Paleontologists have discovered a previously unknown Ice Age spadefoot toad species at the La Brea Tar Pits, one of the world’s richest Pleistocene fossil sites. The finding adds a rare amphibian to a fossil record best known for mammoths, saber-toothed cats and dire wolves, while offering new clues about ancient California’s climate and ecosystems.
Reconstruction of Spea labreae (center and right) at the La Brea Tar Pits compared with Spea hammondii (left), the species currently found in the area, and the Mexican burrowing toad (bottom). Image credit: Arturo Dávalos.
Named Spea labreae, the extinct species is only the second Ice Age amphibian identified in North America. The only other known example is a fossil tree frog discovered in Florida.
“Because amphibians have fragile skeletons, frogs, toads and salamanders rarely enter the fossil record outside asphaltic sites such as the La Brea Tar Pits,” said paleontologists Dr. Alberto Cruz and Dr. Emily Lindsey.
“The discovery of a new amphibian species is an extraordinary find at the Tar Pits.”
The Spea labreae specimens were first excavated during the 1950s. Their identification decades later highlights the important scientific discoveries that can still emerge from museum collections and fossil archives.
“It’s a great example of how we’re still finding new things at the La Brea Tar Pits, even after a century of excavation and research. There’s definitely more to come,” Dr. Lindsey said.
In addition to describing Spea labreae, Dr. Cruz and Dr. Lindsey identified the first evidence that the Mexican burrowing toad (Rhinophrynus dorsalis) once inhabited the southwestern United States.
The species has since disappeared from the region. Today, its nearest populations are found approximately 2,500 km (1,500 miles) away in southern Mexico.
Amphibians are especially useful indicators of past environmental conditions because they generally do not travel long distances and are highly sensitive to changes in temperature and moisture. Their presence or absence in the fossil record can therefore reveal important details about ancient climate change in California.
“When the environment changes—when vegetation changes or the climate becomes warmer or colder—it affects these animals directly,” Dr. Cruz said.
The team’s study is published in the Journal of Vertebrate Paleontology.
_____
J. Alberto Cruz & Emily L. Lindsey. A new extinct Pleistocene species of spadefoot toad and comments on the paleoecology and paleobiogeography of anurans from Rancho La Brea, California. Journal of Vertebrate Paleontology, published online August 4, 2026; doi: 10.1080/02724634.2026.2689465
Source: www.sci.news