A sketch of the giant octopus. Yohei Utsuki/Department of Earth and Planetary Sciences, Hokkaido University hide caption

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Yohei Utsuki/Department of Earth and Planetary Sciences, Hokkaido University

A hundred million years ago during the late Cretaceous period, the oceans were filled with giant predators, prowling for their next meal. There was the mosasaur — a giant toothy marine reptile (and a surprise hero in Jurassic World). There were large sharks.

And now, in the journal Science , researchers present evidence for ancient colossal octopuses — what they believe are the largest invertebrates ever described. Using innovative fossil reconstruction techniques, the researchers revealed remnants of two extinct species locked inside large rocks.…