Tyrannosauridae

Holtz, T. R., 2001, The phylogeny and taxonomy of the Tyrannosauridae, Mesozoic Vertebrate Life, Bloomington: Indiana University Press, pp. 64-83 : 66-67

As in some previous studies ( Matthew and Brown 1922; Olshevsky et al.. 1995a, b; Currie in press), Tyrannosauridae

was found to comprise two clades: Aublysodontinae and Tyrannosaurinae . Potential phylogenetic taxonomic definitions for the clades in question might be: Tyrannosauridae , all descendants of the most recent common ancestor of Tyrannosaurus and Aublysodon ; Aublysodontinae , Aublysodon and all taxa sharing a more recent common ancestor with it than with Tyrannosaurus ; and Tyrannosaurinae , Tyrannosaurus and all taxa sharing a more recent common ancestor with it than with Aublysodon . However, these definitions must be provisional, as the type species of Aublysodon , A. mirandus , is known only from isolated premaxillary teeth, while the somewhat more complete A. molnari is known only from skull elements and may eventually prove to be a different genus. Similar problems would result from using Alectrosaurus rather than Aublysodon as the anchor taxon for Aublysodontrnae.

(Note that the phylogenetic taxonomy proposed by Sereno [1998] is problematic as well: his " Tyrannosauridae " is defined as all taxa closer to Tyrannosaurus thanto Alectrosaurus , Aublysodon , and Nanotyrannus . The latter specimen is very likely a juvenile Tyrannosaunts rex [ Carr 1999; see also below], rendering his " Tyrannosauridae " as a subgroup within the species T. rex [all specimens sharing a more recent common ancestor with the type specimen of T. rex than with the "type " of Nanotyrannus] . Furthermore, Sereno's [1998] " Tyrannosaurinae , " all taxa closer to Tyrannosaurus than to Albertosaurus , Daspletosaurus, or Gorgosaurus , would be limited to the genus Tyrannosaurus itself foilowing the phylogeny presented here. It is recommended that until such time as the more complete Mongolian specimens currently referred to Alectrosaurus olseni [see below], which seem to represent the best materiai of primitive tyrannosaur, are more adequately described, that the provisional phylogenetic taxonomy proposed here be used for tyrannosaurid systematics.)