Press Release: Tyrannosaurus rex grew twice as fast as previously thought; Rapid growth came at a cost of slower locomotion later in life

October 13, 2011 Science

A new study, led in part by The Field Museum, used highly accurate 3-D laser scans of real skeletons to reveal that Tyrannosaurus rex grew more quickly and became much heavier than previously estimated. By comparing T. rex skeletons, including our famous T. rex SUE – the world’s largest and most complete T. rex – an international research team concluded that the “king tyrant reptile” must have grown about twice as fast as previously estimated.

According to the study, SUE weighed over 9 tons when fully grown – 30 percent heavier than scientists previously estimated. The study also showed that T. rex grew as fast as 3,950 pounds per year during the teenage growth period, which is more than twice the previous estimate.

The new study used accurate 3-D laser scans of real T. rex skeletons. Previous estimates of the weight of an adult T. rex were developed by building scale models and used equations relating to body weights of other animals, or computer models that estimated the “fleshy” dimensions of body parts differently.

The study also concluded that the locomotion of T. rex slowed as the animal grew. This is because its torso became longer and heavier while its limbs grew relatively shorter and lighter, shifting its center of balance forward. Thus T. rex wasn’t the fastest of land animals. The study supports the relative consensus among scientists that big tyrannosaurs could run at peak speeds of about around 10-25 miles per hour. The study used CT scan data of SUE provided by the Chicago Police Dept. and Loyola University Medical Center. The study is titled “A computational analysis of limb and body dimensions in Tyrannosaurus rex with implications for locomotion, ontogeny, and growth.” It was just published in the online journal PLoS One.