Scientists have identified new fossil species of sea urchin in Mexico

Researchers in The Zaragoza School of Advanced Studies (FES Zaragoza) at the National Autonomous University of Mexico (UNAM) has identified a new fossil species of sea urchin in the state of Hidalgo.

His name Ambystoma quetzalcoatliIt is the first fossil salamander species to be officially described in Mexico and the oldest known record of the genus. Malignant tumor It has been documented in the country. According to the researchers, this discovery provides an important new piece of the puzzle for understanding the origin and evolution of the biodiversity that characterizes the modern Mexican fauna.

The fossils were discovered in the municipality of Atotonilco el Grande, in Hidalgo, an area that was once home to an extensive system of freshwater lakes covering an area of ​​approximately 85 square kilometres. The lakes were likely formed when the course of the Amagak River was temporarily closed. This temperate, subhumid environment has produced fossils of many plants, diatoms, gastropods, shellfish, beetles, and fish. However, to date, amphibian remains recovered from the site have not been formally studied or described.

The researchers examined dozens of fossil salamander specimens collected in the early 2000s by the FES Zaragoza Paleobotany Research Group. Many of the fossils are extremely well preserved, with complete and detailed skeletons that allowed detailed anatomical analysis and careful assessment of their morphology.

The remains were initially identified as belonging to a species of the genus Malignant tumorthe group that includes modern sea urchins. However, a team led by researchers Jorge Herrera Flores and María Patricia Velasco de León has reexamined the material using modern techniques, including computed tomography (CT) scans and detailed anatomical comparisons with living species, to more accurately determine its identity.

Their analysis revealed that the fossils collected nearly three decades ago belong to an entirely new species, distinguished from modern sea urchins by several important anatomical differences.

According to the study, published in the journal Palaeontologia Electronica, the fossils display distinctive skull and skeletal features not found in living species. Among the most notable are an elongated opening in the upper part of the skull, a palate of different structure, differences in the arrangement of several cranial bones, and the presence of 17 stem vertebrae. This last characteristic is particularly important, as modern sea urchins have 16 or fewer trunk vertebrae.

To identify the fossils, the researchers compared them to 13 living organisms Malignant tumor species, including several endemic to Mexico, such as the sea urchin Xochimilco (Ambystoma mexicana), as well as tiger salamanders from Mexico and the United States. They relied on 3D imaging and CT scans available through international scientific groups.

Fossil images of a newly described sea urchin species Ambystoma quetzalcoatli In Mexico.

Cortezia UNAM/Jorge Herrera Flores