Patagonia fossil site unearths evidence from the end of the dinosaur age

Palaeontologists excavating a fossil site in Argentina have unearthed what might be a herd of hadrosaurs, along with the first Cretaceous mammal fossil from the region known as the Golfo San Jorge Basin.

Work continues at the promising fossil site located at the Cañadón Tomás Quarry, in Patagonia, southern Argentina, which has already revealed bones belonging to hadrosaurs (a large, duck-billed dinosaur) and two other dinosaur species, a Cretaceous snake and the upper jaw and teeth of a mammal from the same period, known as a reigitheriid.

The latter is the most significant find to date. It’s the first Cretaceous mammal of any kind found in this region in Southern Argentina. Mammals in the Cretaceous were mostly rodent-sized. 

Palaeontologist Matthew Lamanna, principal dinosaur researcher at Carnegie Museum of Natural History in Pittsburgh, in the US, describes the reigitheriid find as: “one of the best fossils of its kind of mammal ever discovered,” when presenting the early findings at a meeting of the Geological Society of America.

Mammal fossils from the end of the Cretaceous can help researchers better understand the period leading up to the extinction of non-avian dinosaurs, which was followed by an expansion of mammals.

Hadrosaur fossils from the Cretaceous are also rare in the Southern Hemisphere. The fossil bones found at the site include individuals of different sizes.

“The site could capture a social group, potentially even a herd of individuals that were related to each other that were all buried together. These are the kinds of things that we’ll be investigating as we dig into the site more,” explains Lamanna.

The two other dinosaur fossils include a tooth from an abelisaurid and a claw from a noasaurid or baby abelisaurid.

The Cañadón Tomás site was initially discovered in 2020 by a palaeontological impact study conducted by the Museo de La Plata, undertaken for oil companies with an interest the region.

Further excavations at the promising fossil site are now being undertaken by team of palaeontologists from the Universidad Nacional de la Patagonia San Juan Bosco (UNPSJB), who have already unearthed several significant finds.

Argentina fossil site
Overview of the Cañadón Tomás Quarry site as of March 2023 / Credit: Kara Fikse, Carnegie Museums of Pittsburgh

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