Paleontologists have discovered the fossilized lower right fang of a large proborghyenid sparassidont in the Taubate Basin in Brazil.
Right lower canine of a large proborghyenid sparassodont from the Tremembé Formation, Brazil. Scale bars – 5 mm (AE) and 20 mm (H). Image credit: Rangel etc.., two: 10.4072/rbp.2025.2.0534.
The new fossil dates back to the Deseadan age of the Oligocene epoch, between 29 and 21 million years ago.
Sample given to as-yet-unnamed member Proborhyaenidae, an extinct family of South American metatherian mammals of the order Sparassidontha.
These creatures occupied the role of carnivorous predators on the continent during the Cenozoic era.
“Sparassodonta is an extinct clade of metatherians endemic to South America that represented the main terrestrial mammalian predators on this continent during Cenozoic times,” said Dr. Caio César Rangel, a paleontologist at the Federal University of Uberlandia and the Federal University of Pernambuco, and colleagues in Brazil.
“Their evolution included two major diversification events: first in the Eocene and then in the Miocene.”
“The Oligocene is characterized by lower temperatures compared to the late Eocene and Miocene.”
“This global cooling led to significant changes in the environment, which in turn caused faunal changes in South America, including the extinction and diversification of several metatherian clades.”
Life reconstruction Thylacosmilus atroxa species of saber-toothed metatherian mammals that belonged to the sister lineage of Proborhyaenidae. Image credit: Roman Uchitel.
Paleontologists collected the new 5.73 cm (2.3 in) long specimen from the lower Tremembe Formation in the eastern state of Sao Paulo, Brazil.
“The Taubate Basin is located in the state of São Paulo in southeastern Brazil and extends from the municipalities of Cachoeira Paulista to Jacarei,” they said.
“It is approximately 150 km (93 miles) long and 10 to 20 km (6 to 12 miles) wide, in a graben between the Serra do Mar and Serra da Mantiqueira mountain ranges.”
“The Tremembé Formation is the only Late Oligocene fossil unit in Brazil that preserves mammalian fossils with a diverse fauna and autochthonous species,” they added.
“The fauna of this locality is represented by Metatheria, Chiroptera, Rodentia, Cingulata, Astrapotheria, Litopterna, Notoungulata and Pyrotheria.”
The ancient predator probably lived in a swamp-lake environment and served as an apex predator.
“The observed pattern of apparent wear on the crown of the head in dogs suggests frequent use, likely associated with the capture or active handling of adult prey,” the researchers said.
This discovery expands the geographic distribution of Proborhyaenidae and adds the second record of a member of this sparassodont family in Brazil.
“This record increases the diversity of large mammals in the Tremembe Formation,” the authors say.
“Overall, the site is an important geological and paleontological resource that provides valuable information about the final stages of the Paleogene period in tropical South America.”
The discovery is described in paper published August 2025 in the journal Brazilian Journal of Paleontology.
_____
SS Rangel etc.. 2025. “Swamp monster” of the Tremembe Formation (Taubate Basin, Brazil; Late Oligocene): description of a predatory metatherian (Sparassodonta, Proborhyaenidae). Brazilian Journal of Paleontology 28(2):e20250534; doi: 10.4072/rbp.2025.2.0534
