A stunning discovery from the depths of time has emerged from Brazil's Crato Formation — a fossilised "hell ant," Vulcanidris cratensis, dating back 113 million years. This extraordinary find, recently detailed in Current Biology, is not just another ancient curiosity; it fundamentally reshapes our understanding of ant evolution and early insect predation strategies.
The new species belongs to Haidomyrmecinae, a now-extinct subfamily dubbed "hell ants" for their fierce predatory adaptations and bizarre appearance. It marks the oldest definitive record of ants known to science — predating previously known specimens preserved in amber from France and Myanmar.
The Crato Formation, where the fossil was found, is renowned for its exceptional preservation of ancient life. This limestone-rich geological formation, once a vast tropical lagoon during the Early Cretaceous, has yielded everything from ancient fish to feathered dinosaurs.
But Vulcanidris cratensis stands out because it provides the first-ever hell ant fossil preserved in rock rather than amber.
Dr. Anderson Lepeco and his team made the groundbreaking discovery while studying an expansive collection of fossil insects. The fossil’s astonishing level of detail allowed researchers to examine its anatomical features — features that point to complex hunting behaviors unlike anything seen in modern ants.
What Made "Hell Ants" Unique?
Modern ants use their mandibles (jaws) to grasp, cut, and manipulate food or enemies with side-to-side movements. Vulcanidris cratensis, however, had an entirely different system: its mandibles were vertically articulated — moving upward and downward — and worked together with a large, horn-like projection from the head.
This terrifying mechanism likely allowed hell ants to impale and trap prey between the horn and jaws, locking victims in a deadly embrace. Fossilized scenes from Myanmar amber even show hell ants grasping prey mid-bite, freezing dramatic moments of ancient predation in time.
Thus, even in the Early Cretaceous, ants had evolved highly specialized anatomical weapons to exploit their environment — challenging previous assumptions that sophisticated predatory adaptations took much longer to develop.
Prior to this find, scientists believed ants remained mostly forest-bound and localized during the Cretaceous. However, Vulcanidris cratensis suggests that ants were more widespread than previously thought. Their ability to adapt to different ecological niches — from tropical forests to coastal regions — may explain how ants became one of the most successful animal groups on Earth.
Indeed, today's ants account for 15–20% of all terrestrial animal biomass, with an estimated 20 quadrillion individual ants currently alive. It seems that the evolutionary roots of this success were already well established over 100 million years ago.
More Fascinating Facts about Hell Ants
Anatomical Marvels: Hell ants featured a wide diversity of facial "horns" and jaw modifications. Some had blade-like extensions; others had trapping mechanisms unique among all insects.
Ambush Predators: Evidence suggests hell ants hunted like trap-jaw ants today — waiting motionless and then striking with explosive speed.
Vanished Lineage: Despite their early success, hell ants did not survive the mass extinction events that wiped out the non-avian dinosaurs 66 million years ago. Their highly specialised traits may have made them less adaptable to changing environments.
Evolutionary Mystery: Why vertical-jawed ants disappeared while lateral-jawed ants flourished remains an open question. It might have been due to shifts in prey availability, competition with emerging ant species, or climatic changes.
The Crato Formation during the Early Cretaceous was a thriving ecosystem full of flowering plants, ancient insects, amphibians, and early reptiles. It was a time of tremendous evolutionary experimentation — when both dinosaurs and early mammals were diversifying, and flowering plants (angiosperms) had just begun to dominate terrestrial landscapes.
The presence of complex predators like Vulcanidris cratensis suggests intricate food webs where insects were both hunters and hunted — shaping evolutionary arms races that continue today.
Looking Ahead
The discovery of Vulcanidris cratensis opens new avenues for understanding not only the origins of ants but also broader patterns of insect evolution and extinction. Future studies of fossils from regions like the Crato Formation promise to reveal even more about how ancient ecosystems functioned — and how today's biological diversity took root in deep time.
As Dr. Lepeco and his colleagues continue their work, one thing is clear: the story of ants is much older, much more complex, and much more fascinating than we ever imagined.
Lepeco, A., & Others. (2024). A rock-preserved hell ant from the Lower Cretaceous of Brazil and the early evolution of Formicidae. Current Biology. Link to the study
Aditi Rao