An international team led by scientists from the CONICET, at the Laboratory of Comparative Anatomy and Evolution of Vertebrates (LACEV) of the Argentine Museum of Natural Sciences, discovered fossil remains of a reptile that lived about 70 million years ago in the province of Río Negro.
It is the most complete terrestrial lizard known for the Late Cretaceous in South America. A period that ended 65 million years ago with the mass extinction of three-quarters of plant and animal species, including dinosaurs (except for birds).
The discovery, published in Scientific Reports and supported by the National Geographic Society, provides key evidence to understand the evolution of reptiles in the southern hemisphere before the great extinction.
The new species: Paleoteius lakui
The fossil was found in the Allen Formation, at the Salitral Ojo de Agua site. Researchers named the species Paleoteius lakui.
- It measured just over 15 cm long.
- It had a skull ornamented with small protuberances.
- Its jaws were armed with numerous fine and uniform teeth, probably useful for capturing insects.
According to Federico Agnolín, the study’s first author, fossil remains of small animals are very scarce due to their fragility. In this case, a large part of the skeleton and skull was recovered, providing unprecedented information about the history of lizards in the southern cone.
Technology applied to the study
The analysis of the fossil was made possible by advanced techniques:
- Computed microtomography: allowed for digital reconstruction of internal anatomy with micrometric resolution.
- Three-dimensional models: facilitated anatomical and comparative study.
- High-performance computational resources: provided by the High-Performance Computing Center (CCAD) of the National University of Córdoba.
These technological advances, combined with interdisciplinary work with the National Atomic Energy Commission (CNEA), made it possible to study details such as teeth less than a millimeter and internal structures of the skull.
Evolutionary importance
The fossil record of Mesozoic lizards in the southern hemisphere is very limited: less than a dozen species, compared to more than 150 in the northern hemisphere. In this context, Paleoteius:
- Expands the fossil record in South America.
- Reveals previously unknown lineages in the region.
- Suggests that lizards were already diversified in Gondwana, the southern continental block of Pangea.
Phylogenetic analyses place Paleoteius within the Scincomorpha, a group that today includes skinks, cordylids, and xantusiids, distributed globally but with no previous fossils in South America.
The discovery of Paleoteius lakui fills a gap of millions of years in the fossil record of reptiles in Patagonia and offers new clues about the evolution of lizards before the mass extinction of the Cretaceous.
For scientists, this finding not only contributes paleontological knowledge but also positions the region as a key scenario for understanding the history of life in the southern hemisphere.
