Genomic Clock Reveals Mid-Cretaceous Split of Squid and Cuttlefish
Whole-genome analysis places the divergence of squid and cuttlefish about 100 million years ago in the Mid‑Cretaceous. After a long period of little change, the End‑Cretaceous asteroid crisis drove these soft-bodied cephalopods into deep-water refuges, followed by rapid diversification as reefs rebuilt in shallower waters, with shell loss or reduction helping many lineages cope with ocean acidification and expanding the modern Decapodiform diversity.