Description and Classification

Siats was a powerful predator, estimated to have reached lengths of around 9 to 12 meters (30 to 40 feet) and weighed up to 4 metric tons (about 4.4 short tons). The bones that scientists have found belonged to a young dinosaur, so fully grown adults could have been even larger. As a theropod, Siats walked on two strong hind legs, had a large head with sharp teeth, and shorter arms compared to its legs. It belongs to a group of dinosaurs called Megaraptora. Megaraptorans like Siats are generally considered to be neovenatorids, which are a type of allosauroid carnosaur. This means Siats was related to other large predatory dinosaurs like Allosaurus and Acrocanthosaurus. The discovery of Siats is important because it shows that these kinds of large meat-eaters were still present in North America much later than previously believed, before giant tyrannosaurs like Tyrannosaurus rex became the main top predators.

Distinguishing Features

Siats can be identified by several important characteristics:

• It was one of the largest known meat-eating dinosaurs in North America during its time, existing before large, advanced tyrannosaurs became common.
• Siats had unique features in its vertebrae (the bones that made up its spine) and hip bones that set it apart from other groups of theropod dinosaurs.
• As a megaraptoran neovenatorid, it represented a distinct family line of predators compared to the tyrannosaurs that would later rule the continent.
• Fossil evidence suggests that Siats had a relatively more slender or gracile build for such a large predator, especially when compared to the heavier build of dinosaurs like Tyrannosaurus rex.

Paleoenvironment and Diet

Siats lived in what is now Utah, in an area well-known for dinosaur fossils called the Cedar Mountain Formation. About 98 million years ago, this region was a warm and wet floodplain with many rivers, forests, and open woodlands. This green environment supported a wide variety of prehistoric animals. Siats shared its habitat with other dinosaurs, including large, long-necked sauropods such as Abydosaurus, plant-eating ornithopods like Eolambia, and various smaller theropods. Turtles and crocodiles also lived in the same ecosystem. As a top predator, Siats was at the peak of the food chain in its environment. It most likely hunted the large plant-eating dinosaurs that lived alongside it, using its large size, good speed, and sharp teeth to catch its meals.

Significance and Ongoing Research

The discovery of Siats meekerorum is very important because it helped fill a large gap in our understanding of North America’s top predators during the Cretaceous period. For a long time, scientists knew very little about the large meat-eating dinosaurs that lived in North America during a span of about 30 million years in the mid-Cretaceous. Siats shows that large carcharodontosaurian relatives like it were the dominant predators during this time, holding the top predator spot before giant tyrannosaurs evolved and took over. The existence of Siats helps scientists understand how dinosaur communities changed over millions of years and how different predators rose and fell. Ongoing research continues to explore how Siats and other megaraptorans are related to other dinosaur groups. Paleontologists are trying to determine if megaraptorans are more closely related to allosauroids (like Allosaurus) or to coelurosaurs, the group that includes famous dinosaurs like Tyrannosaurus rex and even modern birds. Future fossil discoveries of Siats or its relatives could provide more clues about its full adult size, how it looked, and its exact place in the dinosaur family tree.