It was a cold case with hundreds of victims. For decades, scientists puzzled over a gruesome mystery: What killed hundreds of fossilized frogs found at an ancient "death trap" in Germany dating to millions of years ago? These frogs seemed to be completely healthy when they died, but researchers recently determined that the amphibians may have drowned during aggressive underwater sex.
For the new study, scientists analyzed the remains of 168 frogs found at an old mining site in the Geiseltal valley, in central Germany's Saxony-Anhalt region. The specimens were originally collected between the 1930s and 1950s, along with around 50,000 other fossils. Around half of those were vertebrates, and included horse ancestors, large crocodiles, giant snakes and ground-dwelling birds, researchers said in a statement(opens in new tab).
The fossilized frog bones date back to around 45 million years ago during the Eocene epoch; at the time, the site was a coastal swamp bordering the Palaeo-North Sea, which covered most of northern Germany. Chemical conditions within the swamp delayed the decay of dead organisms until they could be fossilized by minerals in the water, which preserved the paleontological "treasure trove" of specimens, according to the statement.
