New Ice Age Toad Species Identified From La Brea Tar Pits Fossil

The La Brea Tar Pits are best known for preserving mammoths, dire wolves, giant ground sloths and saber-toothed cats. But a much smaller resident of the ancient landscape has now added a new chapter to the site’s fossil record: a previously unknown species of spadefoot toad. Researchers named the animal Spea labreae after the Los Angeles fossil site. According to Smithsonian Magazine, it is the first extinct Ice Age amphibian identified at La Brea and only the second extinct Ice Age amphibian species discovered in North America. The fossil was recovered in 1929, but its unusual appearance initially led paleoecologist J. Alberto Cruz to consider whether it might have belonged to an injured or diseased animal. Cruz and fellow researcher Emily Lindsey later compared the remains with other specimens held at La Brea, the Natural History Museum of Los Angeles County and the University of California, Berkeley’s Museum of Vertebrate Zoology. Distinctive characteristics in a fossilized sacro-urostyle—a bone at the base of the spine that connects to the hips—showed that the specimen represented a separate species. The study identifying S. labreae was published August 4 in the Journal of Vertebrate Paleontology. The toad’s precise age has not been established because determining it would require a destructive testing method. Based on other fossils found in the same tar pool, however, the researchers suspect it lived at least about 45,000 years ago, during the last Ice Age. The discovery also provides environmental clues. Amphibians generally remain close to water, while their cold-blooded biology makes them particularly dependent on surrounding conditions. The presence of the toad therefore suggests that the La Brea area once had a wetter environment and a climate capable of supporting it. Cruz and Lindsey also identified remains of a Mexican burrowing toad, which had not previously been documented at La Brea. The species survives today, but its nearest modern populations are in southern Mexico, roughly 1,500 miles from Los Angeles. That gap suggests the toad’s geographic range has changed substantially since the individual became trapped in the ancient asphalt.