Fig. 5. Step sequence of Gorgosau- rus libratus metatarsus in lateral view, showing forces acting on bones and lig- aments during linear locomotion. Sil- houettes depict the tyrannosaurid at appropriate locomotory stages. Vector sizes represent relative magnitude of forces; yellow, resultants of compres- sive force on bone; red, muscle forc- es; green, tensile forces on liga- ments. Compressive loading on MT III stretches stiff ligament fibers ori- ented along the long axis of the metatarsus. The ligaments transmit this force to MT II, which is pulled dorsomedially. MT II thus transmits its own compressive loadings, and those of MT III, across the mesotar- sal joint. MT IV also transfers load- ings from MT III, but is omitted here for clarity. a: Prior to footfall, liga- ments suspend metatarsus and toes; flexor muscles draw toes forward. b– e: Differential forces on metatar- sal III and outer metatarsals stretch intermetatarsal ligaments, which return elastic strain energy. For clarity, displacement of MT III is exaggerated and articulating bones and bending components are omit- ted. e': MT II (left element) and MT III (right element), from a left meta- tarsus of Tyrannosaurus rex (LACM 7244/23844: cast TMP 82.50.7). Green indicates ligament scars on MT II below and MT III above, slop- ing away from the plane of the fig- ure. The portion of either bone that lies anterior to the other in a given region is rendered transparent.