Nature:

The big difference is the bone structure in its fins. There is an almost complete wrist and finger structure there, not found in any other fish during that era.

They arent saying it walked on land, but that it was the father of land walking creatures.

And even if they found tommorow that the back half of it was fish like, the front half is still enough to show the difference.

And no fish during that time could even slide around on land. So this one was a first.

Ill post more in a bit, I am on my way out the door from work, and then off to a GH2 competition. Wish me luck. =P