PROFESSOR THOMAS CARR - Tyrannosaurus rex and its immediate
relatives, the tyrannosauroids, are instantly recognisable with
their gigantic bodies, large heads, huge teeth, short arms, and
massive legs and tails. For a long time the question of how
those features developed during an individual’s growth was
unknown because juvenile specimens were not closely studied or
they were misidentified as pygmy adults of unique species. In
fact, the differences between juvenile tyrannosauroids and their
adult counterparts are so extreme that the growth changes in
these dinosaurs are as remarkable as the evolutionary
transformation that turned nonflying theropods into flying birds
over millions of years. It turns out that all of the best-known
large tyrannosauroids (Bistahieversor, Albertosaurus,
Gorgosaurus*, Daspletosaurus, Tarbosaurus*, and Tyrannosaurus)
share the same basic growth pattern – a pattern so similar that
it is difficult to tell the juveniles of the different genera
and species apart! It is only later in g