Evolution: Vampire squids have inhabited the deep sea since the Oligocene

The evolutionary ancestors of vampire squids may have adapted to deep-sea environments that were low in oxygen as early as the Oligocene period (around 23¬¬–34 million years ago), according to a paper published in Communications Biology. These findings help bridge a 120 million-year gap in the vampire squid fossil record.

The modern vampire squid (Vampyroteuthis infernalis) inhabits extreme, low-oxygen habitats in the Atlantic, Indian and Pacific Oceans. However, it is unclear how or when these squids evolved the unique traits that allow them to thrive in these deep-sea environments, especially since ancestral Mesozoic squids were known to inhabit relatively shallow water in epicontinental shelves.

Martin Košťák and colleagues identified a squid fossil (Necroteuthis hungarica) from Hungary, which was originally thought to belong to a prehistoric cuttlefish from the Oligocene period. Using advanced imaging tools, the authors noticed that the fossil shared structural and chemical similarities to modern vampire squids. They also traced the source of this fossil to a low-oxygen soil environment near present-day Budapest, suggesting that the squid had initially lived in a deep-sea, oxygen-poor habitat. The authors conclude that this fossil represents an ancestor of the modern vampire squid that had already migrated to deep-sea life by at least the Oligocene period. Furthermore, the authors propose that the formation of these oxygen-poor zones may have triggered deep-sea adaptations in the vampire squid in their earlier evolutionary history.