A 97-Year-Old Museum Fossil Reveals LA's First Extinct Ice Age Toad

Researchers have identified the first extinct Ice Age amphibian from Los Angeles in the La Brea Tar Pits: the spadefoot toad Spea labreae. Two tiny bone fragments excavated in 1929 and ignored until 2023 double the number of known Ice Age amphibians from North America. A companion find of the Mexican burrowing toad hints at a wetter prehistoric Los Angeles.

Key Takeaways

Researchers have identified the first extinct Ice Age amphibian from Los Angeles in the La Brea Tar Pits: the spadefoot toad Spea labreae.
Two tiny bone fragments excavated in 1929 and ignored until 2023 double the number of known Ice Age amphibians from North America.
A companion find of the Mexican burrowing toad hints at a wetter prehistoric Los Angeles.

AI synthesis3 sources6

In the famous La Brea Tar Pits in the heart of Los Angeles, researchers have identified the city's first extinct Ice Age amphibian — a spadefoot toad named after the tar pits themselves: Spea labreae. The study, published in the Journal of Vertebrate Paleontology, doubles the number of extinct Ice Age amphibians known from North America.

The story begins in 1929: early excavations recovered two tiny fragments, each about a centimeter long, of the sacro-urostyle — the bone connecting the lower spine to the hips. Small fossils were long overlooked, and the pieces sat unstudied for decades. It was only in 2023 that paleontologist Dr. J. Alberto Cruz sifted through the collection and realized the bones matched no known species. The axe-shaped structure was far smaller than in any other species.

'I'm more like a paleoecologist, not a taxonomist. It is my first new species. For me, it's very exciting,' said Cruz, a research associate at La Brea Tar Pits and a researcher at Mexico's Quinametzin Paleontological Research Center. The fossil cannot be precisely dated without destroying it, but the tar pits have been active for about 60,000 years — the toad lived sometime within that window.

In the same collection, Cruz also found bones of the Mexican burrowing toad, whose nearest living populations today are about 2,500 kilometers away in southern Mexico. That suggests prehistoric Los Angeles was far wetter — a clue with modern conservation relevance.

'We've now doubled the number of known extinct ice age amphibians from North America, and so that's a pretty big finding,' said co-author Dr. Emily Lindsey. Because amphibians rarely wander far and depend on water, their fossils are valuable climate witnesses — a 'time machine' view of the past that can inform predictions about the future.