Raptorex Raptorex Raptorex is a dubious genus of tyrannosaurid dinosaur. Its fossil remains consist of a single juvenile specimen probably uncovered in Mongolia, or possibly northeastern China. The type species is "R. kriegsteini", described in 2009 by Sereno and colleagues. The genus name is derived from Latin ', "robber", and ', "king". The specific name honours Roman Kriegstein, a survivor of the Holocaust, whose son Henry Kriegstein donated the specimen to the University of Chicago for scientific study. While initially considered to have come from the Yixian Formation of China, dated to approximately 125 million years ago during the early Cretaceous
Tyrannosaurus died young, but attributes their short life spans to the dangerous lives they lived. As the number of known specimens increased, scientists began to analyze the variation between individuals and discovered what appeared to be two distinct body types, or "morphs", similar to some other theropod species. As one of these morphs was more solidly built, it was termed the 'robust' morph while the other was termed ''. Several morphological differences associated with the two morphs were used to analyze sexual dimorphism in "Tyrannosaurus rex", with the 'robust' morph usually suggested to be female. For example, the pelvis of several