Elements of appendicular skeleton: f li b Elements of appendicular ...

Context of evolution of tetrapod limb
• Late Silurian – Devonian (410-400 mybp):
– Diversification of plants into semi-aquatic and terrestrial
habitats.
– Formation of wetlands and rivers with abundant plant
life.
– Appearance of terrestrial insects.
• Transition from fin to limb preceded that from aquatic
to terrestrial habitats.
– Early limbs sufficient for shallow, muddy waters.
– Multiple, clearly defined digits.
– Weak girdles and limbs, weak wrists.
• Tetrapods: reduction of dermal bone, elaboration of
endochondral elements.