This is footprint of early tetrapods. We have here, for example, digits, impressions, and something like their pads. This is important.

 

I've been working personally in this field since the mid 1990s. I've had over 20 publications in 'Nature', and this is the most important paper that I have ever worked on.

 

Footprints in a Polish quarry tell the tetrapods which walked the earth 20 million years before we thought any animal had left the sea.

 

This is your little friend, isn't it? Oh my word. Oh, wonderful. Look at that!

 

Until only a few months ago, this was an accurate model of a kind of animal paleontologists believed existed in the Middle Devonian Period, with fins but no proper feet. The new model is quite different. 

 

Legs stick out and thighs can flex forwards. Then, it had to be an animal like this, a primitive land vertebrate, not a fish.

 

And if you are not sure you believe it, the Nature paper and the full film offer the proof.