360-345 million years ago, Scotland was a very different place. Lying close to the Equator, the vegetated land was hot, humid and subject to droughts and flooding. It was in this setting that a major evolutionary event occurred: tetrapods (backboned animals with four limbs) invaded land.

But, for many years, scientists had no idea how this had happened. There was a 15 million year ‘gap’ in the fossil record – no tetrapod fossils had been found dating from this missing time period, so there was no evidence to show how this giant step had taken place.

It was a Harvard professor, Alfred Sherwood Romer, who identified this hole in the fossil timeline, and so it became known by scientists as ‘Romer’s Gap.’