A mysterious deep-sea creature has just helped scientists solve a long-standing evolutionary puzzle.
The vampire squid—an unusual animal that looks like a mix between an octopus and a squid—has revealed that modern octopuses actually evolved from squid-like ancestors.
This discovery comes from a major international study that decoded the vampire squid’s genome, the largest cephalopod genome ever sequenced.
The vampire squid (Vampyroteuthis sp.) lives in the dark, oxygen-poor depths of the ocean. Despite its dramatic name, it doesn’t suck blood.
Instead, it eats drifting organic debris. It has big eyes that can appear red or blue, a soft dark body, and a cloak-like membrane between its arms. In Japanese, it is called “kōmori-dako,” meaning “bat-octopus,” a name that hints at its strange mix of features.
Although scientists classify it as part of the octopus lineage, the animal also shares several physical and genetic traits with squids and cuttlefish, making its evolutionary identity unclear.
To solve this mystery, researchers from the University of Vienna, Japan’s National Institute of Technology–Wakayama College, and Shimane University sequenced the vampire squid’s genome.
Their results, published in iScience, reveal that the animal sits at a key evolutionary crossroads.
More than 300 million years ago, cephalopods split into two major branches: the ten-armed group that includes squids and cuttlefish, and the eight-armed group that includes octopuses and the vampire squid.
Even though the vampire squid has eight arms like an octopus, its genome tells a more complicated story.
At over 11 billion base pairs—four times larger than the human genome—its chromosomes still preserve an ancient, squid-like organization. Because of this, the researchers describe it as a “genomic living fossil,” a creature whose DNA retains deep evolutionary history.
This is especially striking because modern octopus genomes look very different. Over millions of years, octopuses experienced major chromosomal fusions and rearrangements—massive reorganizations that helped shape their unique bodies, flexible arms, and intelligence. In contrast, the vampire squid kept much of the ancestral structure, giving scientists a rare window into early cephalopod evolution.
The team also compared this genome with that of the pelagic octopus Argonauta hians, also sequenced for the first time.
These comparisons show a clear pattern: the earliest coleoids had a squid-like genome, and the octopus lineage later evolved through fusion-with-mixing, an irreversible process that compressed and scrambled entire chromosomes. This restructuring likely supported major physical changes, such as the loss of external shells and the evolution of more complex arms.
Together, these findings change our understanding of cephalopod history. They suggest that chromosomal reorganization—not the invention of many new genes—was the main force behind the incredible diversity of today’s octopuses and squids.
And they reveal that the vampire squid still carries a genetic blueprint from a long-lost ancestor, offering scientists a rare glimpse into the early origins of some of the ocean’s most remarkable creatures.
