There are many changes that allowed the pelvic girdle of "Acanthostega" to become a weight-bearing structure. In ancestral states the two sides of the girdle were not attached. In "Acanthostega" there in contact between the two sides and fusion of the girdle with the sacral rib of the vertebral column. These fusions would have made the pelvic region more powerful and equipped to counter the force of gravity when not supported by the buoyancy of water. 