Deep in the mountains of Hidalgo, Mexico, about 100 kilometers north of Mexico City, paleontologists have uncovered the fossilized remains of an ancient relative of one of the world's most remarkable living animals—the famous Mexican axolotl. The discovery, announced by researchers at the National Autonomous University of Mexico, reveals a new species they've named Ambystoma quetzalcoatli, after the Aztec feathered serpent deity Quetzalcóatl, and it marks a milestone in scientific understanding of how some of Earth's most adaptive creatures evolved.
The Mexican axolotl, known to the world as a beloved laboratory specimen and aquarium curiosity, is famous for its perpetually youthful appearance—it retains juvenile features throughout its adult life and possesses the extraordinary ability to regenerate lost limbs and tails. Now, thanks to fossils recovered from ancient lake sediments dating to the Pliocene period, scientists can trace this remarkable lineage back millions of years. What makes this discovery especially significant is that these are the first complete and articulated fossil specimens of an axolotl ever found, a rarity given how fragile the thin bones of these salamanders are.
Researcher Jorge A. Herrera-Flores and his team at the National Autonomous University of Mexico carefully analyzed multiple specimens using computed tomography imaging and compared them against modern Mexican salamander species. The fossils from Hidalgo revealed creatures that, like their living descendants, were neotenic—meaning they retained juvenile characteristics into adulthood. But their skull structure was distinctly different from other ambystomatid salamanders, unique enough to warrant naming an entirely new species. The geological age and location also supported the classification, and the findings have been published in the journal Palaeontologia Electronica.
This discovery matters because it provides the first fossil salamander species ever named from Mexico and the oldest known record for the country. Even more broadly, it illuminates how the early axolotl lineage spread and evolved, particularly among species that now inhabit the Trans-Mexican Volcanic Belt, a region of extraordinary biological richness.
The significance extends far beyond a single species. Mexico stands as one of the world's most biodiverse nations, and this fossil find is a window into just how deep that biodiversity runs. The Santa María Amajac site where Ambystoma quetzalcoatli was found has yielded far more than salamanders. Researchers have also uncovered fossil plants, insects, freshwater fishes, frogs, and snakes, painting a vivid portrait of an ancient ecosystem that thrived in what was once a pristine lake. Additional research suggests that two frog species shared this landscape with the fossil axolotl—a finding that researchers are preparing to publish.
For scientists studying amphibian evolution, this find opens new doors. While fossils of ambystomatid salamanders have been discovered in Canada, the United States, and Mexico over the years, none were as complete or well-preserved as these specimens from Hidalgo. The discovery underscores a broader truth: the natural wonders we see in Mexico today have roots stretching back millions of years, and there is far more to learn about how they came to be.