Allosaurus Jimmadseni, a 26- to 29-foot long, 4,000-pound carnivore, is a newly discovered apex dinosaur that lived in North America between 57 million and 152 million years ago. The discovery is shedding new light on evolution as this is the youngest species of Allosaurus in the fossil record.
More About the Allosaurus Group
This group is described as theropods: two-legged, three-toed species with hollow bones that lived during the Late Jurassic period. There are not a whole lot of well-preserved skeletons, and most finds tend to involve scattered remains. Here’s a picture of a jimmadseni based on two nearly complete skeletons and various fossils collected over the years.
Jimmadseni Was the Top Predator of Its Time
This ultimate beast lived in the semi-arid floodplains of North America, dominating a territory that covered what is today Wyoming, Colorado, and Utah. There was no suitable rival to threaten jimmadseni’s ecological position. The dinosaur species hunted large prey with impunity, feasting upon herbivores such as Diplodocus, Stegosaurus, and various sauropods.
For its successful hunting, the bipedal carnivore used three sharp grasping claws at the end of its arms and its 80 razor-sharp teeth. Its bulk is estimated to be roughly half of that of a T. rex, which appeared some 70 million years later.
The Specimens Today
There are two nearly complete specimens — DINO 11541 (found in Utah, 1990) and MOR 693 (found in Wyoming, 1991). It was believed that the two remains belonged to the Allosaurus fragilis species. However, new studies provide evidence that these belong to the newly described Allosaurus jimmadseni. They had a short, narrow skull, and low facial crests that protruded from horns in front of its eyes, among other unique characteristics.
Compared to fragilis, the jimmadseni species had a weak skull and a narrowed stereoscopic field of view. Therefore, it can be seen as a kind of an older model when compared to the high-tech allosaurids that followed in its evolutionary wake.