66 million years ago, an asteroid killed the non-avian dinosaurs. Perhaps less well known is that it also triggered the extinction of the ammonoids, an iconic group of extraordinarily diverse shelled cephalopods. Curiously, a far less diverse group of shelled cephalopods survived. These were the nautiloids, the ancestors of today's pearly nautilus. Why did the nautiloids survive, but the ammonoids go extinct?
Evidence from the fossil record is compatible with multiple possible explanations. For example, nautiloids had larger eggs, which might have allowed them to survive periods of low food availability. Nautiloids also had larger geographic distributions, possibly indicating greater flexibility in response to varying environmental conditions.
Over the course of my SNSF postdoc mobility stay in Oxford I am working with Dr Erin Saupe to assess statistically how well these and other hypotheses are supported by currently available fossil data. We aim to better understand which traits made ammonoids vulnerable, but nautiloids resilient, to the dramatic environmental changes post-impact. These insights might help to understand the risks that the last surviving nautiloid, the pearly nautilus, is facing from ongoing climate change.
