Paleontologists have identified Rinconraptor pipoae, a new genus and species of megaraptorian dinosaur, from an incomplete skeleton discovered in northern Patagonia, Argentina. The medium-sized predator lived about 83 million years ago during the Late Cretaceous Period.
The new species belongs to Megaraptoridae, a group of medium to large theropods known for their slender hind limbs, strongly curved teeth and large hand claws.
“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 fossil record of megaraptors remains rare and fragmented, so the phylogenetic relationships of this group are a subject of debate among experts.”
A megaraptor from Patagonia
The fossilized remains of Rinconraptor pipoae were discovered at Cerro Obero, about 50 kilometers (30 miles) southwest of the city of Rincón de los Sauces in Patagonia, Argentina.
“The specimen comes 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 it had more than 40 to 45 caudal vertebrae, a pattern similar to that seen in tyrannosaurs.
Méndez and his coauthors also described several additional megaraptorid bones from the same area that they could not assign to a particular species. These remains came from animals estimated to have been approximately 6 to 8.5 meters (20 to 28 feet) long.
Potential competition among predators
“The presence of medium and large megaraptors in the Cerro Obero-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 theropod fossil record of the region may indicate some degree of partitioning of the ecological niches occupied by carnivorous dinosaurs from both groups, allowing them to avoid direct competition for resources and coexist.”
“This is particularly relevant for the Cerro Obero-La Invernada area, which represents an ecosystem with high faunal biodiversity, including titanosaur sauropods, elasmosaurids and ornithopods.”
The team’s paper was published online this month in Palaeontologia Electronica.
Ariel H. Méndez et al. 2026. “Expanding dinosaur diversity in the Cerro Obero-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
