Robert T. Bakker
A small but nearly complete skull of "Nanotyrannus lancensis", frequently considered to be a juvenile "T. rex", was recovered from Montana in 1942. This skull, Cleveland Museum of Natural History (CMNH) 7541, measures in length and was originally classified as a species of "Gorgosaurus" ("G. lancensis") by Charles W. Gilmore in 1946. In 1988, the specimen was re-described by Robert T. Bakker, Phil Currie, and Michael Williams, then the curator of paleontology at the Cleveland Museum of Natural History, where the original specimen was housed and is now on display. Their initial research indicated that the skull bones were fused, and that it therefore represented an adult specimen. In light of this, Bakker and colleagues assigned the skull to a new genus, named "Nanotyrannus" for its apparently small adult size. The specimen is estimated to have been around long when it died. However, a detailed analysis of the specimen by Thomas Carr in 1999 showed that the specimen was, in fact, a juvenile, leading Carr and many other paleontologists to consider it a juvenile specimen of "T. rex".