A team of American scientists showed that the offspring of huge carnivorous dinosaurs like the T-Rex, which grew from the size of a cat to a massive creature, worked on their ecosystem by competing with smaller species.
Their study, published Thursday in the prestigious journal Science, helps answer a lingering mystery about the 150 million years or so dinosaurs that ruled: Why were there so many more small species, so is it the opposite of terrestrial animals today?
“The dinosaur communities were like shopping malls on Saturday afternoons, full of teenagers,” says Kat Schroeder, a researcher at the University of New Mexico who led the study.
She explained that these “adolescents” represent “a large portion of individuals of some kind who seem to have had a real impact on the resources available in their communities.”
Even with a limited number of fossils, experts believe that dinosaurs globally were not very diverse: there are only about 1,500 known species, compared to the tens of thousands of mammal and bird species today.
Over the entire Mesozoic era, between 252 and 66 million years ago, there were relatively more large dinosaur species weighing one ton, compared to those weighing less than 60 kg.
According to some scientists, knowing that even the largest dinosaurs start their life very young due to their presence in eggs before birth, it is possible that they occupy the resources of smaller species, in ecosystems where it was natural to be queens.
To test this theory, Kat Schroeder and colleagues looked at fossil data from around the world, from 550 different species, dinosaurs organized by size and whether they were herbivores or carnivores.
Discover an amazing crater for medium-sized carnivorous dinosaurs in any community where megatheropods, or giant predators such as Tyrannosaurus rex, have been found.
“There are very few carnivorous dinosaurs that weigh between 100 and 1,000 kilograms in large legged societies,” says Kat Schroeder. “And the little giants fill exactly that space.”
This conclusion is supported by how dinosaur diversity evolved over time. The Jurassic period (between 200 and 145 million years ago), had smaller holes in this category, when the Cretaceous period (between 145 and 65 million years ago) had very large holes.
This was because the gigantic teenagers from the Jurassic period looked more like adults, and there was a greater diversity of herbivores to hunt.
“The Cretaceous, on the other hand, is dominated by tyrannosaurs and applesaurs, which evolve a lot when they get older,” the researcher explained.
“I think we are slowly starting to understand dinosaurs as animals, and we are no longer looking at them as cool things, where I left paleontology, and where they were long ago,” she said she was happy with Agence France-Presse.