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Caithness Field Club

Caithness Field Club Bulletin

A New Fossil Discovery At Achanarras Quarry
by Jack Saxon

A paper has been published in the Scottish Journal of Geology describing a new fossil of a very rare group discovered at Achanarras Quarry in Caithness.

The new fossil is a chasmataspid and is closely related to the eurypterids. These creatures resemble large aquatic scorpions and were probably top predators in the Devonian Period, some 370 million years ago. Fossil eurypterids have been known from Caithness for about two centuries, mostly fragmentary. My son Roger and I collected one from John O'Groats many years ago. In life it would have measured about a metre in length. It is now in the Royal Museum in Edinburgh. A cast of this creature can be seen in Shelleys museum in the Orcadian Stone Co., in Golspie.

The new arthropod (a name given to joint-legged creatures such as crabs and lobsters) is quite small by comparison with the monster from John O'Groats, but is much rarer.

It has been called Achanarraspis reedi, after its discoverer, John Reed of Rousay, Orkney, who sadly did not realise its significance. This is the first one ever found in the Old Red Sandstone of the Orcadian Basin. Achanarras needs no description since it is world famous for its very large number of genera and species of fossil fishes.

This new creature resembles the Lower Devonian chasmataspids from Germany and the Midland Valley of Scotland. Its Middle Devonian age makes it the youngest chasmataspid yet known and significantly extends the known range of the group.

Ref A Middle Devonian chasmataspid arthropod from Achanarras Quarry, Caithness, Scotland. Anderson, L.l., Dunlop,J.A., and Trewin,N.H. Scottish Journal of Geology, 36,(2), 151-158, 2000.

Reconstruction of
Achanarras reedi gen. et sp. nov. in dorsal view.

Appendages and some carapace details based on comparisons with other Devonian chasmataspids.



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