This fish is from the youngest fish-bearing Subgroup on Orkney, the Eday flags. There is a great deal of resemblance with the well know species Eusthenoptheron foordi from the Upper Devonian of Miguasha, Canada. The species Eustenopteron foordi has been described by Jarvik in great detail in several publications.
This medium to large sized osteolepid is found at the base and higher up in the Rousay Subgroup. In the fish beds it is common, often together with the tiny arthrodira Millerosteus minor. In the sediments, indicating a shallow water condition only scales and plates of the head can be found. The scales look very much like those of Gyroptychius milleri.
This osteolepid is found in Caithness below the Achanarras horizon and should be present in Orkney below the Sandwick Fish Bed, however, the species has never been positively identified in sediments from Orkney. John Flett Brown has found osteolepid scales in sediments of the Lower Stromness beds near Stromness and we presume that they belong to Thursius macrolepidotus but the head is needed for identification.
This small to medium sized osteolepid is well known from Caithness but articulated specimens from Orkney are rare. It is often found as disarticulated remains, heaps of scales or loose plates from the head. Probably this fish had a very short stratigraphical range.
A very common fish in the Sandwick Fish Bed and well known from the excellent descriptions and reconstructions by Jarvik (1948). This middle-sized osteolepid probably preyed on the smaller acanthodians and juvenile fish it could handle.
This osteolepid is similar to Gyroptychius agassizi but there are some slight differences in the dermal plates covering of the skull roof. In the field the most notable feature is the deep notches for the eyes. The species can be found as loose scales and plates in sediments above the Sandwick Fish Bed.