Paleontologists have uncovered the fossilized lower right canine of a large proborhyaenid sparassodont in the Taubaté Basin of Brazil.
The right lower canine of a large proborhyaenid sparassodont from the Tremembé Formation, Brazil. Scale bars – 5 mm in (A-E) and 20 mm in (H). Image credit: Rangel et al., doi: 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.
The specimen is assigned to a yet-to-be-named member of the Proborhyaenidae, an extinct family of South American metatherian mammals within the order Sparassodonta.
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 presented the main terrestrial mammalian predators on this continent during Cenozoic times,” said Dr. Caio César Rangel, a paleontologist with the Universidade Federal de Uberlândia and the Universidade Federal de Pernambuco, and colleagues from Brazil.
“Their evolution included two major diversification events, firstly in the Eocene and posteriorly in the Miocene.”
“The Oligocene is characterized by lower temperatures compared to the Late Eocene and Miocene.”
“This global cooling event led to significant environmental changes, which in turn caused a faunal turnover in South America, including the extinction and diversification of several metatherian clades.”
Life reconstruction of Thylacosmilus atrox, a species of saber-toothed metatherian mammal that belonged to the sister lineage of the Proborhyaenidae. Image credit: Roman Uchytel.
The paleontologists collected the new specimen, which is 5.73 cm (2.3 inches) in length, from the lower part of the Tremembé Formation in the eastern State of São Paulo, Brazil.
“The Taubaté 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) in length and 10 to 20 km (6-12 miles) in width, in a graben between the mountain range of Serra do Mar and Serra da Mantiqueira.”
“The Tremembé Formation is the only Late Oligocene fossiliferous unit in Brazil that preserves mammal fossils, with a diverse fauna and autochthonous species,” they added.
“The fauna from this locality is represented by Metatheria, Chiroptera, Rodentia, Cingulata, Astrapotheria, Litopterna, Notoungulata, and Pyrotheria.”
The ancient predator likely lived in the swamp/lacustrine environment and occupied the role of apex predator.
“The procumbence observed in the canine associated with evident wear in the crown, suggests a frequent use probably related to the capture or active processing of prey in an adult individual,” the researchers said.
The discovery extends the geographic distribution of the Proborhyaenidae and adds a second record of a member of this sparassodont family in Brazil.
“This record increases the diversity of large mammals in the Tremembé Formation,” the authors said.
“Overall, this locality is a significant geological and paleontological resource that provides valuable insights into the final stages of the Paleogene period in intertropical South America.”
The discovery is described in a paper published in August 2025 in the journal Revista Brasileira De Paleontologia.
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C.C. Rangel et al. 2025. The ‘swamp monster’ of the Tremembé Formation (Taubaté Basin, Brazil; Late Oligocene): a description of a carnivorous metatherian (Sparassodonta, Proborhyaenidae). Revista Brasileira De Paleontologia 28 (2): e20250534; doi: 10.4072/rbp.2025.2.0534
