Ammonite – Morocco

Ammonites are extinct marine cephalopods that belonged to the same group as today's cuttlefish, squid and boatmen. They lived from the Devonian period (about 400 million years ago) until the end of the Cretaceous period (66 million years ago), when they died out in a mass extinction along with the dinosaurs.

Characteristics of ammonites

• Spiral shell: Ammonites had characteristic coiled calcareous shells that were divided by partitions into chambers. The living animal inhabited the last, most recent, chamber, while the previously formed chambers were filled with gas or liquid, which helped with buoyancy.
• Complex internal structure: The partitions between the chambers created specific patterns (called sutures) that vary between species and help paleontologists identify them.
• Size diversity: Some species had shells that were only a few centimetres long, while others grew to over 2 metres in diameter (e.g. Parapuzosia seppenradensis).
• Ecology: Ammonites were predatory sea creatures that fed on smaller animals. They probably had tentacles like modern cephalopods, but this soft tissue is not preserved in the fossil record.

One possible cause of the ammonites' extinction was their reproduction. Like today's octopuses, squid and cuttlefish laid large numbers of eggs at a time at the end of their lives. These eggs and young ammonites probably lived in the upper layers of the ocean, where they may have been destroyed by a meteorite impact. In contrast, the boatmen that survived laid their eggs in smaller batches and deposited them on the sea floor, where they were protected from the direct effects of the event.