Albertosaurus older "Gorgosaurus libratus" (sometimes called "Albertosaurus libratus"; see below). These two species are the only described albertosaurines; other undescribed species may exist. Thomas Holtz found "Appalachiosaurus" to be an albertosaurine in 2004, but his more recent unpublished work locates it just outside Tyrannosauridae, in agreement with other authors. The other major subfamily of tyrannosaurids is the Tyrannosaurinae, which includes "Daspletosaurus", "Tarbosaurus" and "Tyrannosaurus". Compared with these robust tyrannosaurines, albertosaurines had slender builds, with proportionately smaller skulls and longer bones of the lower leg (tibia) and feet (metatarsals and phalanges). Below is the cladogram of the Tyrannosauridae based on the phylogenetic
Caiuajara bones have been three-dimensionally preserved, not compressed, but are only rarely articulated. The individuals found are often juveniles; adult animals are much rarer, only represented by two skulls and three humeri. Good specimens have been assigned as paratypes, the more fragmentary ones have been referred. The paratypes are: CP.V 865: a snout, rear of the mandibula, right jugal, vertebrae, ribs and metatarsals; CP.V 867: a snout and limb bones; CP.V 868: a snout, wing elements and other postcrania; CP.V 869: a vertebral column, right arm, coracoid, breastbone, wing phalanges, belly ribs, pelvic elements and a right thighbone; CP.V 870: a