Watsonosteus fletti (Watson)

This big placoderm, which could reach a length of about a meter at its maximum, occurs in the Eday Subgroup where it is very rare. Again there are some differences in the morphology of the dermal plates of the head and body, but in overall view it compares well with the other arthrodires found on Orkney. Only Homostius milleri has a different  morphology.

Feeding habits are still vague but there are strong indications that it was living on or near the bottom of the river or lake. The picture shows a complete fish with tail and a partly disarticulated specimen.

From the specimens available, Miles (1963) compares in a drawing (below) reconstructions from the median-dorsal plates of some of the arthrodira.

From the pictures of the  specimens on this web page it is clear that his reconstruction of the medium-dorsal plate of W. fletti is incorrect.

 

Complete fish with tail

Scattered specimen showing most of body plates and head

Head of scattered specimen

Median-dorsal plate, external view

Median-dorsal plate, internal view

Nuchal plate, external view (cast)

Nuchal plate, internal view (cast)

Reconstruction of head in dorsal view (after Miles, 1963 )

Reconstruction of body in lateral view (after Miles, 1963 )

Reconstruction of median dorsal plates of A: Coccosteus, B: Dickosteus, C: Watsonosteus (after Miles, 1963 )