Uruguayan paleontologists have discovered a new species of eorosaur, a titanosaur, from two well-preserved coccyx bones found near the Uruguay River in the 1980s.
Mesetasaurus protector roamed what is now Uruguay between 86 million and 72 million years ago during the late Cretaceous period.
This new species is part of a group of sauropod dinosaurs known as titanosaurs. The Aeolosaurini lineage thrived across South America during the Cretaceous period’s final stage.
“Titanosaurs were the most diverse and abundant sauropod clade of the Late Cretaceous, with numerous genera identified, particularly in South America,” commented Dr. Matias Soto Nuñez from the University of Lepsidade de la Repubblica and collaborators.
“They existed by the Valanginian (137-132 million years ago), achieved enormous sizes in the Albian-Cenomanian (113-94 million years ago), and uniquely survived until the end of the Cretaceous (67 million years ago).”
“Multiple lineages, including Aeolosaurini, flourished in South America, encompassing Andesauridae, Diamantinasauridae, Saltasauridae, Rogoncosauridae, and Rhynchosauridae,” added the researcher.
“Among these, the latter clade represents a distinctive component of the latest Cretaceous fauna in South America.”
“The unique morphology of the caudal vertebrae allows for easy identification, making them viable indicators for biostratigraphy.”
The two caudal vertebrae of Mesetasaurus protector were collected in the 1980s from the Meseta de Artigas site in the Guichon Formation, located in Paysandu Department, northern Uruguay.
The specimen was found embedded in a reddish sandstone outcrop, indicating it belonged to a single individual.
“This specimen, cataloged as FC-DPV 3740A and FC-DPV 3740B, represents one of the best-preserved sauropod vertebrae discovered in Uruguay,” stated the paleontologists.
To position Mesetasaurus protector within the dinosaur family tree, researchers utilized a comprehensive phylogenetic dataset, comparing it with numerous other titanosaurs.
Their findings place this dinosaur deep within the Aeolosaurini family, alongside its relatives Aeolosaurus lionegrinus and Ardatitan Maximus from Argentina and Brazil.
This discovery suggests several lineages of giant herbivorous dinosaurs thrived in present-day Uruguay during the Late Cretaceous, rather than a single isolated population.
“Mesetasaurus protector is the second sauropod from Uruguay, belonging to a distinct lineage of titanosaurs, unlike the saltasauroids. The first is Uderartitan Celeste,” the researchers noted.
This is also the second record of an aeolosaurid in Uruguay, in addition to the latest Cretaceous Asensio Formation, featuring caudal vertebrae of Aeolosaurus.
A research paper detailing the discovery of Mesetasaurus protector was published online on July 8, 2026, in the Ameginiana journal.
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Matias Soto Nuñez and others. A new aeolosaurid (sauropod, titanosaur) discovered from the Late Cretaceous of Uruguay. Ameginiana published online on July 8, 2026. doi: 10.5710/amgh.19.06.2026.3689
Source: www.sci.news
