Cienciargentina longibrachia: Argentina’s New Dinosaur with Arms Longer Than Its Entire Body!

Paleontologists have described Cienciargentina longibrachia—a bizarre new therizinosaur from Patagonia whose forelimbs are longer than its entire body, shattering every ᴀssumption about dinosaur proportions.

Discovered in 2024–2025 in the Allen Formation of Río Negro Province (~70 million years ago), the remarkably complete skeleton includes a 2.4-meter-long arm span on an animal whose snout-to-hip length is only 2.1 meters. Each arm ends in three enormous, sickle-shaped claws up to 45 cm long, sheathed in keratin. The elongated humerus, radius, and hyper-elongated metacarpals suggest these limbs were used for sweeping through dense vegetation or dramatic visual displays rather than typical herbivorous raking.

Estimated at 4.5–5 meters long and 1.2 tonnes, Cienciargentina (“Argentine science”) was named in honor of the Argentine scientific community. Lead author Dr. Leonardo Salgado and colleagues, publishing in Nature (June 2026), argue the extreme arm length represents an evolutionary extreme for therizinosaurs—pushing the limits of forelimb elongation seen in sloth-like dinosaurs. The animal likely lived in forested floodplains where its “ridiculously long arms” allowed it to reach high foliage or create intimidating threat displays against predators like Mapusaurus.

“This is the most anatomically extreme dinosaur we’ve ever found,” Salgado noted. “Nature went all-in on the arms, and the result is spectacular.”

The discovery underscores South America’s role as a cradle of bizarre dinosaur evolution right before the end-Cretaceous extinction. From the badlands of Patagonia, Cienciargentina longibrachia proves that sometimes evolution throws all caution to the wind—and the results are gloriously weird. A true scientific triumph!