Not a single transitional form has ever been found showing an intermediate stage between the fin of the crossopterygian and the foot of the ichthyostegid. The limb and the limb girdle of Ichthyostega were already of the basic amphibian type, showing no vestige of a fin ancestry. There is a basic difference in anatomy between all fishes and all amphibians not bridged by transitional forms. In all fishes, living or fossil, the pelvic bones are small and loosely embedded in muscle. There is no connection between the pelvic bones and the vertebral column.
None is needed.
The pelvic bones do not and could not support the weight of the body. These latter fish do not walk, but slither along on their belly, using the same type of motion they use in the water. In tetrapod amphibians, living or fossil, on the other hand, the pelvic bones are very large and firmly attached to the vertebral column. This is the type of anatomy an animal must have to walk. It is the type of anatomy found in all living or fossil tetrapod amphibians but which is absent in all living or fossil fishes.