We were always looking over our shoulders; we saw lots of tracks.

When we look inside the fin, we see a shoulder, we see an elbow, and we see an early version of a wrist, which is very similar to that of all animals that also walk on land.

The world is filled with puzzles, all kinds of interesting questions and it's our challenge to figure them out. It's not just like this static file cabinet of things that human beings know. It's ever expanding.

What we saw was a real mosaic between characteristics of fish and those previously thought to be only in land animals. The fossil was showing us how creatures were assembled over time to live on land.

It represents the transition from water to land - the part of history that includes ourselves. When we talk about the fish's wrist, we're talking about the origin of parts of our own wrist.

Most of the major joints of the fin are functional in this fish.