Top predators in prehistoric oceans would have eaten killer whales as snacks

Scientists have pieced together evidence that ancient marine reptiles once swam in what is now central Colombia, and these creatures appear to have been more formidable predators than today’s mighty killer whales. 

Their presence at an unexpectedly high level in the food chain has raised new questions about how ocean ecosystems evolve. 

Paleontologists reconstructed the lives of giant reptiles and invertebrates that flourished in a lush environment roughly 130 million years ago, and uncovered a glimpse of life that sits outside what is considered standard for our modern seas.

Marine reptiles ruled over killer whales 

Experts discovered that some of these reptiles could exceed 33 feet (10 meters) in length, hinting at a way of life that appears to have been remarkably powerful. 

According to their research, these creatures ruled the seventh level in a reconstructed Cretaceous food web, while present-day killer whales and great white sharks rarely pass the sixth. 

At the heart of these findings is work by McGill University’s Department of Biology, led by doctoral student Dirley Cortés and co-author Hans Larsson, who is a professor in the same department.

Marine reptiles reached the pinnacle

Large predators typically dominate the top ranks in any oceanic food chain. Scientists often call these ranks “trophic levels.”

Modern marine systems reach a natural limit around the sixth trophic (or feeding) level, where species like orcas hover at the pinnacle of the energy pyramid. 

“Our study is the first to examine these possible ecological interactions,” said Cortés, who is lead author on the publication.

By studying fossil evidence in the Paja Formation, the team determined that Mesozoic reptiles had apparently gone one level higher. 

These ancient animals likely feasted on anything in their path, which explains how their food web stacked up so high.

Reconstructing a lost food web

This investigation on ancient marine reptiles used body size, possible feeding tools, and comparisons with existing marine species to build a detailed framework for who ate whom in that vanished Colombian sea, where the warm climates of the Early Cretaceous allowed a surge in ocean diversity. 

The Paja Formation’s fossil record reveals predators with robust jaws and swift movement, alongside an assortment of invertebrates that thrived in trophic levels beneath them. 

Researchers drew upon modern Caribbean reef networks to cross-check their results.

By comparing these fossils to present-day communities, the study uncovered what one of the paper’s authors described as “intricate links among prehistoric animals” that pushed the boundaries of the marine hierarchy.

“Understanding this complexity helps us trace how ecosystems evolve over time,” said Cortés.

How competition shaped the seas

Marine food webs do not form overnight. Competition for resources tends to bring about new evolutionary strategies and unique feeding habits.

During parts of the Mesozoic, pressure from marine predators and their potential prey made survival an ongoing challenge. 

A known surge in shell-crushing snails and other predatory invertebrates during this era has been labeled by paleontologists as the Mesozoic Marine Revolution. 

Ancient marine reptiles from the Paja Formation existed in this tense environment of changing prey, leading them to develop massive body sizes and formidable hunting styles. 

“These findings illuminate how marine ecosystems developed through intense trophic competition and shaped the diversity we see today,” said Larsson.

Why this matters today

The close study of creatures that roamed the ocean so long ago is not just about cataloging exciting fossils. Discoveries like this tell us that life’s history is packed with surprising adaptations. 

Paleontologists see a chance to compare these ancient networks with modern ones, thus providing fresh insights into how ecosystems recover from challenges such as climate change or habitat loss. 

Researchers also note that these fossil communities remind us of how species at the top of the food chain can alter their entire environment, often making space for additional biodiversity.

A window into evolution

One important lesson from this work is that dramatic shifts in ocean biodiversity occurred long before humans entered the picture.

Marine reptiles vanished near the end of the Mesozoic, but the legacy of their top-heavy food webs is imprinted in the fossil record. 

Each puzzle piece from that record, from large jaws to specialized teeth, helps paint a more accurate picture of how Earth’s seas matured.

The high trophic levels in the Paja Formation suggest that new habitats were emerging, allowing marine reptiles to reach body sizes and predatory niches that are rarely matched in modern times.

Ancient marine reptiles and ecosystems

Researchers plan to keep building models for other fossil sites. This work may reveal whether seventh-level predators were uncommon or if there were other pockets in Earth’s history where they thrived.

In many regions, marine formations remain poorly understood, so there is every chance that the Paja Formation was not the only site containing marine reptiles with astonishing hunting powers. 

More studies may show that, over millions of years, seas can produce predators more fearsome than anything we know today.

The study is published in the Zoological Journal of the Linnean Society. 

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