A new species of Ice Age toad discovered at La Brea Tar Pits: The spadefoot toad Spea labreae
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For the first time, researchers have discovered a new species of extinct amphibian from Ice Age Los Angeles at La Brea Tar Pits: a spadefoot toad they have named Spea labreae. Only one other extinct Pleistocene amphibian from North America has ever been found (a tree frog from Florida).
While the toad may be 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.
The study's lead author, 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, where he remains a research associate while working full time as a researcher for Mexico's SECIHTI-Centro de Investigación Paleontológica Quinametzin (CIPAQ), Instituto Nacional de Antropología e Historia (INAH).
"I'm really more of a paleoecologist and paleogeographer, not a taxonomist," Cruz says. He first noticed the distinctive features that separate S. labreae from known spadefoot toads while reviewing the Tar Pits' collection of reptiles and amphibians.
His first thought on seeing the new species 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 spadefoot toads left no doubt.
"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."
"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."
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 make amphibians excellent climate proxies, whose presence or absence can help scientists discern changes in climate on a smaller scale.
"If you change the environment, you change the vegetation, the climate is warmer or colder, it affects these animals directly," Cruz says.
Due to their fragile skeletons, amphibians like frogs, toads and salamanders rarely make it into the fossil record 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 lead researchers like Cruz to suspect that there are many more extinct amphibians and reptiles whose remains were too delicate to make it into the fossil record.
To identify the new species, 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, 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.
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Co-authors Dr. Alberto Cruz (right) and Dr. Emily Lindsey at the Talara asphaltic site in Piura, Peru, looking for more amphibians, reptiles, and other climate-sensitive microvertebrates. Credit: Tyler Hayden -
An iNaturalist observation of the Mexican burrowing toad, Rhinophrynidae dorsalis, recorded in Costa Rica. Though now known to have inhabited Los Angeles during the last Ice Age, the closest modern populations are found in southern Mexico. Credit: Curtis Eckerman -
A nearly complete sacro-urostyle of a possibly juvenile individual of Spea labrae. Credit: Dr. Alberto Cruz -
Lead author Dr. Alberto Cruz in the field at the Talara asphaltic site in Piura, Peru. As a researcher with the Instituto Nacional de Antropologia y Historia in Mexico City, Dr. Cruznow leads research on the microvertebrate communities associated with the Santa Lucia Quinametzin mammoth site. Credit: Tyler Hayden
Along with the newly described species, the study identifies 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 their nearest populations are nearly 2,500 kilometers (1,550 miles) away in southern Mexico.
This significant range shift, along with the extinction of S. labreae, further illuminates the multifaceted story of environmental change at the end of the last ice age and helps us understand how they might cope with today's human-caused climate change.
Publication details
A new extinct Pleistocene species of spadefoot toad and comments on the paleoecology and paleobiogeography of anurans from rancho La Brea, Q1 California, Journal of Vertebrate Paleontology (2026). DOI: 10.1080/02724634.2026.2689465
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Citation: A new species of Ice Age toad discovered at La Brea Tar Pits: The spadefoot toad Spea labreae (2026, August 5) retrieved 5 August 2026 from https://phys.org/news/2026-08-species-ice-age-toad-la.html
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