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. 2010 Mar 2;8(3):e1000321. doi: 10.1371/journal.pbio.1000321

Figure 3. T. rex trotting along beside a T. rex-sized chicken.

Figure 3

Calculations of the muscle mass required to power a fast-running T. rex showed that this was impossible—a 6-tonne chicken would have needed leg muscles making up almost 100% of its body mass. Realistically, T. rex had the muscles to run at about 5 meters per second (18 km/h, 11 mph) [26]. (Painting courtesy of Luis Rey.)