Complex sentence: The arms had deep pits and stout proesses for attachment of muscles and ligaments, the humerus was large, with stout epipodials, and the ulna had a stout olecranon, indicating powerful arms.
Split into simpler sentences: The arms had deep pits and stout proesses forattachment of muscles and ligaments, which indicates they were powerful. The humerus was large, with stout epipodials, indicating powerful arms.