Newly Discovered Axolotl Fossil Unearthed in Mexico

Paleontologists Discover New Axolotl Species: Ambystoma from fossil specimens found in a rocky outcrop in Hidalgo, Mexico. The species, named Ambystoma quetzalcoatli, is closely related to existing species in the central Trans-Mexican Volcanic Belt, including the Mexican axolotl (Ambystoma mexicanum) and other endemic lake species.

The new species, Ambystoma quetzalcoatli, thrived approximately 4.2 million years ago during the late Pliocene in what is now Hidalgo.

This species marks the oldest known record of the Ambystoma genus in Mexico.

“Ambystoma, a genus established in 1838, contains salamanders native to North America,” explained paleontologists Jorge Herrera Flores and María Patricia Velasco de Leon from the Autonomous University of Mexico.

“This genus is known for its distinctive developmental biology, with some species displaying paedomorphism, where adult individuals retain juvenile characteristics.”

“Living Ambystoma species are found across North America, from southern Canada to parts of the United States and the Mexican plateau,” they added.

The Ambystoma genus comprises 38 extant species, of which 18 are native to Mexico, with 17 being endemic.

The fossil record of Ambystoma is robust, particularly in the United States, where species such as the Tiger salamander (Ambystoma tigrinum) and many extinct relatives have been documented.

Ambystoma quetzalcoatli. Image credit: Jorge A. Herrera-Flores & María Patricia Velasco-de León.” width=”580″ height=”868″ srcset=”https://cdn.sci.news/images/2026/06/image_14811_2-Ambystoma-quetzalcoatli.jpg 580w, https://cdn.sci.news/images/2026/06/image_14811_2-Ambystoma-quetzalcoatli-200×300.jpg 200w” sizes=”(max-width: 580px) 100vw, 580px”/>

Subadult skeleton of Ambystoma quetzalcoatli. Image credit: Jorge A. Herrera-Flores & María Patricia Velasco-de León.

The research team examined several salamander fossils collected from the Sanctorum Fossil Site in the Santa Maria Amajac region.

By comparing these fossils to various Mexican relatives, they confirmed the discovery of a new species: Ambystoma quetzalcoatli.

This species exhibits a unique combination of skeletal features absent in living relatives, including:

• A distinctive V-shaped opening on the anterior surface of the premaxilla.
• A persistent gap in the top of the skull across different developmental stages, related to paedomorphism.
• An unusually shaped parasphenoid bone at the base of the skull.

“The integration of these morphological traits supports the classification of Ambystoma quetzalcoatli as a distinct species,” the researchers stated.

The discovery of Ambystoma quetzalcoatli enriches our understanding of the biodiversity of the ancient Lake Amajac system.

This region has yielded numerous unique fossil species, including extinct oaks, beetles, diatoms, and goodaid fishes.

The scientists propose that geographic isolation due to the surrounding mountains may have fostered the evolution of these unique species.

“The fossil description of this new Ambystoma species underscores the morphological diversity within Ambystomatidae, particularly throughout the evolutionary history of Mexican species,” they concluded.

“Moreover, the Santa María Amajac area is crucial for understanding the development of Mexico’s modern megadiverse fauna, increasing the chances for further discoveries.”

The research team published their findings in the online journal Old Trogia Electronica in May 2026. Read their paper here.

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Jorge A. Herrera Flores and Maria Patricia Velasco de Leon. 2026. Ambystoma quetzalcoatli: A new axolotl fossil species (Caudata: Ambystomatidae) from the Pliocene in Santa Maria Amajac, Hidalgo, Mexico. Old Trogia Electronica 29 (2): a19; doi: 10.26879/1644