Tyrannosaurus rex is an iconic predator, among the largest land-dwelling meat-eaters of all time, with foot-long teeth and some of the most powerful jaws ever measured. As an adult, that is. Much like us humans, a tyrannosaur’s teenage years were a bit awkward, with lanky legs and long narrow faces. But young T. rex didn’t just look different; they may have been living entirely different lifestyles than their parents.
Ontogeny refers to the changes an animal experiences as it grows into adulthood. To explore tyrannosaur ontogeny, Rich Bykowski, of Georgia Southern University, examined several different species, including T. rex and a number of its close relatives, focusing on the development of three body parts: the hind legs, the upper jaws, and the teeth.
Young tyrannosaurs were built for speed, at least compared to the adults. The
proportions of their leg bones were comparable to those of fast-running animals today, while the adults had stockier limbs better suited to support a heftier body (think horse versus elephant). This probably reflects a difference in hunting strategy. “[Younger tyrannosaurs] might have been more apt to run down prey as opposed to ambushing and over-powering it as adults,” says Bykowski, who presented his research last month at the annual meeting of the Society of Vertebrate Paleontology. Whether these predators were doing their hunting alone or in groups is still unknown.