The study is based on the analysis of the fossils of smaller T. rexes.
Tyrannosaurus rex, the iconic apex predator of the Late Cretaceous period, ruled Earth around 68 to 66 million years ago. Known for its massive size, powerful jaws, and tiny forelimbs, T. rex (as it's popularly known) was a formidable carnivore, likely preying on large herbivorous dinosaurs. With its distinct serrated teeth and robust build, this fearsome predator has captivated scientific and popular imagination. But now, a new study has shed fresh light on the miniature version of the famed T. rex.
The species, Nanotyrannus lancensis, was first named decades ago but later reinterpreted as a young T. rex.
The study is based on the analysis of the fossils of these smaller T. rexes. Till now, these dinosaurs were considered the young versions of the famed giants. But researchers from University of Bath and University of Chicago have claimed it was a separate species.
The study has been published in the journal of Fossil Studies.
"If they were young T. rex they should be growing like crazy, putting on hundreds of kilograms a year, but we're not seeing that," Dr Nick Longrich, co-author of the study, said.
"We tried modelling the data in a lot of different ways and we kept getting low growth rates," the researcher added.
The study found that bone growth rates were slowing and indicated that the Nanotyrannus versions of the famous dinosaurs were likely almost full size.
But there were at least 150 distinct features in these smaller dinosaurs that set them apart from T. rexes, said the study.
"The arms are actually longer than those of T. rex. Even the biggest T. rex has shorter arms and smaller claws than in these little Nanotyrannus. This was an animal where the arms were actually pretty formidable weapons. It's really just a completely different animal - small, fast, agile. T. rex relied on size and strength, but this animal relied on speed," said Dr Longrich.
The study has sparked a debate in the scientific world.
"I have no problem with Nanotyrannusbeing a real thing if science shows that. I'm not convinced that their interpretation is more accurate than ours," said Holly Woodward, the author of a previous study on these dinosaurs. The 2020 study by researchers at Oklahoma State University had called them smaller T. rexes.