Avisauridae leg formed by fused metatarsals (the bones which comprise the foot in humans). As a result, members of this family are distinguished from other enantiornitheans exclusively by features of the tarsometatarsal and pedal phalanges (toe bones). Unlike in some prehistoric birds, avisaurid tarsometatarsals were not completely fused, with the distal (outer) parts of the metatarsals being separate from each other. The proximal (near) half of metatarsal III (the long bone in the middle of the tarsometatarsus) is convex from the front. The inside edge of this bone's trochlea (toe joint) has a bony tab which points downward, known as a
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.