Cladistic analyses of tyrannosaurid phylogeny often find "Tarbosaurus" and "Tyrannosaurus" to be sister taxa, with "Daspletosaurus" more basal than either. A close relationship between "Tarbosaurus" and "Tyrannosaurus" is supported by numerous skull features, including the pattern of sutures between certain bones, the presence of a crescent-shaped crest on the postorbital bone behind each eye, and a very deep maxilla with a noticeable downward curve on the lower edge, among others. An alternative hypothesis was presented in a 2003 study by Phil Currie and colleagues, which found weak support for "Daspletosaurus" as a basal member of a clade also including "Tarbosaurus" and "Alioramus", both from Asia, based on the absence of a bony prong connecting the nasal and lacrimal bones. "Alioramus" was found to be the closest relative of "Tarbosaurus" in this study, based on a similar pattern of stress distribution in the skull.