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Lecture 14 - LECTURE OUTLINE 1 What are mammals and how are...

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LECTURE OUTLINE 1) What are mammals and how are they distinguished from reptiles? 2) When did mammals evolve and who were their ancestors? 3) Examine three key innovations in the origin of mammals: the ear, endothermy, and limb posture.
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CLASS MAMMALIA Subclass Prototheria : monotremes (egg-laying) Subclass Theria : marsupials and placentals (live birth) SOFT TISSUE CHARACTERS: Hair Mammary glands / lactation Endothermy What distinguishes mammals from reptiles?
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MAMMALS vs. REPTILES : Osteological Differences Jaw joint between dentary and squamosal 3 middle ear bones Complex bony respiratory turbinates Teeth that are replaced only once Teeth with 2+ roots Jaw joint between quadrate and articular 1 middle ear bone Minimal or no respiratory turbinates Teeth that are continuously replaced Teeth with single roots SPRAWLING SEMI-ERECT ERECT Limb Posture in Mammals vs. Reptiles
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First Amphibians 370 ma First Amniotes 300 ma EARLY AMNIOTE, a.k.a. “STEM REPTILE”, circa 300 Ma MAMMALS Synapsids BIRDS DINOSAURS REPTILES Sauropsids “STEM REPTILES”
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SYNAPSIDS a.k.a. MAMMAL-LIKE REPTILES SAUROPSIDS Dinos , birds, living reptiles STEM REPTILES Mammal-like reptiles • Pelycosaurs • Therapsids • Cynodonts PERMIAN TRIASSIC
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Phase 1 : PELYCOSAURS : Dimetrodon PELYCOSAURS : extinct by mid-late Permian. THERAPSIDS CYNODONTS
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Phase 2 : THERAPSIDS LYSTROSAURUS, a herbivore The late Permian was “The Age of Ugliness” THERAPSID CARNIVORE?
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Therapsid sabertooth carnivore attacking therapsid herbivore R.T. Bakker PELYCOSAURS THERAPSIDS CYNODONTS Therapsids suffer multiple extinctions at PT boundary.
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Phase 3 : Cynodonts PELYCOSAURS THERAPSIDS CYNODONTS
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The Triassic therapsid, Thrinaxodon .
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  • Winter '10
  • MORRIS,M.R./FRISCIA,A.R./MOLDWIN,M.B./VANVALKENBURGH,B
  • jaw joint, Synapsid, cynodonts, Evolution of mammalian auditory ossicles

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