Unprecedented Insight into the Food Chain: How Orcas and Sharks Would Have Evaded This Cretaceous Marine Super-Predator

In the shallow waters of the Cretaceous, a forgotten world was home to fearsome hunters, so powerful that no species alive today comes close to their fins. The largest of them, a ten-meter pliosaur, was placed by scientists at a level of predation never recorded in natural history. A place at the very top of the food pyramid, revealed by the careful analysis of a fossilized ecological network.

A monumental discovery in the sediments of Colombia

The cliffs of the Paja formation, in the Villa de Leyva region of Colombia, have long revealed their secrets with chisels. This exceptional fossil deposit, dated 130 million years ago, saw the emergence of one of the most complex marine ecosystems ever identified in the fossil record. The diversity of its ammonites, marine reptiles and invertebrates makes it a unique study area.

Thanks to an international collaboration led by McGill University, paleontologists have compiled all of the species identified on the site. This database, the most complete ever produced for this Lower Cretaceous interval, made it possible to reconstruct the dietary relationships between different species, from unicellular organisms to giant hunters. The fossils come mainly from the Arcillolitas Abigarradas member, the richest in biodiversity of the geological formation.

The research, published in the Zoological Journal of the Linnean Society, used ecological modeling software to map energy flows within this ancient marine world. By comparing this fossil map with that of current Caribbean reef ecosystems, the researchers discovered that certain Cretaceous reptiles occupied a trophic level higher than all contemporary marine predators.

Cretaceous marine super-predator rewrites the food chain

In biology, the trophic level measures an organism's position in the food chain. Killer whales, white sharks, and modern sperm whales peak around the sixth level. But within the Paja formation, a new peak has been identified: the seventh.

This new level is occupied by several species of pliosaurs, including Monquirasaurus boyacensis And
Sachicasaurus vitae. These reptiles with large skulls and paddle-shaped limbs could reach ten meters in length. Their anatomy and carnivorous diet raise them to the rank of extreme super-predators, also called hyper-apex predators. To date, no living species exceeds their position in the ecological hierarchy.

Analysis of the food web reveals that these giants fed on other predators, themselves consumers of carnivorous or omnivorous animals. This accumulation of levels indicates a very elongated food chain, which required an immense biomass at the base to maintain the whole. The Paja ecosystem is thus distinguished by its trophic intensity and its extreme complexity, with nearly 1000 interactions identified between species.

From an evolutionary perspective, this architecture is fascinating. The fact that such a network could exist suggests environmental conditions very favorable to the expansion of biodiversity, such as high temperatures, abundant resources and great ecological stability.

What this giant reveals about the evolution of ecosystems

Beyond the dietary performance of these reptiles, the discovery enriches our understanding of the dynamics of ecosystems on the scale of geological eras. This fossil network makes it possible in particular to measure the effects of the “Mesozoic Marine Revolution”, a phase of intense biological diversification which disrupted the relationships between prey and predators from the Triassic onwards.

Modeling of the Paja ecosystem shows that dietary complexity can reach heights in the absence of certain modern species, such as bony reef fish or evolved cephalopods. This observation suggests that alternative forms of ecological organization existed, carried by lineages that are now extinct. It also highlights the importance of ammonites in the role of intermediate relay, with unusual diversity and vulnerability.

According to the study, relayed by SciTechDaily, one of the major interests of this work lies in the possibility of comparing this network with those of other fossil periods. Ultimately, these comparisons could then reveal regularities in the evolution of marine food chains or reveal major ruptures linked to extinctions or climate change.

By comparing Paja's data with today's energy models, researchers are therefore beginning a re-reading of the limits of productivity and stability of marine environments. One more step towards understanding the invisible balances which, yesterday as today, shape life in the oceans.