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Paleozoic Tetrapod Origins/Radiation: Introduction/Overview.

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Presentation on theme: "Paleozoic Tetrapod Origins/Radiation: Introduction/Overview."— Presentation transcript:

1 Paleozoic Tetrapod Origins/Radiation: Introduction/Overview

2 The Movement to Land origins (mid-late Devonian) sarcopterygian ancestry land invasion of plants & invertebrates

3 Rhipidistian Crossopterygian Ancestry radiations: late Paleozoic/early Mesozoic ancestors to modern amphibians (Temnospondyls) data: skulls, labyrinthodont teeth, limbs/girdles

4 advantages/selective forces influencing the move to land 1.increasingly xeric environment 2.predation pressure 3.absence of competition on land 4.untapped food resource on land (insects) 5.low O 2 levels in warm stagnant pools; lungs preadaptive 6.dispersal opportunities

5 physical properties of air & water 1.density & viscosity 2.gravity 3.temperature extremes 4.oxygen & dissolved gases

6 key problems associated with terrestrial existence 1.Respiration 2.Desiccation 3.structural support & locomotion 4. sensation 5. feeding

7 gravity & support/locomotion; solutions modifications of vertebral column 1.zygapophyses- interlock/link adjacent vertebrae to prevent sagging/twisting 2.notochord replaced by centrum 3.pectoral & pelvic girdles strengthened

8 major structural changes 1. limbs/girdles- better support & muscle attachments 2. skull/jaws- new feeding modes 3. vertebrae- better support 4. lungs

9 Labrynthodont Tooth

10 modifications to the pelvic girdle 1.pectoral girdles free from head; allowing head movement 2.pelvic girdle fused to vertebrae allowing thrust 3.enlarged muscle attachment

11 Pelvic Girdles

12 zygapophyses


14 respiration gills do not function efficiently in air; gill filaments adhere reducing surface area & evaporation lungs are internal respiratory structures that protect from desiccation cutaneous respiration

15 sensory lateral line system relies on density of water changes required for sound detection; sound transfer from air--->fluid

16 reproduction fishes generally have external fertilization & development external fertilization & development is rare among terrestrial organisms; gametes can't withstand desiccation solutions: amniotic/cleidoic egg; air/water barrier



19 Ichthyostega

20 Acanthostega

21 Skull Anatomy

22 Amniotic Egg

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