Dasosaurus tocantinensis was about 20 meters long and lived roughly 120 million years ago. Its closest known relative inhabited what is now Spain.
About 120 million years ago, a 20-meter-long dinosaur roamed what is now northeastern Brazil, leaving behind fossils that would remain buried until modern construction exposed them. A new study in the Journal of Systematic Paleontology identifies those remains as a previously unknown species, Dasosaurus tocantinensis, discovered during work on a road-rail terminal in Davinópolis, Maranhão.
Its nearest known relative, viewed through an evolutionary lens, lived in the region that is now Spain. The findings point to more than the presence of a previously unknown dinosaur group in this part of Brazil. It also offers evidence of an ancient link between the European island chain of that period and what is now South America.
The researchers state that the ancestors of the Maranhão species likely reached South America through North Africa sometime between 140 and 120 million years ago, when these lands were still joined within the supercontinent Gondwana.
A rare giant emerges
“It’s the largest known dinosaur for Maranhão, which has other species, but not sauropods like this one; rather, it has smaller ones, such as the diplodocid Amazonsaurus maranhensis, which was about 10 meters long,” says Elver Luiz Mayer, a professor at the Federal University of the São Francisco Valley (UNIVASF) in the state of Bahia.
Mayer, whose specialty is mammals from the far more recent Quaternary period, was contacted in 2021 while he was based in São Félix do Xingu in Pará state, where he worked as a professor at the Federal University of Southern and Southeastern Pará (UNIFESSPA).
The fossils were uncovered by archaeologists who were monitoring the Davinópolis construction site as part of the environmental licensing process. At first, the material was believed to belong to megafauna mammals that may have lived alongside early humans.
“Given its depth of about eight meters, I realized that it was much older. The age of the geological formation was already known from previous research and indicated that it was material from the transition from the Lower to the Upper Cretaceous, about 120 million years ago,” says Mayer. He then contacted various specialists and formed a multidisciplinary group to study the specimen.
Following a long fossil preparation process, the analyses were carried out in Pará. The specimen was later returned to Maranhão and is now kept in São Luís, the state capital, at the State Center for Natural History and Archaeology Research, which also took part in the work.
“Because it includes tail vertebrae, a 1.5-meter femur, ribs, foot bones, and arm and leg bones, this is considered a relatively complete specimen. We believe there are more fossils from this same specimen yet to be excavated at the site,” says Max Langer, a professor at the Ribeirão Preto School of Philosophy, Sciences, and Letters at the University of São Paulo (FFCLRP-USP), who participated in the study.
Langer leads the project “Exploring the Diversity of South American Cretaceous Dinosaurs and Their Associated Faunas”, which receives support from FAPESP.
A name rooted in place
The species name is tied to Maranhão itself. “Daso” means “forest,” referring to the regional woodlands that early Portuguese colonizers described as a large tangle, or “maranhão.” “Tocantinensis,” in turn, refers to the Tocantins River, as the fossil site lies near its eastern bank.
Bone microstructure analyses led by researchers Tito Aureliano and Aline Ghilardi of the Federal University of Rio Grande do Norte (UFRN) showed a growth pattern that blends features seen in older sauropods with traits associated with titanosaurs, a group closely related to the newly described species.
The result indicates that some patterns of growth and bone remodeling appeared earlier in dinosaur evolution than previously recognized. That insight may help clarify how certain dinosaurs were able to grow to such enormous sizes.
Construction exposes fragile evidence
The discovery of Dasosaurus illustrates a central tension in paleontology. Major construction projects can damage or erase fossil records, but they can also expose layers of rock that paleontologists could not easily reach with traditional hand tools alone.
“Brazil is a tropical country with dense vegetation. Geologists and paleontologists rely heavily on human activity to excavate, expose the rocks, and reveal the fossils. If we map Brazil’s fossil sites, we’ll see highways and quarries. These projects are important for understanding our heritage. But it’s obvious that specialized monitoring and artifact recovery are necessary, which doesn’t always happen,” says Langer.
“That’s why it’s urgent to foster closer cooperation between the parties to reconcile construction projects with federal legislation on fossils and promote new discoveries while ensuring the proper preservation of our heritage,” Mayer comments.
The research group is now in discussions with the construction company about continuing excavation at the site. Additional fossils could reveal more about Dasosaurus and the broader dinosaur group to which it belonged.
Reference: “A new titanosauriform with European affinities in the Early Cretaceous of Brazil: insights on Somphospondyli phylogeny, histology and biogeography” by Elver L. Mayer, Julian C. G. Silva Junior, Leonardo R. Kerber, Bruno A. Navarro, Kamila L. N. Bandeira, Juan C. Cisneros, Eliane P. Sousa, Agostina A. Pereira, Manuel A. Medeiros, Rafael M. Lindoso, Francisco Pedro Cavalcanti Neto, Aline M. Ghilardi, Tito Aureliano, Pedro L. Godoy, Gabriel S. Ferreira and Max C. Langer, 12 February 2026, Journal of Systematic Palaeontology.
DOI: 10.1080/14772019.2025.2601579
The work received support from FAPESP in the form of a doctoral scholarship, postdoctoral fellowship, and a grant under the Young Investigator modality.
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