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 Thomas Holtz found "Appalachiosaurus" to be an albertosaurine in 2004, but his more recent unpublished work locates it just outside Tyrannosauridae, in agreement with other authors.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
Roll the Bones strong vocal melodies at the beginning and base the rest of the tune around it. Lifeson had wanted to try playing funk rhythms and attempted it "Presto" and wished to explore it further on "Roll the Bones". The majority of the arrangements worked out at the writing stage remained unchanged which allowed the group to use the demos as a guide for recording, done by transferring the completed demos to 24-track and re-recording the parts. The album contains a running lyrical theme concerning the element of chance in different aspects of life, which Peart had devised while experimenting with lyrics.