Paleozoic Tetrapod Origins/Radiation. rhipidistian crossopterygian ancestry. mid-late Devonian (360-370 mya) major structural changes: limbs/girdles- better support & muscle attachments skull/jaws- new feeding modes vertebrae- better support lungs.
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rhipidistian crossopterygian ancestry • mid-late Devonian (360-370 mya) • major structural changes: • limbs/girdles- better support & muscle attachments • skull/jaws- new feeding modes • vertebrae- better support • lungs
hierarchical classification of the tetrapod vertebrates • Tetrapoda (vertebrates with four limbs) • Amphibia • Lissamphibia (modern amphibians) • Gymnophiona • Caudata (salamanders)- Jurassic ~ 140 mya • Anura (frogs & toads)- Triassic ~ 200 mya
Modern Amphibians: Lissamphibia • general features: • 'amphibious' life cycle (metamorphosis) • smooth, glandular skin • three chambered heart • carnivorous
Order Anura • distribution cosmopolitan except Antarctica; tropics especially • elongate hind limbs & powerful leg muscles • strong pelvis fused to the vertebral column; posterior vertebrae fused into a urostyle • feeding: sticky, protrusible tongue • reproduction: • species specific vocalizations • external fertilization; amplexus
Order Caudata • distribution: primarily northern hemisphere • paedogenesis- larvae becomes sexually mature • courtship: species specific displays (visual, tactile, & chemical cues) • internal fertilization; spermatophore transfer • eggs laid in water or moist soil; larvae; aquatic & gilled in many