Axial Skeleton - Ribs Function – Protection – Respiration Phylogeny - new Endochondral

Ribs Dorsal ribs separate dorsal and ventral muscle mass Ventral ribs are in the body wall

Ribs Monocipital (snakes & monotremes) Bicipital – Dorsal head = tuberculum – Ventral head = capitulum

Ribs Costal = vertebral ribs Sternal = costal cartilage

Ribs - Fish Some have no ribs Some have dorsal ribs only (sharks) Some have ventral ribs Some have dorsal & ventral ribs

Ribs - Amphibians Short in anurans and urodeles Long in apodans

Ribs - Reptiles Typically short in neck and long in trunk Turtles – fused to carapace Snakes – long and curved Crocodiles – Gastralia are NOT ribs

Turtle skeleton CarapaceCarapace PlastronPlastron Fused vertebrae RibsRibs

Ribs - Birds Costal & Sternal Ribs Uncinate Processes for muscle attachment

Ribs - Mammals Thoracic (12 in human, 13 in cat) True rib False rib Floating rib

Sternum Needed for stronger & more mobile forelimbs Tetrapod feature only Function – protection, strengthens body wall, attaches muscles, rib attachment Endochondral bone

Sternum - amphibians Frogs & toads – ossified, but poor Urodeles – flimsy if present Caecilians - none

Sternum - reptiles Lizards – large Crocodiles – large cartilaginous plate Snakes – none Turtles – none needed

Sternum - birds Keel Carina For muscle attachment

Sternum - Mammal Segments Xiphoid process is caudal-most segment