In a previous post about Raptorex kriegsteini I expounded upon Jack Horner’s suggestion that Raptorex is not an example of the Tyranosaur body pattern evolving before gigantic size. Now, Horner and colleagues have published the data behind their critiques in PLoS One:
The recently described small-bodied tyrannosaurid Raptorex kreigsteini is exceptional as its discovery proposes that many of the distinctive anatomical traits of derived tyrannosaurids were acquired in the Early Cretaceous, before the evolution of large body size. . .These findings are consistent with the original sale description of LH PV18 as a juvenile Tarbosaurus from the Upper Cretaceous of Mongolia. Consequently, we suggest that there is currently no evidence to support the conclusion that tyrannosaurid skeletal design first evolved in the Early Cretaceous at small body size.
Fowler DW, Woodward HN, Freedman EA, Larson PL, Horner JR, 2011 Reanalysis of “Raptorex kriegsteini”: A Juvenile Tyrannosaurid Dinosaur from Mongolia. PLoS ONE 6(6): e21376. doi:10.1371/journal.pone.0021376