Like big carnivorous dinosaurs Tyrannosaurus Rex Were the top bandits of his time. And apparently not only when fully developed, but also as a teenager. Even as young animals, they were so effective that they largely ejected other predatory dinosaur species. This is what biologists write around Caitlin Schroeder of the University of New Mexico In “Science” magazine.
According to their fossils, dinosaur communities constitute a strange category of species. Typically, in vertebrates, smaller species are more numerous than larger species. With the “terrible lizards” of the Middle Ages it seems to be the other way around. Biologists are surprised why this can happen. This may play a role in that fossils of the time are only incompletely preserved. But obviously there is more to it than.
Colossi only and elves
Schroeder and his team have investigated 43 dinosaur communities that have been handed over in fossil form. The dates are 136 million years old and include seven continents and 550 species. As the researchers noted, there was a strange void in communities at the time: there was a shortage of carnivorous dinosaurs weighing between 100 and 1,000 kilograms. However, small and large species were represented. “It’s as if there were no hunters in the African Krueger National Park between the spoonbill and the lion,” biologists write.
Where did the difference come from? Did other carnivores replace medium-sized predator dinosaurs? Probably not: Mammals of the time were very small with a maximum of 15 kg, and crocodiles could not move very far from the water.
According to Schroeder and his colleagues, offspring of large carnivores outnumbered the medium-sized competition. Because large predators were as large as dinosaurs – their young eggs were hatched, and they could not be of any size. A new hat T rex Was about the size of a small domestic dog. Within 16 to 19 years it developed into a colossus of twelve meters long and ten tons, which on average exceeded 500 kilograms every year. As a result, juvenile persecutors covered a huge size range – and this was true for other top predators such as abelisauride.
As they grew older, animals should gradually occupy very different ecological traces. Because a dog-shaped carnivore hunts completely differently than a giant weight ton. This shift in niche with increasing age (“ontogenetic niche shift”) probably led to large carnivores claiming space as otherwise occupied by medium-sized species. The latter lagged behind. This thesis is also supported by the fact that the young animals of large predator dinosaurs were far more numerous than fully developed specimens, as researchers calculated based on growth and survival curves.
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