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Mammalian Origins and Phylogeny 12 January 2004

Mammalian Origins and Phylogeny 12 January 2004. Announcements for Lecture and Lab The amniote phylogeny Therapsida and the synapsid skull Cynodontia & mammalian grade characteristics Archaic Mammals of the Jurassic Period: Triconodonts, Multituberculates, & Therians

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Mammalian Origins and Phylogeny 12 January 2004

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  1. Mammalian Origins and Phylogeny12 January 2004 • Announcements for Lecture and Lab • The amniote phylogeny • Therapsida and the synapsid skull • Cynodontia & mammalian grade characteristics • Archaic Mammals of the Jurassic Period: Triconodonts, Multituberculates, & Therians • The rise of endothermy & high reproductive rates

  2. Announcements:12-15 January ‘04 • 12-13 Jan. If we have field trips (most likely, & to be confirmed in lecture) then lab sections meet in Rm 234 Jennings for: 1. Review of Mabry et al. 2003 J. Mammalogy 84:20-25 available on line. See E-Journals on Library home page 2. Prepare for squirrel studies: Concepts and procedures • 14-15 Jan. If field trips on 12-13 Jan. , then we meet in Rm 145 Brown Hall (computer lab) 1.Analysis of data collected in Museum with Excel 2. Review & discussion of journal papers within project groups • Taxonomy Take-home due at Examination I

  3. Vertebrate Phylogeny • Fishes (Crossopterygians), Amphibians and Amniotes (reptiles, birds, & mammals) • So what are amniotes? _________________ • First reptiles in the Paleozoic (30 mill. ybp) and the reptilian radiation of the Mesozoic • Primitive reptilian skull types (Fig 3-2 & more)   Synapsid skull ‑ temporal opening bounded above by postorbital & squamosal (below by the jugal & squamosal) • Subclass Synapsida: Orders Pelycosauria and Therapsida • Zygomatic arch: a synapomorphy uniting mammals and their ancestors for over 250 million years.

  4. Origin of mammal-like reptiles Fig 221, Young 1960, Life of Vertebrates

  5. Primitive Reptilian Skull Types Anapsida Synapsida Diapsida Parapsida Feldhamer et al ’99, Fig. 4.1

  6. Synapsid skull Post orbital squamosal Jugal

  7. Mammalian- reptilian line

  8. Cynodontia: A transitional Suborder of the Triassic & Jurassic Periods Vertebrate Phylogeny: Traditional & Cladistic Criteria for identifying archaic mammalian fossils • Secondary Palate & two occipital condyles • Heterodonty (I,C,P,M) from homodont ancestors • Increase in dentary over other bones in the mandible • Stapes, incus (quadrate) and malleus (articular)-Fig 3-8 • Masseter muscle & the zygomatic arch • Jaw articulation to squamosal‑dentaryfrom? ________ • What about physiological changes?

  9. Outline: IA First Reptiles

  10. Fig 3-1 Vaughan

  11. Primitive Therapsid Repile Cynodont Mammal Fig. 3-4

  12. Fig 4.5 Feldhamer

  13. Archaic Mammals of the Jurassic Mammalian radiation of the early Jurassic • Tricondodontia (3 cusps in a row) large (750 g), predaceous mammals of early Triassic • Monotremata: A living example of Mesozoic mammals Fossil record is poor, beginning in early Cretaceous Thought have diverged in Jurassic • Multituberculata: herbivorous, molars w/ multiple cusps Highly successful: from Jurassic to Oligocene (100 m yr) • Zatheria: includes Aegialodon (with tribospenic molar) & ancestor of therian mammals (Eutheria & Metatheria)

  14. Geological Time and the Evolution of Mammals: Pelycosaurs Therapsids Cynodontia: the transitional Infraorder Mammals Fig 4.2, Feldhamer

  15. Triconodontia Multituberculata Fig 4.9 Feldhamer = Fig. 3-15. Vaughan

  16. Archaic Mammals of the Jurassic & Cretaceous * * * Zatheria Tribosphenic molar & “Therian” grade Fig 4.8, Feldhamer

  17. Mammals of the Mesozic: the first two-thirds of mammalian evolution • Rise in early Jurassic and then declined • Early competition with and eventual domination by (dinosaurs) during Jurassic & Cretaceous • Reduction in body size and development of nocturnality • The rise of endothermy in reptiles, birds & mammals Energy requirements of embryos and neonates The avian (& dinosaur?) solution ‑ oviparity & large eggs with parental care after hatching The mammalian solution ‑ viviparity & lactation Evolution of the mammary gland: modified skin glands?

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