent Evolution Nimravid carnivoran skull Hoplophoneus primaevus South Dakota Saber-toothed marsupial skull Thyllacosmilus atrox Argentina- South America Different Species, Same Tools On separate continents, two predators from different sides of the mammal family tree faced the same challenge. They had to hunt large prey to survive. Though the two species were only distantly related, natural selection favored the same trait in both—saber-teeth—for meeting this challenge. While the predator on the left is a North American carnivoran, the predator on the right is a South American marsupial—a completely different mammal group. Yet both of these predators have saber teeth, terrific for piercing thick hides of large prey

Terror bird (theropod dinosaur) Andalgalornis ferox South America In most of the world, carnivoran mammals were the top predators. But in South America, lack of competition from mammals may have allowed terror birds like this one to play that role With their long legs, terror birds may have been able to sprint at speeds close to 40 miles per hour, catching and stunning prey with their sharp beaks

How did Whales Evolve? Fossils tell us these ancient whale ancestors were four-footed mammals with hooves From land-dwelling ancestors, the first whales evolved for life spent partly on land, partly in the sea With webbed feet, they could swim; with long limbs, they could move about on shore Within ten million years, whales were fully aquatic Webbed front feet evolved into paddle-like flippers. Hind limbs all but disappeared, as a broad tail fluke evolved for more powerful swimming

What were the First Primates? Altiatlasius – 60 mya Somewhat squirrel-like in size and appearance Grasping hands and feet that were increasingly more efficient in manipulating objects and climbing trees Developing effective stereoscopic vision