Calculations suggest that Siats meekerorum was at least 30 feet long, making it the third largest predator ever found in North America. But that’s a conservative estimate because the bones found were from a juvenile, and a full-grown Siats (pronounced see-atch) may have been even bigger, says paleontologist Lindsay Zanno of the North Carolina Museum of Natural Science, who discovered the species. The giant dinosaur was discovered in 2008 when Zanno and her colleague Peter Makovicky of Chicago’s Field Museum of Natural History saw fragments of black fossilized bones poking out of the hills in Utah’s Cedar Mountain Formation.