A recent discovery off the coast of Japan has turned our understanding of the evolution of marine life in ancient times on its head. A team of paleontologists from Hokkaido University has unearthed fossil clues that had been hidden for millions of years, shedding light on the crucial role squid played in the oceans during the Cretaceous period . The research, published in the journal Science , uses innovative techniques and provides compelling data on the abundance and diversity of these animals, now considered the true rulers of the seas long before anyone imagined.
Until recently, it was believed that squid only reached their peak after the extinction of the dinosaurs . However, the results of this study demonstrate that these cephalopods were already marine protagonists some 100 million years ago , evolving and diversifying far ahead of what ancient records indicated.
Rocks with secrets: the discovery that changes everything
The starting point for this surprising discovery was a block of Upper Cretaceous rock, recovered from Japanese coastal sediments. Thanks to a digital fossil mining technique —a procedure that involves sanding the rock layer by layer and scanning its interior at high resolution—scientists discovered nearly 1.000 perfectly preserved fossilized cephalopod beaks . These beaks, similar to small, curved hooks, are the strongest part of squid and offer the best window into their past.
Among all these fossils, researchers identified at least 263 squid specimens belonging to some 40 previously unknown species. The size of some of these squid proved so imposing that they even surpassed the fish and ammonites that shared their habitat, thus changing the prevailing notion of who truly reigned supreme in the Mesozoic oceans.
The use of abrasion tomography has been key to this achievement. Thanks to it, every detail of the remains has been digitized and reconstructed in 3D without losing any information, greatly improving the accuracy of paleontological studies. This method allows for the analysis of fragile microfossils, which are virtually impossible to study using conventional cutting or dissection techniques.
Squids in marine evolutionary history
The study's findings go far beyond simply describing new species. The number and size of the squid identified indicate that these animals had already achieved significant diversification and dominated food chains much earlier than previously thought. According to the authors, these squid were not only abundant but also the top marine predators in ancient Japanese oceans, outcompeting the well-known ammonites and bony fish of that era.
The research has also detected the presence of the two main groups of squid alive today : those from coastal waters (Myopsida) and those from the open ocean (Oegopsida). This implies that the radiation and diversification of these animals began much earlier than previously thought, thus rewriting the evolutionary history of cephalopods.
One explanation for why these squid have gone unnoticed for so long lies in their soft bodies, which rarely fossilize. However, their beaks—hard structures—represent a valuable exception, allowing scientists to reconstruct their diversity and ecological role in ancient times. Until this discovery, only one ancient squid beak had been clearly identified , so this new find represents a significant advance in our understanding of these invertebrates.