Comparative Anatomy. Evolution of the Skeletal System: Post-cranial Skeleton. Functional units of the post-cranial skeleton. Visceal skeleton Vertebral column Ribs Sternum. Girdles Paired appendages Unpaired appendages. Evolution of the Postcranial Skeleton. Postcranial Skeleton.
Evolution of the Skeletal System:
In an aquatic environment, the water acts as a skeleton. Terrestrial organism often have their mass arranged over only a few points of support.Compare and contrast the articulations of the 2 joints shown here.
Note: among aquatic forms there is prob-ably a lot of convergence. Note also that the function of the trunk musculature changes from aquatic forms to terrestrial forms: from locomotion to support.