A groundbreaking paleontological discovery in central Mexico has unveiled a previously unknown fossil axolotl species, providing unprecedented insight into the deep evolutionary history of these iconic amphibians. Scientists from the National Autonomous University of Mexico (UNAM) have formally described *Ambystoma quetzalcoatli*, the first fossil salamander species ever identified in Mexico, based on exceptionally preserved remains unearthed in the state of Hidalgo. This finding pushes the known presence of axolotls in the region back by millions of years, challenging previous assumptions about their origins and dispersal patterns across North America. The study, published in *Palaeontologia Electronica*, underscores how underexplored fossil sites in Mexico can dramatically reshape our understanding of biodiversity’s roots.
The fossils were recovered from the municipality of Atotonilco el Grande, an area that once featured an extensive freshwater lake system spanning roughly 85 square kilometers. These ancient lakes, formed when the Amajac River was temporarily dammed, created a temperate, subhumid environment that preserved a rich array of life, including plants, diatoms, gastropods, and fish. While amphibian remains had been collected at the site in the early 2000s by the FES Zaragoza Paleobotany Research Group, they had never undergone formal scientific scrutiny until now. The team, led by researchers Jorge Herrera Flores and María Patricia Velasco de León, recognized that these bones held the key to a major evolutionary puzzle, prompting a meticulous reexamination using modern analytical tools.
To confirm the fossils’ identity, the researchers employed computed tomography (CT) scanning and detailed anatomical comparisons with living axolotl species. Their analysis revealed that the dozen specimens, many with complete, articulated skeletons, belonged to an entirely new species distinct from modern axolotls. Key anatomical differences include an elongated opening on the top of the skull, a uniquely structured palate, variations in cranial bone arrangement, and—most notably—the presence of 17 trunk vertebrae, a count that differs from contemporary forms. These features suggest that *Ambystoma quetzalcoatli* occupied a different ecological niche and may have had distinct locomotion or feeding behaviors compared to its living relatives.
The discovery of *Ambystoma quetzalcoatli* carries profound implications for evolutionary biology and conservation. As the oldest known record of the genus *Ambystoma* in Mexico, it provides a critical calibration point for molecular clocks used to estimate divergence times among salamander lineages. This fossil evidence suggests that axolotls and their relatives have been evolving in Mexican freshwater ecosystems for far longer than previously thought, potentially influencing their remarkable regenerative abilities and neotenic traits. Conservationists note that understanding this deep history is vital for protecting modern axolotls, which are critically endangered due to habitat loss and pollution in the remaining canals of Mexico City’s Xochimilco region.
Beyond its scientific value, the naming of the species—*Ambystoma quetzalcoatli*—honors the cultural heritage of Mexico, referencing the feathered serpent deity Quetzalcoatl, a central figure in Mesoamerican mythology. This choice highlights the intersection of paleontology and indigenous history, reminding us that the landscapes of modern Mexico have long been shaped by both natural and human narratives. The research team plans to continue excavating the Hidalgo site, hoping to uncover additional fossils that could further illuminate the evolutionary trajectory of these enigmatic amphibians. For now, this discovery stands as a testament to the power of revisiting old collections with new technology, revealing secrets that have lain dormant for millions of years.