Biostratigraphic table for Orkney indicating the range for antiarchs:

Pm Pterichthyodes milleri Ao Asterolepis orcadensis Md Microbrachius dicki 

Placoderms, antiarchs


The antiarchi look like the other placoderms but have a tail which is covered with thin but clearly visible scales. They have very peculiar pectoral appendages (like arms) instead of pectoral fins. These pectoral appendages are also armoured with bony plates and movements is made possible by a very well developed joint system, similar to the legs of lobsters or crabs.The appendages also have tiny hooks at the anterior end.

The eyes were situated on top of the head instead of on the sides as in most placoderms. Probably they spend most of the time on the bottom of the lake feeding with their tiny ventrally placed mouth on small invertebrates or scavenging.

Placoderms probably possessed lung like structures but more work needs to be done to test this hypothesis.

Pterichthyodes milleri Asterolepis orcadensis

Microbrachius dicki      Bibliography