Bridging the gap

After my morning swim, I hauled myself out of the water by my fore limbs on to the pool-side, the land if you like to call it that....just like my tetrapod ancestors did 350 million years ago...and not too far from where I did the same thing this morning.

A few miles from the swimming pool, palaeontologist Stan Wood discovered fossils that revealed the process when vertebrate life forms moved from the seas to the land. True, Scotland then wasn't quite where Scotland is now. It was a good bit south of the equator and part of a land of shallow seas, lagoons, coastal flood plains and tidal mudflats. 

These have given us sandstone, mud-stone and cement-stone deposits along the Whiteadder river at a spot eponymously named Willie's Hole, a deep pool below a natural weir.

The river bed and the local sea cliffs have both yielded specimens of great importance so I just had to go and take a look.

Layers of sedimentary rocks along the river bank

 

 

It made for a pleasant stroll along the river bank with alder carrs and mallards for company and a walk back over 350 million years

Willie's Hole

It was here that the fossils were found that bridged the so-called Romer's gap, the "gap" in the fossil record from water dwelling tetrapods to land dwelling forms. The gap is named after the man who first noted the problem.

A small but fully explanatory exhibition of the fossils at The National Museum of Scotland outlines the finds and their significance.

http://www.nms.ac.uk/fossilhunters 

Why the four limbed terapods hauled themselves on to the land isn't yet clear but they did and they breathed air and that is why I was breathing air and hauling myself out of the water millions and millions of years later.

What our tetrapod ancestor may have looked like

The tetrapod fossils from before 345-360 million years ago showed creatures with four limbs that were not strong enough to support them on land and those after Romer's gap were well adapted to life on land, the ones from Willies Hole show the development of a ribcage and limbs strong enough to make the transition. I really appreciate the effort they made!