By comparison with modern fishes such as zebrafish, it has long seemed that the limbs of tetrapods are evolutionary innovations unique to tetrapods, but here Marcus Davis and colleagues instead studied Hox-gene expression in the development of the fins of a 'living fossil'. The paddlefish, common in the seas more than 250 million years ago, has Hox-gene patterns long considered to be tetrapod hallmarks, showing that some aspects of limb development are primitive and common to all bony fish, but which have apparently been lost in highly evolved fishes such as the zebrafish.
- Marcus C. Davis
- Randall D. Dahn
- Neil H. Shubin
