Teen tyrannosaurs may have stepped in to fill a void previously held by other meat-eating dinosaur species...
When the mighty Tyrannosaurus rex dominated the land, medium-sized predators all but disappeared - according to a new study.
Instead, teenage tyrannosaurs likely filled this niche - living much of their lives as smaller and faster animals than their parents.
Thomas Holtz from the University of Maryland discovered the predator void when he dug deep into the fossil record from central Asia and western North America.
By surveying records of sixty dinosaur communities from the Jurassic and Cretaceous periods (201-66 million years ago) Holtz compared those that had tyrannosaurs with those that did not have tyrannosaurs.
He then sorted all the meat-eating dinosaurs in these communities into size categories to see if any size classes were missing.
In the study - published in the Canadian Journal of Earth Sciences - Holtz found that “there actually were more missing sizes in the mid-sized predators in tyrannosaur-dominated communities”, in contrast to other dinosaur communities from the same time.
“It turns out that teenage tyrannosaurs filled the void and were the mid-sized predators”, explained Holtz.
As they only spent about one-third of their lives as adults, tyrannosaurs would have spent most of their life in this phase.
These teenage tyrannosaurs were different from the adults, being faster and more agile.
They also weren’t in competition with their parents and other adults, as they preyed on faster, smaller species.
What's still unknown is how teen tyrannosaurs influenced the rest of the ecosystems they lived in. In future, Holtz plans to drill deeper into the fossil record to discover if there were any changes in the size of prey species during this period.
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