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The Science of Sue
How To Build A Giant
Tyrannosaurus rex looms large in the public perception of dinosaurs because of its huge size. But how did T. rex attain this phenomenal body size? It’s an evolutionary question that has been pondered by everyone from school children to professional paleontologists.
T. rex is the last of the giant tyrannosaurs, a lineage that evolved from smaller feathered theropods and dominated the northern continents in the Late Cretaceous. Even though many Late Cretaceous tyrannosaurs are large in their own right, weighing between one and three tons as adults, they are dwarfed by their geologically younger, six-ton cousin. Fortunately, we now have a good sample of various tyrannosaurs from North America, allowing a team of paleobiologists–led by Dr. Gregory Erickson of Florida State University and including Dr. Mark Norell and Dr. Phil Currie in addition to myself–to examine just how T. rex outgrew its closest relatives. In the process, we gained valuable insights into the life history of tyrannosaurids.
To determine how animals grow, one needs to know the weight and corresponding ages of a series of individuals covering all developmental stages. From these two parameters, one can construct a growth curve that reveals how fast a species grows at a given stage of its life. But how does one determine the age and mass of an extinct creature from its fossilized bones alone? The age problem can be solved by studying growth-related features of the skeleton.
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