The lungfish from the Devonian Orcadian Basin are well known and described in great detail in many publications. A new species of dipnoan, Pinalongus saxoni was identified recently and will be named after the famous local fossil expert Jack Saxon who died in 2005.
Lungfish are fishes which have the ability to breathe air utilising lungs. Lungfish are still found today and some of them look very much the same as their Devonian ancestors.
Dipterus valenciennesi is the the most common lungfish found in the Devonian rocks of Orkney. In the sediments indicating deep to shallow water conditions, Dipterus is almost always there although you often find only the scales. Dipterus probably could handle some of the very hostile conditions in the drying-out lakes more than the other fishes.
Higher up in the sequence in the Eday Flags, Pentandia macroptera, a new species of lungfish appeared together with other new fish species.
Lungfish have a very specialized way of feeding which can be found from the Devonian up to the recent lungfish. They posses large tooth plates which can be found on the palate and the lower jaw. The tooth plates have in most species tubercles in ridges on the surface, the teeth. Probably these structures in the Devonian lungfish were used to crush tiny invertebrates like arthropods or small fish. Maybe they were partly scavengers.
Formerly scientists thought that lungfish were the fishes giving rise to the first amphibians and land animals. When the first crossopterygians, the lobed-finned fishes, were described in more detail (Gregory 1911, Jarvik and others) they became recognised as the true ancestors of the first land animals. See also on this website the Crossopterygians.