Dinosaur 'teenage terrors' crowded out the competition
As adults, huge meat-eating dinosaurs such as Tyrannosaurus rex - sometimes topping 9 tons in weight - ruled the Cretaceous Period landscape. But even as juveniles, scientists said on Thursday, these fearsome species - together called megatheropods - dramatically reshaped the composition of dinosaur communities around the world, crowding out midsized carnivorous competitors.
Researchers examined dinosaur communities - the species of meat-eaters and plant-eaters inhabiting the same place at the same time - in 43 locations globally during the Jurassic and Cretaceous Periods, spanning the final 136 million years of the dinosaur age. Carnivorous dinosaurs came from a group called theropods. The largest were the megatheropods, bipedal brutes with large skulls, strong jaws and menacing teeth.
Cretaceous dinosaur communities that included a megatheropod - defined as a predator weighing at least a ton - were also populated with small predators - under about 220 pounds (100 kg) - but typically lacked midsized meat-eaters between those two weight ranges.
This "gap" appears to have been caused by the presence of juvenile megatheropods that grew from babies the size of a small dog into teenage terrors before achieving adult dimensions.
These juveniles filled an ecological niche - using a unique set of physical attributes to target intermediate-sized prey - that otherwise might have been occupied by another species. "Just like when parents drop their teens off at the mall to get them out of their hair, Mesozoic communities might have been separated by ages, with adult megatheropods hunting and consuming in their own way, while juveniles of the same species were doing something completely different," said University of New Mexico paleoecologist Kat Schroeder, who led the study published in the journal Science.
The Mesozoic Era was the geological time span often called the age of dinosaurs. Juveniles of North American Cretaceous megatheropods like Tyrannosaurus and Albertosaurus were relatively light and agile, Schroeder noted, making them well-suited to hunt different prey, compared with bigger and bulkier adults with bone-crushing jaws and proportionally shorter legs.
These dinosaurs lived to roughly age 40, with big growth spurts as teens. The scarcity of midsized predators was not as pronounced during the preceding Jurassic Period. The researchers noted that the body plan of Jurassic megatheropods like Allosaurus and Torvosaurus generally did not change as much over time as those during the Cretaceous.
This story has been published from a wire agency feed without modifications to the text.