Fatally bitten ammonites from the Lower Calcareous Grit Formation (Upper Jurassic) of NE Yorkshire, UK

Summary Two hundred and sixty-six specimens of cardioceratid ammonites found in concretions from the Tenants’ Cliff Member of the Lower Calcareous Grit Formation (Upper Oxfordian, Upper Jurassic) at Tenants’ Cliff, near Scarborough, England, were analysed to determine the type of damage within the assemblage. Forty-five specimens were severely damaged. They consist largely of just a body chamber fragment, with small pieces of fractured shell scattered through the matrix. This type of damage is characteristic of predation by sharks or marine reptiles. Fourteen, almost complete but damaged specimens showed an indent that is either subcrescentic or V-shaped. Measurements of the position of this damage showed that the V-shaped indent was present on the body chamber of these specimens anterior to the final suture. Comparisons with other specimens from different localities and time periods, as well as sedimentological evidence and modern behavioural records, suggests that such damage was caused by squids.