Raptorex

Raptorex Temporal range: Late Cretaceous, 70 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype skeleton, Tokyo
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Tyrannosauridae
Genus:	†Raptorex Sereno et al., 2009
Species:	†R. kriegsteini
Binomial name
†Raptorex kriegsteini Sereno et al., 2009
Synonyms
Raptorex kriegstenis Paul, 2010 lapsus calami

Raptorex is a 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 raptor, "robber", and rex, "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.^[1][2]

While initially considered to have come from the Yixian Formation of China, dated to approximately 125 million years ago during the early Cretaceous period, later studies showed that such an early date for the fossil are unlikely, and given its extremely close similarity to juvenile tyrannosaurids of the late Cretaceous, it probably came from the Nemegt or similar formation. The specimen is a juvenile and many researchers now consider it to be a nomen dubium, because the changes undergone by tyrannosaurids during growth are not yet well understood, so it cannot be confidently paired with an adult skeleton (though it is extremely similar to juvenile Tarbosaurus bataar skeletons of the same size and age),^[3] but recently an argument has been made supporting its validity.^[4]