Armoured Fish

Physical Description

Coccosteus cuspidatus is one of the larger fish (20-45cm in lenght) from the Orcadian Basin. Coccosteus is covered in bone plates from the tip of its head until about halve way its body, of which the rest is soft tissued. Its mouth could open really wide so it could take a big chuck out of the thing that it is eating. This is made possible because certain bony plates on the head where not fused together. How to identify a Coccosteus cuspidatus? Well that is quite easy, as Coccosteus as distinct pores on its head armour which is not present in other placodermi which can be found nearby.

Age and Distribution

Coccosteus cuspidatus is from the Middle Devonian of Scotland. This fish lived approximately 385 million years ago. At the time this area of Scotland was part of the Orcadian Basin, which was a huge complex of lakes that stretched for hundreds of miles. During this period plants started to rapidly colonize the land and fishes dominated nearly every niche of seas and lakes, hence why this period is also known as the “Age of Fishes”. Mesacanthus pusillus co-inhabited the lake with other fishes like the acanthodian Mesacanthus, Diplacanthus, the osteolepids Osteolepis, Gyroptychius and Thursius, the lungfish Dipterus, the porolepid Glyptolepis, the enigmatic Paleospondylus gunni, and the placoderms Dickosteus, Pterichthyodes, Millerosteus, Rhamphodopsis and Homostius.

About the Placodermi, 

Evolutionary Significance

The earliest Placodermi are known from the lower Silurian, then in the Devonian (like all other fishes) they diversified and eventually in the late Devonian some becoming the six metre monster Dunkleosteus. Scientists believe that the Placoderms went extinct at the end of the Devonian period, as there is no fossil evidence of them found in the Carboniferous.

Taxonomy

Coccosteus cuspidatus belongs to the Coccosteidae which is a subclass of the Placodermi (which means “plate skinned”) There are no other known Coccosteidae from Middle Devonian of Scotland, but the genus is represented in other locations in the world.