In with the NEW and out with the OLD, or a mix of BOTH discovered in early land vertebrates.

Catherine Boisvert in this week's issue of Nature discribes the pelvic fin endoskeleton and associated partial pelvis of Panderichthys, a close tetrapod relative. The unusal anatomy of the pelvic fin is much more primitive then expected given the advance anatomy of the pectoral fin endoskeleton, which was previously described by Vorobyeva in 1995. The fin is characterized by massive bones; including large femur, fibula, fibulare, and intermedium bones all suggestive that Panderichthys used its pelvic fins as anchors during body undulation to move on land. It was not until the leg-powered Acanthostega appeared that tetrapods really started to walk, rather than wiggle on land.

Boisvert, Catherine A.(2005) The pelvic fin and girdle of Panderichthys and the origin of tetrapod locomotion. Nature 10.1038/04119