One of the joys of paleontology is finding a bonus fossil. Sometimes it takes the form of an unexpected animal showing up beneath, or associated with, another – like a turtle preserved under an ankylosaur, or a hidden mammal skull in a block of fish. But other times bonus fossils don’t just tell us about preservation, but life. For example, a salamander that was a Cretaceous frog’s last meal.
Lida Xing, Kecheng Niu, and Susan Evans recently described the fossil. The entwined amphibians were part of the famously well-preserved Jehol Biota in China’s Early Cretaceous rock. The frog appears to be a known genus called Genibatrachus, and coiled inside its gut is most of a salamander skeleton identified as Nuominerpeton.
Previously, the researchers write, experts thought that the frogs of the Jehol Biota mostly ate insects and worms. But this fossil indicates that Genibatrachus was like modern frogs – it ate whatever it could catch and stuff into its mouth. Such was the fate of the poor salamander, the completeness and articulation of its bones indicating that the amphibian was swallowed whole. “Predator and prey were of comparable size,” the paleontologists note, “and although the salamander was more gracile in its build, there must have been a struggle.”
What happened next is lost to the rock record. It’s not clear whether the frog bit off more than it could chew or befell some other fate. Either way, the amphibian was soon buried, the salamander preserved inside.
On the surface, a find like this might seem somewhat mundane. (It didn’t make headlines quite like the recent announcement of a new lizard species found inside the gut of a feathered dinosaur, for example.) But let’s flip that around. Prehistoric time is often characterized as endless eras of bizarre monsters. It’s easy for Mesozoic life to be cast as gigantic, monstrous, and strange. Look for it and you’re sure to find it, but discoveries like this one offer a connection between our time and the past. There have been some consistent interactions through deep time, allowing us to look back and see the past with moments of clarity. A sad end for a salamander brings us closer to the Cretaceous.