Scientists have identified a previously unknown extinct spadefoot toad, named Spea labreae, from fossils recovered at the La Brea Tar Pits. This marks the first extinct amphibian discovered in Los Angeles and is only the second Ice Age amphibian species found in North America, according to a study published in the Journal of Vertebrate Paleontology.
The fossil specimen, an incomplete sacro-urostyle bone that forms the base of the spine connecting to the hips, was originally excavated from Rancho La Brea in 1929. It remained largely unstudied until lead author Jose Alberto Cruz examined it more closely. Cruz initially believed the bones belonged to a known spadefoot species, but closer inspection revealed it to be a distinct, unidentified species.
"Oh my god, this is a new species that is in a drawer," Cruz stated. "And now it's in the light to the world."
The newly identified amphibian was found to be slightly larger than modern spadefoot toads. Researchers named the species Spea labreae in honor of the famous fossil site and the museum staff who contributed to the discovery.
Amphibian fossils are considered valuable indicators of ancient environments because frogs and toads are highly sensitive to climatic and water conditions. Unlike birds, they cannot easily migrate when conditions become unfavorable. This sensitivity makes Spea labreae a significant clue for understanding Ice Age Los Angeles.
Co-author Emily Lindsey, a vertebrate paleontologist at the La Brea Tar Pits, noted that the toad's presence suggests Ice Age Los Angeles was considerably colder and wetter than it is today. "If we're trying to understand what Los Angeles looked like during the Ice Age, these are some of our best clues that can give us information about that," Lindsey said.
The research team also uncovered the first evidence that the Mexican burrowing toad (Rhinophrynidae dorsalis) once inhabited the Los Angeles area, despite its closest modern populations now being found in southern Mexico. 
While the new species will not have its own dedicated display when the La Brea Tar Pits reopens after renovations, it will be exhibited alongside other flora and fauna that defined the Ice Age ecosystem.