At the start of the 19th century the lungfish Dipterus was one of the first fish described in many papers. It has peculiar tooth plates and a strange lower jaw. Together with this, and the fact that there are still lungfish living today, it makes this a very interesting fish. On Orkney articulated specimens can be found in the Sandwick Fish Bed and disarticulated specimens almost everywhere. In the Eday Subgroup Dipterus is “replaced” by Pentlandia macroptera.
Most likely for protection against predators, and the harsh environment the fish has cosmine on the scales and headplates. Juvenile fish however had no cosmine and the scales and headplates are not shiny. The plates on top of the head, the cranial shield, are very simple in juvenile fish but become more complex in bigger specimen. In adult specimens the cranial shield as well as the other plates and scales are cosmine covered.