Ancestors that dominated the Permian And Early Triassic Triassic Takeover Dominance of dinosaurs may have driven some therapsids to a nocturnal insectivorous lifestyle this may have selected for hair and ID: 1026853
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1. MAMMALS I
2. From Therapsid Ancestors that dominated the Permian And Early Triassic“Triassic Takeover” - Dominance of dinosaurs may have driven some therapsids to a nocturnal, insectivorous lifestyle. - this may have selected for hair and endothermy, leading to the first mammals (Morganucodontids). - lactation may have evolved, initially, to keep eggs moist. Monotremes still do this.
3. Jurassic and Cretaceous radiations of small, nocturnal mammals.But, the largest yet discovered, Repanomamus giganticus, was about the size of an otter (1 meter, 30 lbs.) and ate vertebrates, including young dinosaurs (in gut contents).
4. Extant Mammals:Three major clades:MonotremesMarsupialsPlacentals
5. Extant Mammals:Three major clades:MonotremesMarsupialsPlacentals
6. Pygmy possum – Australia(opossums in Western Hemisphere)Extant Mammals:Three major clades:MonotremesMarsupialsPlacentals
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9. Extant Mammals:Three major clades:MonotremesMarsupialsPlacentals
10. 5. Major PhylaDeuterostomes: l. Chordata Vertebrata Gnathostomes Tetrapods - AmniotesMammals - Monotremes: egg laying, “sweat” milk - Marsupials: live birth to embryo – attaches to nipple to complete development. Mother does not need to abandon the nest/young to feed. - Placentals: Longer internal development allows for precocial behavior (independence on birth); placental allows for direct, energy-efficient transfer of nutrients between blood systems of mother and offspring. FOODDIGESTIONNutrients in bloodstream of motherMilk production in mammary glandsFOOD for OFFSPRINGDIGESTIONNutrients in bloodstream of offspringPlacentaEach energy transformation is less than 100% efficient
11. The extinction of the Dinosaurs at the K-T boundary correlates with the radiation of most major groups of mammals in the Cenozoic.Primates and Xenarthans (orange) are the exceptions, beginning their radiation before K-T boundary.The changing face of the molecular evolutionary clockSimon Y.W. HoPublished:July 30, 2014DOI:https://doi.org/10.1016/j.tree.2014.07.004AfrotheriaXenarthaEuarchontogliresLaurasiatheriaAtlantogenataBoreoeutheriaAlso, correlates with Pangaea breakup in to Gondwana and Laurasia, and then breakup of Gondwana into SA and Africa
12. Marsupials and XenarthansLaurasians and Afrotheres(Notably carnivores, camels, horses, rodents)2.7 myaGreat American Interchange40 mya From Africa: Rodents and Primates
13. 5400 living species50% are rodents20% are batsAfrotheriaXenarthaEuarchontogliresLaurasiatheriaAtlantogenataBoreoeutheria
14. Mammals of South CarolinaMarsupalia: Didelphidae Virginia opossum (Didelphis virginiana)XenarthaNine-banded Armadillo (Dasypus novemcinctus)