Meet Spea labreae, a New Species of Ice Age Toad Discovered at La Brea Tar Pits
The first new extinct toad species and the first description of the Mexican burrowing toad at the Tar Pits help us understand the impacts of climate change on species distributions, past, present, and future.
Published August 5, 2026
Dr. Alberto Cruz wasn’t looking for new species when he began his review of the Tar Pits’ understudied collections of amphibians and reptiles as a Postdoctoral Fellow working at La Brea Tar Pits.
“I'm really more of a paleoecologist, paleobiogeographer, not a taxonomist,” says Dr. Cruz, but he still noticed something different about an incomplete toad bone. It was definitely a spadefoot toad, but it had distinctive features separating it from every known spadefoot. His first thought was that the specimen had been sick or injured during its life, an example of paleopathology, rather than a new species. However, further comparisons to modern spade-foot toads left no doubt: he had the first new species of extinct amphibian from Ice Age Los Angeles at La Brea Tar Pits: a spadefoot toad which he and co-author Dr. Emily Lindsey named Spea labreae.
“I reviewed and reviewed a lot of specimens until I was convinced. I thought, ‘Oh my gosh, this is a new species’. This material is originally from the 1950s, but when you study it again, you can find gold in these specimens. It's very cool,” says Cruz, who remains a Tar Pits Research Associate while working full-time as Researcher for Mexico’s SECIHTI-Centro de Investigacion Paleontologica Quinametzin (CIPAQ), Instituto Nacional de Antropología e Historia (INAH).
“It’s a great example of how we’re still finding new things at La Brea Tar Pits, even after a century of ongoing excavation and research,” says Dr. Emily Lindsey, Curator and Excavation Site Director at the Samuel Oschin Center for Global Ice Age Research at La Brea Tar Pits. “There’s definitely more to come.”
Only one other extinct Pleistocene amphibian from North America has ever been found (a tree frog from Florida). While much smaller than the mammoths and saber-toothed cats that made the Tar Pits famous, this discovery has a big impact on our understanding of the climate at the end of the last ice age. Described in the Journal of Vertebrate Paleontology, S. labreae spotlights the ongoing daily discoveries at the Samuel Oschin Global Center for Ice Age Research at La Brea Tar Pits as the iconic museum begins a historic transformation.
Ancient Climate Through the Lens of Amphibians
While the iconic large mammals often grab headlines and capture our imagination, the small reptiles and amphibians Cruz studies can tell scientists much more about ancient climate and environmental change.
Amphibians don’t travel very far within their lifetimes and are extremely sensitive to environmental conditions. This limited movement and high sensitivity makes amphibians excellent climate proxies, whose presence or absence can help scientists discern changes in climate at a smaller scale.
“If you change the environment, you change the vegetation, the climate is warmer or colder, it affects these animals directly,” says Cruz.
Due to their fragile skeletons, amphibians like frogs, toads, and salamanders rarely make it into fossil records outside of asphaltic sites like the Tar Pits. The discovery of a new species—particularly a small amphibian like S. labreae—is an extraordinary find at the Tar Pits.
Their fragility and sensitivity to environmental changes also make researchers like Dr. Cruz suspect that there are many more extinct amphibians and reptiles whose remains were too delicate to make it into the fossil record.
Courtesy of La Brea Tar Pits
To identify the new species, Dr. Cruz examined the bones of Tar Pits amphibians, a collection that had not been carefully assessed in nearly 30 years. Making detailed observations of their shape and size. Dr. Cruz compared Tar Pits amphibians to 80 specimens at the Herpetology Collections at the Natural History Museum of Los Angeles County and the Museum of Vertebrate Zoology at the University of California, Berkeley.
Along with the newly described species, the co-authors identified the first record of the Mexican burrowing toad, Rhinophrynus, from the southwestern United States. These living toads are no longer found in modern Los Angeles, and in fact, their closest populations are almost 2,500 km away in southern Mexico. Taken along with the extinction of S. labreae, this major shift in range deepens our understanding of environmental change at the end of the last Ice Age. Understanding how they responded in the Pleistocene could be vital to understanding how amphibians will deal with today's human-caused climate change, and help us better plan for their conservation.
