The asphalt seeps of Los Angeles are famous for their saber-toothed cats and dire wolves, but the newest discovery to emerge from the La Brea Tar Pits is far smaller and had been hiding in plain sight for nearly a century. Researchers have identified a previously unknown extinct toad from fossils excavated in 1929, naming it Spea labreae. It is the first extinct Ice Age amphibian ever described from the Los Angeles area and only the second known from all of North America.
A fossil overlooked for nearly a century
The discovery did not come from a fresh dig but from a museum drawer. As an account of the research explains, the key specimens were two fragments of a bone called the sacro-urostyle, which connects an amphibian’s lower spine to its hips. Both had been collected during excavations in 1929 and then filed away, unstudied, for decades because tiny bones tend to draw far less attention than the dramatic skulls and limbs of large predators.
The fossils remained anonymous until 2023, when a researcher began systematically sifting through the collection and recognized that the fragments did not match any known species. That kind of delayed breakthrough is common in paleontology: major museums hold vast backlogs of specimens gathered long ago, and new discoveries often arrive not from the field but from a careful second look at material that has been sitting on the shelf.
Identifying Spea labreae
Naming a new species requires showing that its remains differ consistently from every previously described relative. The team concluded that the toad belonged to the spadefoot group, burrowing amphibians named for the hardened, shovel-like structures on their hind feet that let them dig backward into soil. The species name labreae ties the animal to the tar pits where its bones were preserved, and the findings were published in the peer-reviewed Journal of Vertebrate Paleontology.
Because the tar pits have been trapping animals for as long as roughly 60,000 years, researchers can bracket when the toad lived to somewhere within that window. The animal is now extinct, adding a small but distinct branch to the record of Ice Age life in Southern California and demonstrating that the region’s amphibians, not just its megafauna, changed over the millennia.
Why amphibian fossils are so rare
The find carries outsized significance precisely because amphibian remains almost never survive. Frogs, toads, and salamanders have small, delicate, lightly built skeletons that tend to break apart or dissolve before they can fossilize. Their bones are also easy to overlook when they do persist, dwarfed by the robust remains of large mammals that dominate most collections. That combination is why Spea labreae is only the second extinct Ice Age amphibian identified in North America, the first being a tree frog described from Florida.
The tar pits are one of the few settings capable of preserving such fragile material. The natural asphalt that seeps to the surface acts as a sticky trap and then an oxygen-poor tomb, protecting bones from the decay and scattering that destroy fossils elsewhere. Small creatures that would leave no trace in an ordinary environment can be locked away in the tar for tens of thousands of years, which is what made the survival of a toad’s hip bone possible at all.
What a small toad reveals about a lost landscape
Modern spadefoot toads are creatures of dry, open country, spending much of their lives buried underground and emerging to breed only after heavy rains fill temporary pools. The presence of a spadefoot in Ice Age Los Angeles offers a clue about the ancient environment, hinting at seasonal wet-and-dry conditions rather than a uniformly lush or uniformly arid climate. Amphibians are sensitive to moisture and temperature, so even a single species can help scientists reconstruct the habitat that surrounded the tar pits.
Rebuilding those conditions matters for understanding how the region’s ecosystems responded as the last Ice Age ended and the climate warmed. The tar pits capture a continuous record spanning that transition, and each newly identified species, however small, adds resolution to the picture of which animals lived alongside the famous predators and how the community shifted over time.
The value of revisiting old collections
The story of Spea labreae is also a case study in the scientific payoff of preserving specimens indefinitely. The bones that revealed a new species were collected before the invention of modern imaging and analytical tools, and they waited nearly 100 years for a researcher with the interest and methods to interpret them correctly. Institutions such as the La Brea Tar Pits maintain extensive research collections precisely so that future scientists can extract discoveries no one anticipated when the material first came out of the ground.
That long game continues to pay dividends. As techniques improve and new specialists turn their attention to overlooked corners of a collection, animals that were invisible to earlier generations of researchers come into focus. The newest resident of the Ice Age record is a toad small enough to have escaped notice for a century, unearthed not from the asphalt but from a shelf, a reminder that some of paleontology’s richest deposits are the museums themselves.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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