>>9399207https://www.nytimes.com/2021/02/25/science/tyrannosaurus-teenagers-dinosaurs.htmlScientists had been perplexed at how successful a T-rex is. Usually there is way less predator than herbivore in an ecosystem, but T-rex fossil constitutes something like 15% of fossils found in Hell's Creek formation, and as far as we know there is no other competition from similarly sized carnivore in the ecosystem. There is also seemingly a massive transformation toward late stages.
People have hypothesized that T-rex fill different niches during their lives. Juveniles are like cheetahs they are sprint and chase predator. Juvenile T-rex are lanky and have significant leg length ratio that suggest it is a sprinter. As they grew older, they become more of a bruiser, the skull size grew, probably to fight and fend off other T-rexes from stealing its prey. This is more of a niche of a lion in modern africa. This is why there is no medium sized carnivore in the ecosystem, it is just juvenile rex, subadult rex, and adult rex filling different niches as cheetahs, leopards, and lions all at once.
