A newly identified giant dinosaur species, *Bicharracosaurus dionidei*, discovered in Argentina, is providing new insights into the evolution of Jurassic sauropods in the Southern Hemisphere. This dinosaur measured an estimated 20 meters (65 feet) long. It exhibits a unique combination of features found in both *Diplodocus* and *Brachiosaurus* relatives.
Researchers recovered over 30 vertebrae from the neck, back, and tail, along with ribs and part of the pelvis. The bone structure indicates the remains belonged to an adult animal. It lived approximately 155 million years ago on Gondwana, the ancient southern supercontinent. Some skeletal parts resemble *Giraffatitan*, a brachiosaurid from Tanzania. Other features, particularly in the back vertebrae, are similar to *Diplodocus* and related species from North America.
Doctoral student Alexandra Reutter, the study's first author, states that phylogenetic analyses suggest *Bicharracosaurus dionidei* is related to Brachiosauridae. This would make it the first known Jurassic brachiosaurid from South America. The discovery helps fill a significant gap in the dinosaur fossil record.
Professor Oliver Rauhut of the Bavarian State Collections of Natural History (SNSB) noted that prior knowledge of Late Jurassic sauropod evolution relied heavily on findings from the Northern Hemisphere. The fossil site in Argentina's Chubut province offers crucial comparative material. This allows scientists to continuously update their understanding of these animals' evolutionary history, especially in the Southern Hemisphere.
The dinosaur's name honors local shepherd Dionide Mesa, who discovered the first fossils. The genus name, *Bicharracosaurus*, comes from a colloquial Spanish term for "big animal." The fossils were found in the Cañadón Calcáreo rock formation in Patagonia. They are now housed at the Museo Paleontológico Egidio Feruglio in Trelew, Argentina.
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