Giant octopuses ruled the oceans 100 million years ago
Scientists have concluded that ancient relatives of octopuses may have been giant predators and hunted at the top of the marine food chain back in the time of the dinosaurs. This is important because the ancient oceans of this period were previously thought to be mostly the "domains" of large vertebrates rather than invertebrates.
The study was published in the journal Science. The scientists studied fossil jaws of ancient cephalopods found in rocks from Japan and Vancouver Island. These finds date from about 100 to 72 million years ago. The authors attribute them to early finned octopuses, the Cirrata group.
Details
The main argument was the jaws themselves. They retained strong signs of wear and tear: chips, cracks, scratches and polishing. According to the researchers, this means that the animals regularly and with great force crushed hard prey. That is, they were not passive deep-sea creatures, but active hunters with a powerful bite.
Based on the size of their jaws, scientists have estimated the length of the largest individuals to be somewhere between 7 and 19 metres. If these estimates are correct, some of these animals could have been comparable in length to whales and larger than many other invertebrates in Earth's history.
The authors also believe the find changes the view of when this group appeared. Their findings push the history of known finned octopuses about 15 million years deeper into the past, and the broader history of octopuses back about 5 million years.
Why it matters
The main point of the work is that it changes the picture of ancient marine ecosystems. While it was previously thought that the upper levels of the food chain in the Cretaceous oceans were largely dominated by large vertebrates, scientists now have a strong argument that invertebrates may have occupied the same role.
In addition, the study shows just how severely soft-bodied animals are underrepresented in the fossil record. Because octopuses are hardly preserved, their early history has long remained hidden. Here, it has been partially reconstructed from their jaws, one of the few hard body parts that can fossilise.
Background
There's an important caveat with this topic: in popular presentation, it's easy to confuse it with another Hokkaido University study on ancient squid, which also dates back about 100 million years and has also been seen as the dominant predators in the ocean. But in this case, it's the work on early finned octopuses and their fossilised jaws that is in question.
Source
Shin Ikegami et al, Earliest octopuses were giant top predators in Cretaceous oceans, Science (2026). An additional popular description of the findings is published in Science News.