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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 - PowerPoint PPT Presentation
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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
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
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.
Fig 221, Young 1960, Life of Vertebrates
Origin of mammal-like reptiles
Primitive Reptilian Skull TypesAnapsida
Feldhamer et al ’99, Fig. 4.1
Synapsida
Parapsida Diapsida
squamosalPost orbital
Jugal
Synapsid skull
Mammalian-
reptilian line
Cynodontia: A transitional Suborder of the Triassic & Jurassic Periods
Vertebrate Phylogeny: Traditional & CladisticCriteria for identifying archaic mammalian fossils 1. Secondary Palate & two occipital condyles 2. Heterodonty (I,C,P,M) from homodont ancestors3. Increase in dentary over other bones in the mandible4. Stapes, incus (quadrate) and malleus (articular)-Fig 3-8
5. Masseter muscle & the zygomatic arch 6. Jaw articulation to squamosal‑dentary from? ________7. What about physiological changes?
Outline: IA
First Reptiles
Fig 3-1 Vaughan
Primitive Therapsid Repile
Cynodont Mammal
Fig. 3-4
Fig 4.5 Feldhamer
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)
Geological Time and the Evolution of Mammals: Pelycosaurs TherapsidsCynodontia: the transitional Infraorder
MammalsFig 4.2, Feldhamer
Triconodontia
Fig 4.9 Feldhamer = Fig. 3-15. Vaughan
Multituberculata
Zatheria Tribosphenic molar & “Therian” grade
Archaic Mammals of the Jurassic & Cretaceous
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*
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Fig 4.8, Feldhamer
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?