The Tyrannosaurs, or to be more precise those Theropod dinosaurs that make up the family Tyrannosauroidea are perhaps the best known of all the different types of dinosaur. One of the last, and one of the largest Tyrannosaurs to evolve was the fearsome Tyrannosaurus Rex (Tyrant Lizard King). This dinosaur held the record for being the biggest and most powerful land-living predator of all time for the best part of a Century, no respectable dinosaur movie was complete without a T. Rex or two popping up to chase and consume a few people. T. Rex lived at the very end of the Cretaceous, in a part of the world we now know as the western United States and Canada, although at the time much of America was covered by a warm, shallow sea that scientists call the Western Interior Seaway.
Tyrannosaurus Rex was large with a very deep and powerful skull. Its strong jaws and banana sized teeth gave it perhaps the most powerful bite of any terrestrial predator. Scientists have estimated that it could generate a bite force on the tips of its massive teeth in excess of 15,000 lbs per square inch. This is getting on for fifteen times more powerful than the bite of a modern African Lion (Panthero leo).
However, in the late 1990s evidence of even larger meat-eating dinosaurs began to be discovered. Scientists had speculated that the Spinosaurs, in particular the remains of one such creature whose fossilised bones were found in 1911, just a few years after T. Rex had been formally named and described, were at least as large a Tyrannosaurus Rex. Fossils found in South America did prove that the Tyrannosaurs did not have it all their own way when it came to being big and really fierce. In 1993, a local fossil collector Ruben Carolini found the fossilised remains of a huge meat-eating dinosaur. The subsequent scientific expedition uncovered the skull of a carnivorous dinosaur that was bigger than any T. Rex skull then known. The scientists then found the jawbone nearby of another such creature that was even bigger. From these discoveries, the “Giant Southern Lizard” came to be described and Giganotosaurus carolini became officially the largest meat-eating dinosaur known from the fossil record and by default, the largest land-living carnivore of all time.
However, the debate as to which was the biggest meat-eating dinosaur still rages, fuelled by more fossil discoveries from the United States, Argentina and North Africa. A new and intriguing field of research has perhaps revealed a trait amongst Tyrannosaurs that had been up until recently not been considered – that these animals may have been pack hunters.
The behaviour of carnivorous dinosaurs was very probably as diverse as that of modern mammalian carnivores. Today, we see social hunters such as lions and wolves as well as apex predators that tend to be more solitary such as leopards and pumas. In addition, some modern predators, regarded as largely solitary do have a form of pack existence for some part of their lives. A female polar bear (currently regarded as the largest land carnivore living today), will have her cubs with her for a considerable period, although it is the adult that does the hunting. Tigers too, very much regarded as solitary hunters do form packs for some part of their lives. Here young cubs spend perhaps as long as two years with their mother and as sub-adults, siblings will often live as a loose collective for a time, prior to reaching sexual maturity. The collective noun for a group of tigers is an “ambush of tigers” – an apt description considering the ambush tactics that most species of tigers employ when hunting prey.
It was Professor Phi Currie and his colleagues who raised the profile of pack hunting in Tyrannosaurs with a paper published in 2000, detailing a study of an Albertosaur (type of Tyrannosaur) bone bed in Canada. The scientific paper was entitled “Possible Evidence of Gregarious Behaviour in Tyrannosaurids”. The remains of at least three Albertosaurs were discovered together in a bone-bed, these dinosaurs were different sizes perhaps they were a part of a pack of these dinosaurs that perished together crossing a swollen river, or perhaps the bodies of these animals were deposited in the same place many years apart after different flood events.
Professor Currie of the University of Alberta and his team speculated that for at least part of the time, large Theropods may have formed packs or family groups. Juveniles may have associated with mature animals in packs and therefore not competed for food with smaller kinds of Theropods. After a five-year research programme further evidence as to pack behaviour of large species of Tyrannosaurs has been uncovered in the Gobi desert. Phil Currie has been at the forefront of this research, working closely with counterparts from Chinese museums, including the Institute of Vertebrate Palaeontology and Palaeoanthropology. This time, the Tyrannosaur concerned is Tarbosaurus bataar a close relative of Tyrannosaurus Rex. This Asian Tyrannosaurid is the largest Asian predator known with fossils found in China and Mongolia. It was very similar to T. Rex with a slightly narrower snout and smaller teeth. It reached lengths in excess of 12 metres and would have weighed around five metric tonnes.
If Tyrannosaurs, including the likes of Tyrannosaurus Rex were pack hunters then these creatures probably specialised in attacking large herbivores such as Ceratopsians (horned dinosaurs) and Hadrosaurs (duck-billed dinosaurs). Whether these animals remained in family groups for a much of their lives is not known. It is also impossible to determine whether these creatures had any tactics for hunting game. Lions have strategies for hunting on the African plains, wolves too adopt a number of tactics to trap game. Whether Tyrannosaurs were capable of communicating and co-ordinating attacks with perhaps individuals having their own specialised roles to play in the hunt, is unknown.
Tyrannosaurs as pack animals would have been truly formidable. This brings up the intriguing question as to what the collective noun for a pack of Tyrannosaurs should be. A collective noun is a word used to describe a collection of creatures such as a pod of whales, a school of fish or a pride of lions. What would be an appropriate collective known for a group of Theropod dinosaurs? Perhaps we could put forward the proposal for a group of Albertosaurs to be called an “assault” of Albertosaurs.
But what about Tyrannosaurus Rex? What would be the collective noun for a group of these fearsome reptiles, could we suggest a “tyranny” of Tyrannosaurus or how about a “tirade” of T. Rexes?