The fossils prove octopuses existed at least 5 million years earlier than originally thought. Credit: Yohei Utsuki / Hokkaido University Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Around 100 million years ago, real kraken-like creatures stalked Earth’s prehistoric oceans. According to a study published today in the journal Science , some of the planet’s oldest known octopuses measured nearly 65-feet-long and ruled their underwater domains. “Our findings suggest that the earliest octopuses were gigantic predators that occupied the top of the marine food chain in the Cretaceous,” Yasuhiro Iba , a study co-author and marine paleontologist at Hokkaido University in Japan, explained in a statement , adding that they “may have surpassed the size of large marine reptiles of the same age.” Invertebrates like these are notorious for leaving little trace of their existence.…