Britannica
Sources used in this answer
When did ammonites become extinct?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
cephalopod
Blue-ringed octopus (genus Hapalochlaena).
Ammonites became extinct at the end of the Cretaceous Period, approximately 66 million years ago.12
Their demise occurred during the mass extinction event at the end of the Cretaceous, often referred to as the K–T extinction. Scientists hypothesize that this extinction was likely triggered by the impact of an asteroid or comet, which caused a global collapse of the food chain by disrupting photosynthesis and leading to a sudden decline in the plankton populations upon which these cephalopods relied.12