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

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

Anuran Anatomy

“protrusible tongue”

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

Salamander Anatomy

A few Oklahoma Amphibians

Amphibians of SE Oklahoma