The La Brea Tar Pits became famous after much larger fossils of creatures, like giant mammoths and sabre-toothed tigers, were found there.
According to a study, this is the first extinct amphibian found in Los Angeles and only the second Ice Age amphibian species discovered in North America.
Dr Alberto Cruz was looking back at collections of amphibians and reptiles, when he came across the new species, but he initially thought it was a modern spadefoot toad which had been sick or injured.
He said: “This material is originally from the 1950s, but when you study it again, you can find gold in these specimens. It’s very cool.”