They are the most infamous — and terrifying — of the dinosaurs but it is only now that we are really getting to know T. rex
From the time it was described in 1905, Tyrannosaurus rex has been the most famous of dinosaurs. It was dubbed the “Prize-Fighter of Antiquity” by The New York Times when its partial skeleton first went on display at the American Museum of Natural History in New York, and just about any superlative applicable to dinosaurs — biggest, meanest, most terrifying — has been applied to it.
Despite its celebrity status, however, the origins of Tyrannosaurus remained mysterious for decades. Its status as a rapacious carnivore was obvious from its massive skull full of banana-sized teeth, but where did it and its close relatives (such as Albertosaurus, Gorgosaurus, Tarbosaurus, and Daspletosaurus) come from?
The man who gave the dinosaur its name, Henry Fairfield Osborn, believed that Tyrannosaurus was the culmination of an unbroken line of predatory dinosaur evolution, with Tyrannosaurus representing the mighty successor to the smaller, but still imposing, Allosaurus of the Jurassic, although an alternative model saw the “tyrant reptile” and its kin as being derived from smaller, raptor-like dinosaurs. Since nearly all the known tyrannosaurs came from the Late Cretaceous, the slice of time just before the extinction of the non-avian dinosaurs 65 million years ago, it was difficult to tell which hypothesis was correct, since all the known tyrannosaurs were specialised predators from near the end of the dinosaurs’ reign.
During the late 20th century, however, palaeontologists who studied tyrannosaurs were able to pick out traits that allied them with a diverse group of much smaller predatory dinosaurs — the coelurosaurs. As it turned out, the “tyrannoraptor” hypothesis seemed to be correct, but the fossils that illustrated the evolution of the tyrants still remained frustratingly elusive.
Some of those forms have now been found. University of Maryland palaeontologist and tyrannosaur expert Thomas Holtz says: “The past decade has seen an explosion of discoveries of new, early tyrannosauroids that helps us to fill in many of the previously missing phases of tyrant evolution.”
As was predicted by the evolutionary relationships that palaeontologists had previously teased out through their analysis of some of the last tyrannosaurs to evolve, the earliest forms were small, raptor-like dinosaurs that were distributed across the northern hemisphere. Among the earliest members of the tyrannosaur family, the 165-million-year-old Proceratosaurus from England and the 155 million-year-old Guanlong from China, did not look very much like their later cousins, especially since their long, shallow skulls were decorated with crests.