An article published in the journal “Historical Biology: An International Journal of Paleobiology” describes various dinosaur fossils discovered in Idaho, USA. Those are several species belonging to the theropod (Theropoda) suborder showing a much greater diversity than was known. The fossils date back about 95 million years ago and according to the team of paleontologists who examined them also include tyrannosaur ancestors.

Paleontologist L.J. Krumenacker of the Department of Earth Sciences at Montana State University (MSU) is the lead author of this study. It concerned the fossils found in Wayan Formation, a set of rock layers that have similar characteristics and distinct from those of the adjacent layers. This is an area already known for the presence of fossils of animals and plants but the paleontological research has been limited by the lack of extensive outcrops, limited geographical extent and extreme structural deformation.

No complete skeletons were found, only isolated teeth and vertebrae. Along with them there were also eggs and eggshells. The consequence is that the estimates of these animals’ sizes were performed based in particular on their teeth.

Among the fossils examined in this research there are some previously unknown theropod from the late Cretaceous and they’re small and medium-sized tyrannosauroids (tyrannosauroidea family). The largest among them had an estimated size similar to that of a horse while the smaller ones could be the size of Labrador dogs. They’re certainly not at the same level as the famous Tyrannosaurus rex, nonetheless they were predators.

Another of the dinosaurs found could belong to the neovenatorid (neovenatoridae) family, other carnivorous dinosaurs that lived in the Cretaceous. Compared to other carnosaurs they had long and clawed arms. The Allosaurs were the main representatives of this family.

Other dinosaurs found were attributed to the dromaeosaurid (Dromaeosauridae) family. They were feathered dinosaurs that lived in the Cretaceous. The names of various genera end in “raptor” and various species are informally called with names that include “raptor” to emphasize their similarities with birds.

Some of the fossils found have yet to be identified. It’s a really difficult job because there are just a few bones but Professor David J. Varricchio of MSU, one of the study authors, pointed out its importance. Dinosaur fossils are rare in Idaho so any discovery helps to reconstruct the evolution of the various species that lived in that area.