>>11190888It varies from species to species. Raptorrex has been pretty definitively shown not to be a juvenile Tarbosaurus, because we have actual juvenile Tarbosaurs and they don't look like Raptorrex. It's a juvenile, but if it is a Juvenile of it's own distinct genus or of another animal like Asiatyrannus is not yet known. Of course if Raptorrex is a juvenile Asiatyrannus, then that would mean that Asiatyrannus would be synonymized with Raptorrex since it's the older name.
Longrich thinks that Nanotyrannus is also probably more than one genus, possibly not even all that closely related to each other. He's talked about how the Dueling Dinosaurs Theropod, which is still publicly called a juvenile Tyrannosaurus, but many paleontologists think is Nanotyrannus, is actually an adult/subadult of Stygivenator, which while in the same size range as Nano, Asiatyrannus, and Raptorex, was its own genus.
Dr. Holtz has suggested that Nano may be a juvenile Tyrannosaurus imperator rather than Tyrannosaurus rex. However, given that the Nano fossils are from subadults rather than juveniles, as often described, it's unlikely that they could put on the mass required to grow into T. imperator.
There was supposed to be a big paper on the Dueling Dinosaur's theropod this year, but we've only got a couple of months left and it's not out yet so it might not be out until next year which sucks, but given how long it took before paleontologists could look at it since the ownership rights were caught in legal limbo for so long.
