New research (paywalled):

Editor’s summary:

Cephalopods are one of the most successful marine invertebrates in modern oceans, and they have a 500-million-year-old history. However, we know very little about their evolution because soft-bodied animals rarely fossilize. Ikegami et al. developed an approach to reveal squid fossils, focusing on their beaks, the sole hard component of their bodies. They found that squids radiated rapidly after shedding their shells, reaching high levels of diversity by 100 million years ago. This finding shows both that squid body forms led to early success and that their radiation was not due to the end-Cretaceous extinction event.