Close-up of fossilised saw teeth in rock

Fossilised 'saw teeth' of the ancient ray Shizorhiza stromeri

‘Chainsaw’ fish fossil joins Museum collection

The ‘saw teeth’ in this image are helping our researchers and collaborators learn about the evolution of teeth.

They belong to the nose portion of an ancient ray relative. The largest fossil of its kind, this new addition to our collections was found in Morocco in rocks around 66 million years old.

Hundreds of ‘teeth’ line the edges of the nose, or rostrum, giving the fish’s head the appearance of a jagged chainsaw. But they are not true teeth. They are thought to be highly modified versions of tooth-like structures known as denticles that cover the bodies of sharks and some rays.

While modern sharks use denticles for more streamlined swimming, this ancient fish used its modified versions for feeding. ‘It is likely it slashed into shoals of small, soft-bodied fish and squid and sucked up the dead and injured,’ said Museum collaborator Dr Charlie Underwood, from Birkbeck University, London.

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Find out more about the unique ray fossil and what it can tell us.

Fossil fish research

Explore our research on ancient fish relatives and evolution.