The first matrushka

From Austin, Texas, at a meeting of the Society of Vertebrate Paleontology

A team of German paleontologists has unearthed a fossil that preserves one creature inside another that’s nestled inside yet another, a Paleozoic version of the Russian nesting dolls known as matrushkas.

The unusual find came from material deposited about 290 million years ago in a large lake in a mountainous area of what is now southwestern Germany, says Stephanie Klug, a paleontologist at the Museum of Natural History in Berlin. All creatures in this fossilized food chain represent known species, she notes. However, this is the first time that researchers have discovered direct evidence of a three-level aquatic food chain where all members were vertebrates.

The ultimate predator in the ancient gluttonfest was a 1-meter-long freshwater shark. Just before the shark died it had evidently swallowed two larval amphibians. The lengths of their skulls suggest that each animal, when alive, was about 30 centimeters long. This discovery is the first evidence that freshwater sharks preyed on amphibians, says Klug.

What completes the trifecta, however, are the heavily digested remains of a fish found inside one of the larval amphibians. Only the body and a few pieces of the fish’s fins were preserved, but those fragments allowed the researchers to identify the species, recognize the remains as those of a juvenile, and estimate that it was about 15 cm long at dinnertime.