Pterichthyodes milleri Armoured Fish Fossil


Name: Pterichthyodes milleri

Location: North of Scotland

Lenght: 9.5 cm / 3.5 inch

Age: Middle Devonian

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About Pterichthyodes milleri placoderm

Physical Description

Pterichthyodes milleri is one of the armoured fish (5-35cm in lenght) from the Orcadian Basin. Pterichthyodes is covered in bone plates from the tip of its head until about halve way its body, of which the rest is soft tissued. P.milleri fins look like arms, when it was first discover it was thought to be a turtle instead of a fish. It is believed that this fish lived at the bottom of the lake where it could use its “arms” to crawl along the lakebed. Its eyes are located right at the front of the head looking forwards and upwards.


Age and Distribution

Pterichthyodes milleri 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”. Pterichtyodes milleri co-inhabited the lake with other fishes like the acanthodians Mesacanthus, Diplacanthus and Cheiracanthus, the osteolepids Gyroptychius, Osteolepis, and Thursius, the lungfish Dipterus, the porolepid Glyptolepis, the enigmatic Paleospondylus gunni, and other placoderms Dickosteus, Coccosteus, Millerosteus, Rhamphodopsis and Homostius.

About the Placodermi, Pterichthyodes milleri placoderm

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.



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