A large orca from the Lower Pleistocene of the Southern North Sea Basin pushes back the origin of macropredatory behavior in the oceanic dolphins (Odontoceti, Delphinidae)

The evolutionary history of the biggest extant top predator of our planet, the killer whale Orcinus orca , remains poorly understood. Currently, the fossil record of the genus Orcinus includes only a single formally recognized extinct species, the small-bodied (3.5 meters) piscivorous Orcinus citoniensis from the Pliocene of Cetona, Italy. Here we describe and refer to Orcinus sp., five delphinid fossil remains from the Pleistocene of the southern North Sea, consisting of two fragmentary crania, an incomplete mandible and two atlas-axis cervical complexes. Regression analyses based on extant Orcinus orca measurements and 3D model comparisons indicate an estimated body length between 7.2 and 7.7 m, comparable to that of the largest living male killer whales. Palynological dating of the sediment of one cranial specimen supports a Gelasian (2.6–2.1 Ma) age. This large representative of the genus Orcinus displays morphological features - including large, deep, and widely separated alveoli and deeply excavated condylar fossae - indicating macroraptorial feeding abilities. Orcinus sp. represents the largest Pleistocene delphinid yet documented and provides the earliest known evidence for the emergence of macroraptorial predation within Delphinidae, substantially predating the Middle Pleistocene divergence of modern killer whale ecotypes inferred from genomic data. By demonstrating that this feeding strategy was established more than two million years ago, our results underscore both the long-term stability of apex predation in marine ecosystems and its potential vulnerability to rapid human-induced environmental change.