An Ammonite was left for Nick Cutter in his office at the Central Metropolitan University, by his wife Helen, as a calling card, although it appeared to be dying out of the water. What happened to the Ammonite is unknown, as Cutter chose to keep Helen's reappearance a secret.
Helen left a fossilised Ammonite on Stephen Hart's grave after his funeral.
Ammonites were a group of marine cephalopods, which first appeared 400 million years ago and died out in the K-T mass extinction event 65 million years ago. They were known for their shells' spiral shape and loose resemblance to a closed ram horn.