Hecticoceras bonarelli ammonite fossil collected from the Jurassic Oxford Clays of Woodham, Buckinghamshire. Hecticoceras is an extinct genus of ammonite which can be found in Mid to Upper Jurassic sediments. They were nektonic carnivores which fell to the sea floor upon death. These examples were preserved within an oxygen starved deep marine shelf which gave rise to the Oxford Clay Formation. They have evolute shells and ribs however the ribs on these particular specimens have been somewhat smoothed and appear absent on some of the specimens. A typical shell measures between 2 and 3 cm in diameter. Supplied in a small plastic bag with an information label.