This small ammonite defines the Concavum Ammonite Zone. This is because ammonites are ‘tools of time’ – they evolved rapidly through time and their shells became trapped in the rocks in sequence.

Horn Park Quarry is the smallest National Nature Reserve (NNR) in Britain, being just one acre or 0.32 hectares in size. It was once a working quarry but it is no longer and the remaining outcrop is protected by a fence. There is no collecting other than for scientific and educational purposes. A section of the fossil beds hasbeen stripped back and protected from the weather by a removable cover. To arrange a visit, contact the Senior Reserve Manager on 07899 731404.

Find out more about ammonites as 'tools of time' on the molluscs pages.

Common name


Scientific name

Graphoceras concavum


Molluscs > Cephalopods


Inferior Oolite

Time period

Middle Jurassic


174 million years

Where found

Horn Park Quarry

Found by

Bob Chandler


Beaminster Museum

Accession number

BM 2011-43-04