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Amphibians

Amphibians. No scales in skin; mucous glands abundant; cutaneous _______________ Moveable eyelids; ________ glands Ear sensitive to airborne or ground-borne vibrations. Muscular, protrusible __________ _____________ divided into small and large regions

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Amphibians

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  1. Amphibians • No scales in skin; mucous glands abundant; cutaneous _______________ • Moveable eyelids; ________ glands • Ear sensitive to airborne or ground-borne vibrations. • Muscular, protrusible __________ • _____________ divided into small and large regions • Larval gills lost at metamorphosis (except for paedomorphic forms) • Heart has single ventricle, subdivided atrium • Nitrogen eliminated primarily as _________ • External fertilization; adults return to water to reproduce

  2. Labyrinthodonts Lissamphibians

  3. Early Tetrapods Labyrinthodonta Tiktaalik (“fishapod”) • Late Devonian (360 MYA), found in Ellesmere Island, Canada • Fish or tetrapod? the most primitive “tetrapod” known to date • Most likely completely aquatic Plesiomorphies: Apomorphies:

  4. Tiktaalik rhipidistian fish

  5. Acanthostega • Late Devonian (360 MYA), found in Greenland • Also very similar to rhipidistian fishes • predominantly _____________ Plesiomorphies: • well-developed ________________ • intracranial _________ • well-ossified gill arches suggest functional internal gills • deep tail supported by finrays • lateral line system • labyrinthodont __________ Apomorphies: • paddle-like limbs with eight digits • weight-bearing girdles • tetrapod pattern of skull bones

  6. Ichthyostega Acanthostega

  7. Labyrinthodonta Ichthyostega • very similar to Acanthostega • no _______________ • skull more ____________ than Acanthostega • postcranial skeleton more ________________ • large overlapping ribs • frontlimbs much larger than hindlimbs Lepospondyli • solid ______________ • small size • some entirely aquatic with small limbs and “horned” hydrofoil skulls

  8. Expansion onto land

  9. Lissamphibia • labyrinthodont ancestors • origin in the ________________ • reduced bones in ________________________ • scales lost except in Apoda • skin respiration • pedicellate teeth Urodela (Caudata; salamanders) • No ____________ and no temporal notch • External and internal fertilization

  10. Lissamphibia

  11. Anura (frogs) • Numerous skeletal modifications for _________________ • External fertilization • Tadpole larval stage and metamorphosis • Have tympanum Apoda • __________________ • Burrowing lifestyle • ____________ skull • Internal fertilization • Some lay eggs, other viviparous

  12. Anurans (Salientia) Apoda Urodela (Caudata)

  13. Neotenic salamanders retain gills as adults (paedomorphosis)

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