While most of us think that the T-Rex is the biggest and meanest bully in the planet during the jurassic period, scientists have revealed that even the ferocious dino would have chickened out on seeing a much bigger predator - paleontologists have unearthed fossils of a 30-feet long dinosaur called Siats meekerorum, that could have been at the apex of the food chain 100 million years ago, or about 30 million years earlier before T-Rexes roamed the planet.

Scientists named the four-ton giant meat-eater after the cannibalistic monster lifted from the myths of the Ute Native Americans and after the name of a family donor of Chicago's Field Museum of Natural History. While similar to the looks of a T-Rex, Siats are classified as a carcharodontosaur, differentiated from the former by having three digits and a slender body. According to experts, the Siats' closest relative could be the Giganotosaurus discovered in South America.

The bones of the prehistoric animal were found during an expedition of the museum's team of experts in Utah in 2008. The scientists led by dinosaurs curator Peter Makovicky and then Field Museum fellow Lindsay Zanno excavated the scattered fossils of the Siats from a 98-million old rock in the area Cedar Mountain Formation.

"This thing is gigantic. There's simply nothing even close in this ecosystem to the size of this animal that could've been interpreted as an apex predator," said Zanno, now paleontology director at North Carolina Museum of Natural Sciences, in an interview.

The discovery of the Siats also fills a wide gap in the timeline of dinosaur existence. The feared T-Rex is said to have ruled the lands 60 million years ago, while the Acrocathosaurus, a type of carcharodontosaur, unearthed in 1950, existed 120 million years ago.

The results of the study titled "Neovenatorid theropods are apex predators in the Late Cretaceous of North America" were published in the journal Nature Communications.

"This is the first evidence that these animals existed in North America. Until a few years ago, these dinosaurs were not known from northern continents, so we thought that the dinosaurs that roamed northern continents were distinct from those that lived on southern ones due to continental drift.  As it turns out, finding closely related dinosaurs on multiple continents suggests that these animals were better able to cross barriers like spreading oceans than we previously thought," said Makovicky in a press statement.