New North American giant theropod unveiled

Siats meekerorum was a giant carcharodontosaur that lived 98 million years ago during the Cenomanian stage (Late Cretaceous). Named after a cannibalistic monster from Ute tribal legend, Siats meekerorum was the apex predator at its time and kept smaller tyrannosaurids from taking the throne.

The specimen, discovered by Lindsay Zanno and Peter Makovicky (Chicago's Field Museum of Natural History), weighed about 4 tons and was more than 9 meters long. Although this was a big animal, the bones belonged to a juvenile. As an adult this theropod would have been 11-12 meters long and weighed more than 6 tons.

Siats belonged to Neovenatoridae (new hunters) family which is distinguished by having a short and wide scapula and ilia with many cavities. This species roamed along what now is Utah and is a relevant discovery not only because of its dimension but also because it fills a gap in that period's paleoecology since there wasn't an apex predator discovered  for that determined timespan.

                                                    by: Jorge Gonzales

For more information check: "Neovenatorid theropods are apex predators in the Late Cretaceous of North America" Nov. 22, 2013 in Nature Communications

Abstract 
Allosauroid theropods were a diverse and widespread radiation of Jurassic-Cretaceous megapredators. Achieving some of the largest body sizes among theropod dinosaurs, these colossal hunters dominated terrestrial ecosystems until a faunal turnover redefined apex predator guild occupancy during the final 20 million years of the Cretaceous. Here we describe a giant new species of allosauroid—Siats meekerorum gen. et sp. nov.—providing the first evidence for the cosmopolitan clade Neovenatoridae in North America. Siats is the youngest allosauroid yet discovered from the continent and demonstrates that the clade endured there into the Late Cretaceous. The discovery provides new evidence for ecologic sympatry of large allosauroids and small-bodied tyrannosauroids. These data support the hypothesis that extinction of Allosauroidea in terrestrial ecosystems of North America permitted ecological release of tyrannosauroids, which went on to dominate end Cretaceous food webs.