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Predators at the top of a marine food chain 130 million years ago ruled with more power than any modern species, McGill research into a marine ecosystem from the Cretaceous period revealed.聽

The , published in the Zoological Journal of the Linnean Society, reconstructs the ecosystem of Colombia鈥檚 Paja Formation, and finds it was teeming with marine reptiles reaching over 10 metres in length that inhabited a seventh trophic level. 聽

Trophic levels are the layers or ranks within a food chain that describe the roles organisms play in an ecosystem based on their source of energy and nutrients. Essentially, they help define who eats whom in an ecosystem. Today鈥檚 marine trophic levels cap at six, with creatures like killer whales and great white sharks.聽

The discovery of giant marine reptile apex predators occupying a seventh trophic level underscores the Paja ecosystem鈥檚 unmatched diversity and complexity, offering a rare view into an evolutionary arms race among predators and prey.聽

In their study, McGill researchers reconstructed an ancient ecosystem network for all known animal fossils in a single geological formation in central Colombia. This network was constructed using body sizes, feeding adaptations and analogues to animals living today. They also checked their network against one of the most detailed present-day marine ecosystem networks, based on living Caribbean ecosystems, which they had used as a reference. 聽

The Mesozoic era, which included the Cretaceous period, was marked by rising sea levels and warmer climates, leading to an explosion of biodiversity in marine life. The Paja ecosystem thrived with plesiosaurs, ichthyosaurs, and abundant invertebrates, giving rise to one of history鈥檚 most intricate marine food webs.聽聽

鈥淥ur study is the first to examine these possible ecological interactions,鈥� said Dirley Cort茅s, lead author and doctoral student in the Department of Biology. 鈥淯nderstanding this complexity helps us trace how ecosystems evolve over time, shedding light on the structures that support today鈥檚 biodiversity.鈥澛�

鈥淭hese findings illuminate how marine ecosystems developed through intense trophic competition and shaped the diversity we see today,鈥� said Hans Larsson, co-author of the study and Professor in the Department of Biology.聽

This research is just the beginning, the researchers said, as few fossil ecosystems have had their food webs reconstructed. There is potential for new comparisons across time and space, advancing our understanding of ancient marine life and its impact on today鈥檚 oceans.聽

About the study聽

by Dirley Cort茅s and Hans Larsson, was published in the Zoological Journal of the Linnean Society.聽聽

The research was supported by funding from the McGill-STRI Neotropical Environment Option (NEO) and the Natural Sciences and Engineering Research Council of Canada (NSERC).聽