Paleontologists have identified Rinconraptor pipoae, a new genus and species of megaraptorian dinosaur, from an incomplete skeleton discovered in northern Patagonia, Argentina. The predator lived about 83 million years ago during the Late Cretaceous and was approximately 7 meters (23 feet) long.
A new megaraptorian
The newly described species belongs to Megaraptoridae, a group of medium-sized to large theropods known for their slender hind legs, strongly curved teeth and large claws on their hands.
“Megaraptoridae was recognized a decade ago and consists of medium to large theropods with several distinguishing features, including strongly curved teeth with a figure-eight profile, long and slender hindlimb bones, pneumatic cranial and vertebral elements, and large grooved hand claws,” said CONICET paleontologist Ariel Hernán Méndez and his colleagues.
“Megaraptoran fossils have been recorded not only in Argentina, but also in Brazil, Australia, Thailand and Japan.”
The group’s fossil record remains rare and fragmented, and its evolutionary relationships are still debated among experts, the researchers said.
Fossils from Patagonia
Fossil remains of Rinconraptor pipoae were discovered at Cerro Overo, about 50 kilometers (30 miles) southwest of the city of Rincón de los Sauces in Patagonia, Argentina.
The specimen came from the Bajo de la Carpa Formation, an integral unit of the Río Colorado Subgroup within the Upper Cretaceous Neuquén Group of the Neuquén Basin, the paleontologists said.
“Across the basin, this formation records a variety of paleoenvironments influenced by aeolian and fluvial depositional systems.”
The main specimen consists of 10 caudal vertebrae, part of the lower tail, the lower end of the left humerus and the upper end of the right tibia. The tibia remained embedded in the rock, while the other bones were scattered across the surface within an area of about 4 square meters (43 square feet).
By comparing the vertebrae with those of better-known relatives, the researchers estimated that Rinconraptor pipoae was approximately 7 meters (23 feet) long. They also estimated that its tail contained about 40 to 45 vertebrae, a pattern similar to that seen in Tyrannosaurus.
Méndez and his co-authors also described several additional megaraptorid bones from the same area that could not be assigned to a specific species. These animals were estimated to have been approximately 6 to 8.5 meters (20 to 28 feet) long.
Coexisting predators
“The presence of medium and large megaraptors in the Cerro Overo-La Invernada region during the Santonian is consistent with the record of medium and large abelisaurids,” the scientists said.
“The presence of two groups of apex predators sharing time and space may have led to competition for resources.”
However, the region’s theropod fossil record may indicate some degree of ecological niche partitioning among the carnivorous dinosaurs, allowing them to avoid direct competition and coexist, the researchers said.
“This is particularly relevant for the Cerro Overo-La Invernada area, which represents an ecosystem with high faunal biodiversity, including titanosaur sauropods, elasmosaurids and ornithopods.”
The team’s paper was published this month in the online journal Palaeontologia Electronica.
Ariel H. Méndez et al. 2026. “Expanding dinosaur diversity in the Cerro Overo-La Invernada region (Santonian Bajo de la Carpa Formation), northern Patagonia: description of new species and additional megaraptorian remains.” Palaeontologia Electronica 29 (3): a41. doi: 10.26879/1738.
Source: www.sci.news