The tetrapodomorphs (part of the sarcopterigians (Sarcopterygii) or lobe finned fish) played an important role in the Orcadian Basin and eventually the evolution of man.
In the lake, these fast swimming fishes with their strong teeth were the top predators. They are evolutionary closely related to the first vertebrate land animals during the Upper Devonian.
The similarity of the skull, dermal skull bones and the bony structure supporting the paired fins are striking when compared with the first vertebrate land animals.
The sarcopterygians (except the dipnoans) were thought to be extinct, but in 1938 a strange fish was caught at sea in South Africa by a local fisherman. This specimen was presented to Marjorie Courtenay-Latimer who worked at the local natural history museum in East London, South Africa. Later this fish was identified by the fish expert Dr James Smith as a coelacanth. Fossil coelacanths are known from many localities and ages. The first well preserved specimens came from Germany, found in the same Jurassic limestones that are so famous for the bird-like dinosaur Archaeopteryx. This discovery had an impact on the scientific community comparable with the finding of the tomb of Tutankhamun.
The coelacanths are a member of the Actinistia which is another group of sarcopterygians. Whilst coelacanths are not found in Orkney other sarcopterygians are, like the tetrapodamorphs mentioned above. The sarcopterygians found in Orkney are grouped as: