A golf-ball-sized blue octopus collected nearly a mile beneath the Pacific Ocean in 2015 has been formally described as a new species — and in doing so, it has forced scientists to rewrite the textbook definition of the deep-sea octopus family it belongs to.

Hidden deep beneath one of the world's most famous island chains, scientists have uncovered a tiny marine mystery unlike anything they had seen before.

The kraken — a gigantic, tentacled sea monster capable of dragging ships and sailors down into the depths — is a creature of Norwegian myth. But millions of years ago, a similar real-life animal lurked in the deep. Fossilized jaws reveal that enormous ...