(A) Ventral view of the mandible and associated skull elements. (B) Mandible and skull elements labeled. (C) Left lateral view of the mandible. Abbreviations: an, angular; art, articular ...

Regardless of age or sex, the skeletal system can be broken down into two parts, known as the axial skeleton and the appendicular skeleton. The adult axial skeleton consists of 80 bones.

If we are correct and the axial morphology did not permit lateral trunk flexion in Ichthyostega, two gaits seem theoretically possible: ‘walking’ with diagonally synchronized limb movements ...