New Amphibian Species Unearthed from La Brea Tar Pits Offers Insights into Ice Age Environments

Researchers at La Brea Tar Pits have made a fascinating discovery: an extinct amphibian species, *Spea labreae*, previously concealed within decades-old fossil collections. This find marks a significant contribution to our understanding of Ice Age ecosystems in Los Angeles, illustrating how even small creatures can shed light on past climatic conditions.

Only one other extinct Pleistocene amphibian has been recorded in North America, distinguishing the significance of this discovery. Although *S. labreae* was significantly smaller than the iconic mammoths and saber-toothed cats associated with La Brea, its fossils are vital for revealing insights into environmental transitions during the late Pleistocene era.

The research detailing this species is published in the Journal of Vertebrate Paleontology, highlighting ongoing findings emerging from the Samuel Oschin Global Center for Ice Age Research at the La Brea Tar Pits—hub for fossil discoveries.

Discovering Hidden Treasures

Dr. Alberto Cruz, the study's lead author, initially aimed to explore the underexamined collections of reptiles and amphibians at La Brea while working as a Postdoctoral Fellow. Originally focused on paleoecology rather than taxonomy, Cruz observed unique features in specimens that indicated something noteworthy. His curiosity led him to examine the bones closely, pushing him to reconsider their classification.

Though he first suspected that the peculiar bones might be a result of some pathology due to injury or disease, extensive comparisons with contemporary spadefoot toads indicated these specimens were distinct enough to represent 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,'" Cruz recounts. Remarkably, the fossils had been initially collected in the 1950s, demonstrating the untapped wealth within museum collections.

More than Just an Ice Age Curiosity

Dr. Emily Lindsey, Curator and Site Director at the research center, emphasizes that the discovery of *S. labreae* showcases the continual potential for new findings at La Brea, a site rich with paleontological data. "There's definitely more to come," she asserts, as the museum progresses through a transformative phase in its excavation and research practices.

While large Ice Age mammals capture public fascination, the study of smaller species like amphibians can yield critical data about historical climate and environmental shifts. Amphibians are particularly telling due to their limited mobility and high sensitivity to ecological changes, making them effective indicators of past climates.

"If you change the environment, you change the vegetation, the climate becomes warmer or colder, and it directly affects these animals," Cruz explains, underlining their role in reconstructing historical scenes of Los Angeles.

Challenges of Fossilization

However, the primary challenge lies in the fragility of amphibian remains, which are rarely preserved due to their delicate skeletons. This makes it extraordinarily noteworthy to uncover a new amphibian species like *S. labreae* within sites like La Brea Tar Pits, where environmental conditions favored fossilization.

Cruz meticulously studied the bones from the Tar Pits collection, which had not undergone close examination for nearly three decades. By contrasting these fossils with 80 other amphibian specimens archived in various institutions, he effectively demonstrated that what previously seemed to be an anomalous specimen was, in fact, a distinct species.

Shifts in Habitat and Climate

Intriguingly, the investigation also uncovered the first known presence of the Mexican burrowing toad, *Rhinophrynus*, in southwestern United States fossils. Nowadays, this species is found nearly 2,500 kilometers away in southern Mexico, suggesting a significant alteration in geographic distribution over millennia.

This shift, alongside the extinction of *S. labreae*, adds layers to the narrative of environmental transformation as the last Ice Age waned. Understanding how these amphibians adapted—or failed to adapt—to changing conditions educates modern researchers about potential responses of similar species to today’s climate challenges.

Materials provided by Natural History Museum of Los Angeles County. Note: Content may be edited for style and length.