Fingers and toes were long thought to be novelties associated with the invasion of land by tetrapods. The recent identification of a variety of aquatic specializations in some early tetrapods has provoked a debate on whether digits arose in primarily terrestrial or aquatic animals¹,². We recently discovered a pectoral fin of a lobe-finned fish (Fig. 1a, b) that is remarkably similar to tetrapod limbs. This discovery reveals that major tetrapod novelties are also seen in the paddles of some closely related fish and therefore need not have arisen to meet the demands of a terrestrial existence.

1. Vertebrate Biology, Academy of Natural Sciences of Philadelphia, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania 19103, USA and Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA