La Brea Tar Pits Researchers Discover New Extinct Amphibian Species

Researchers at La Brea Tar Pits have identified an extinct species of spadefoot toad, named Spea labreae, marking the first new extinct amphibian species found at this iconic fossil site. This discovery is particularly notable, as only one other extinct Pleistocene amphibian has been documented in North America, specifically a tree frog from Florida.

While small compared to the mammoths and saber-toothed cats typically associated with La Brea, fossils of S. labreae may offer critical insights into climate and environmental changes that took place at the end of the last Ice Age. The study detailing this discovery appears in the Journal of Vertebrate Paleontology, illustrating the ongoing research at the Samuel Oschin Global Center for Ice Age Research as the museum undergoes significant renovations.

Unexpected Find in an Old Collection

Lead author Dr. Alberto Cruz discovered the new species while examining the largely overlooked reptile and amphibian collections at the Tar Pits during his time as a Postdoctoral Fellow. Currently, he serves as a Research Associate at La Brea Tar Pits and is also affiliated with Mexico’s SECIHTI Centro de Investigación Paleontológica Quinametzin (CIPAQ) at the Instituto Nacional de Antropología e Historia (INAH).

“I’m really more of a paleoecologist, paleogeographer, not a taxonomist,” Dr. Cruz explained, noting the distinct characteristics that set S. labreae apart from recognized spadefoot toads. Initially, he speculated that the unusual bones represented a case of paleopathology from an injured or sick animal. It was only after detailed comparisons with modern specimens that he confirmed the bones indicated a new species.

“I reviewed and reviewed a lot of specimens until I was convinced. I thought, ‘Oh my gosh, this is a new species,’” Dr. Cruz remarked, emphasizing the potential hidden knowledge in museum collections. Dr. Emily Lindsey, Curator and Excavation Site Director at the Center, added, “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.”

Insights into Ancient Climate

While large Ice Age mammals garner the most attention, the smaller reptiles and amphibians analyzed by Dr. Cruz can yield valuable information about past climatic and environmental conditions. Amphibians are limited in their mobility and are acutely sensitive to environmental changes, making them effective indicators of historical climates. “If you change the environment, you change the vegetation, the climate is warmer or colder, it affects these animals directly,” he stated.

However, the delicate nature of amphibian skeletons complicates fossilization, leading to their scarcity in the fossil record outside of asphalt-rich sites like La Brea Tar Pits. This increases the significance of the discovery of S. labreae, as many extinct amphibian species may be absent from records entirely due to fragility of their remains.

Comparative Analysis and Further Discoveries

To confirm that the fossils represented a new species, Dr. Cruz conducted a thorough examination of bones from the La Brea collection, which had not undergone detailed study in about 30 years. He documented variations in skeletal shapes and sizes and compared the fossils with 80 specimens from the Herpetology Collections at the Natural History Museum of Los Angeles County and the Museum of Vertebrate Zoology at UC Berkeley.

This examination confirmed that the La Brea fossils belonged to a distinct species of spadefoot toad, not merely an anomalous individual from an existing species. Additionally, the research uncovered the first known record of the Mexican burrowing toad, Rhinophrynus, in the southwestern United States, revealing a previously unrecognized geographic range that now contrasts sharply with present-day distributions.

This major shift underscores a complex narrative of environmental change leading to the extinction of S. labreae. By studying how these amphibians responded to ancient climatic fluctuations, researchers hope to glean insights into how similar species might react to modern climate change driven by human activities.