The Paja Formation: An ecosystem of monsters

Roughly 130 million years ago, in an area within what is now central Colombia, the ocean was filled with a diversity of species unseen today. Within that water swam several massive apex predators that are the stuff of nightmares. These marine reptiles could reach lengths of 2 to 10 meters (about 6 to 32 feet), some with enormous mouths filled with teeth, others with relatively small heads (also filled with teeth) attached to long, snake-like necks.

These giants shared the ocean with countless smaller species, many of them predators themselves. These included ichthyosaurs—dolphin-like reptiles—as well as turtles, fish, ammonites, crabs, mollusks, sharks, and at least one species of crocodyliform.

Allowing all these creatures to thrive must have required a flourishing ecosystem at all levels. Thanks to discoveries in what’s called the Paja Formation, a treasure trove where fossils are abundantly and exquisitely preserved, researchers are now beginning to figure out how the ecosystem supported so many apex predators. And they may find hints of how it flourished so soon after a mass extinction brought the Jurassic to a close.