Paleontologists have unearthed the fossilized lower right canine belonging to a substantial proborhyaenid sparassodont within Brazil’s Taubaté Basin.
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.
This newly discovered fossil fragment has been dated to the Deseadan age of the Oligocene epoch, placing its origin between 29 and 21 million years prior to the present.
The specimen has been categorized under an as-yet-unnamed taxon within the Proborhyaenidae, an extinct lineage of South American metatherian mammals that constituted the order Sparassodonta.
These ancient animals served as the predominant carnivorous predators on the South American continent throughout the Cenozoic era.
“Sparassodonta represents a defunct clade of metatherians indigenous to South America, which held the position of the primary terrestrial mammalian predators on this continent during Cenozoic times,” stated Dr. Caio César Rangel, a paleontologist affiliated with the Universidade Federal de Uberlândia and the Universidade Federal de Pernambuco, alongside his Brazilian colleagues.
“Their evolutionary trajectory encompassed two significant phases of diversification: one during the Eocene and another later in the Miocene.”
“The Oligocene epoch is distinguished by comparatively cooler thermal conditions when contrasted with the Late Eocene and Miocene periods.”
“This global phenomenon of cooling precipitated substantial alterations in environmental conditions, subsequently inducing a significant faunal shift across South America, characterized by both the extinction and proliferation of various metatherian clades.”
A life reconstruction of Thylacosmilus atrox, a species of saber-toothed metatherian mammal that shares a close evolutionary relationship with the Proborhyaenidae. Image credit: Roman Uchytel.
The paleontological researchers procured the recently identified specimen, measuring 5.73 cm (2.3 inches) in length, from the basal strata of the Tremembé Formation, situated in Brazil’s eastern State of São Paulo.
“The Taubaté Basin is geographically located within the State of São Paulo in southeastern Brazil, extending across the municipalities from Cachoeira Paulista to Jacarei,” the researchers articulated.
“It spans an approximate length of 150 km (93 miles) and a width varying between 10 to 20 km (6-12 miles), existing within a graben that lies between the Serra do Mar and Serra da Mantiqueira mountain ranges.”
“The Tremembé Formation stands as the sole Late Oligocene fossiliferous deposit in Brazil that has yielded mammal fossils, revealing a rich and endemic fauna,” they further elaborated.
“The faunal assemblage recovered from this locale is comprised of representatives from Metatheria, Chiroptera, Rodentia, Cingulata, Astrapotheria, Litopterna, Notoungulata, and Pyrotheria.”
This ancient carnivore likely inhabited a swampy or lacustrine environment and occupied the ecological niche of an apex predator.
“The forward-projecting orientation observed in the canine, coupled with evident wear on its crown, implies its frequent utilization, potentially linked to the active capture or dismemberment of prey by an adult individual,” the research team commented.
This significant discovery serves to broaden the known geographical distribution of the Proborhyaenidae and marks the second documented occurrence of a member of this sparassodont family within Brazil.
“This particular find augments the recognized diversity of large mammals within the Tremembé Formation,” the authors emphasized.
“Collectively, this geological site represents a crucial paleontological resource, offering invaluable insights into the concluding phases of the Paleogene period in intertropical South America.”
The details of this paleontological revelation are presented in a publication that appeared in August 2025 in the scientific 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
