Aves: birds • Most scientists refer to this group as Sauropsida • Birds are a part of the Dinosauria clade. Why? • This means dinosaurs are still around! • All non-avian dinosaur clades died off in the Cretaceous extinction
Tetrapods: Reptiles Emerald tree boa Vestigial hind limb bones Broad-tailed hummingbird
Xiatingia zenghi • Birds are thought to have evolved from theropod dinosaurs during the Jurassic period • Archaeopteryx and Xiaotingia are pre-birds which were close relatives (but not the ancestors) of modern birds Archaeopteryx lithographica Reptiles: Birds
• Synapomorphies which contribute to flight: • Feathers – modified scales • Air sacs – pump air through lungs and bones • Reduction of organs • Lightweight bones Reptiles: Birds
Reptiles: Birds • Tons of diversity – over 10k species!
National Geographic, 2013 • Tons of diversity – over 10k species! Reptiles: Birds
Mammal Phylogeny • Over hundreds of millions or years, synapsids eventually give rise to mammals
Mammals § Synapomorphies that arose in the mammal MRCA: • Mammary glands – secrete milk (fats + sugars + proteins + vitamins + antibodies!) • Hair – made of keratin (also makes up reptile scales and feathers!) •
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- Spring '14
- Evolution, placental mammals, tetrapods