Canadian scientists from McGill University have pinpointed the habitat of the planet’s largest marine predators. The evidence places these giants in the Cretaceous oceans that existed about 130 million years ago in a region that would later become part of present-day Colombia. The work offers new insight into how ancient seas looked and how life organized itself there, shaping our understanding of early marine ecosystems.
Researchers studied the Paja Formation in Colombia, a fossil-rich seabed that captures a seascape teeming with marine reptiles measuring more than 10 meters in length. These colossal animals occupied a seventh trophic level in the ancient food web, a tier associated with top predators and high-energy lifestyles. By comparison, modern marine systems typically feature six trophic layers dominated by apex predators such as killer whales and large sharks. Trophic levels help explain who ate whom and how energy moved through the ancient ecosystem.
McGill scientists built an integrated network model of the long-extinct ecosystem, drawing on fossil shapes, tooth wear, bone adaptations, and similarities to living species to infer feeding strategies and ecological roles. They combined body size data with knowledge of nutritional strategies to reconstruct how energy flowed among predators, mid-level consumers, and prey living in the Paja Formation.
The Mesozoic era, including the Cretaceous period, was marked by rising sea levels and a warming climate, conditions that spurred a surge of biodiversity in marine life. This backdrop set the stage for a richly connected ocean community, where energy moved through diverse organisms from tiny invertebrates to gigantic reptiles.
The Paja ecosystem flourished with plesiosaurs, ichthyosaurs, and a wide variety of invertebrates, contributing to one of the most intricate marine food networks documented in the fossil record. The study illustrates how energy and nutrients would have circulated across multiple consumer levels, from swift swimmers to apex predators.
Scientists note that giant Cretaceous sea monsters would have posed a serious threat to today’s top predators if they could roam modern oceans. This thought experiment underscores the scale and architecture of ancient marine communities and the magnitude of life forms that inhabited them.
Paleontologists have previously described bones of what is considered the oldest marine dinosaur found in the southern hemisphere, highlighting ongoing discoveries about early marine life and its evolutionary path.