Later in the same paper, he proposed that Tyrannosauridae be defined as "all descendants of the most recent common ancestor of "Tyrannosaurus" and "Aublysodon"". He also criticized definitions previously proposed by other workers, like one proposed by Paul Sereno, that the Tyrannosauridae was "all taxa closer to "Tyrannosaurus" than to "Alectrosaurus", "Aublysodon", and "Nanotyrannus"". Holtz observed that since "Nanotyrannus" was probably a misidentified "T. rex" juvenile, Sereno's proposed definition would have the family Tyrannosauridae as a subtaxon of the genus "Tyrannosaurus". Further, his proposed definition of the subfamily Tyrannosaurinae would also be limited to "Tyrannosaurus".