Using digital models and computer analyses, a paleontologist at the University of Bristol, UK, has studied the muscle strain during jaw opening of three theropod dinosaurs – Tyrannosaurus rex, Allosaurus fragilis and Erlikosaurus andrewsi.
Tyrannosaurus rex, a large theropod dinosaur; theropods were a diverse group of two-legged dinosaurs that included the largest carnivores ever to walk our planet. Image credit: Az Dude.
Dr Lautenschlager looked at Tyrannosaurus rex – a large-sized meat-eating theropod with a massively built skull and long teeth; Allosaurus fragilis – a more lightly built but carnivorous theropod; and Erlikosaurus andrewsi – a closely related but herbivorous member of the theropod family.
“Theropod dinosaurs, such a Tyrannosaurus rex or Allosaurus fragilis, are often depicted with widely-opened jaws, presumably to emphasize their carnivorous nature,” said Dr Stephan Lautenschlager of the University of Bristol’s School of Earth Sciences.
“Yet, up to now, no studies have actually focused on the relation between jaw musculature, feeding style and the maximal possible jaw gape.”
In his study, Dr Lautenschlager found that the feeding style and dietary preferences of theropod dinosaurs was closely linked to how wide they could open their jaws.
“All muscles, including those used for closing and opening the jaw, can only stretch a certain amount before they tear,” the scientist said.
“This considerably limits how wide an animal can open its jaws and therefore how and on what it can feed.”
In order to fully understand the relation between muscle strain and jaw gape, Dr Lautenschlager simulated jaw opening and closing, while measuring the length changes in the digital muscles.
Optimal and maximal jaw gapes for Allosaurus fragilis, Tyrannosaurus rex and Erlikosaurus andrewsi. Image credit: Stephan Lautenschlager.
Tyrannosaurus rex, Allosaurus fragilis and Erlikosaurus andrewsi were also compared to their living relatives, crocodiles and birds, for which muscle strain and maximal jaw gape are known.
The study found that the two carnivorous theropod species were capable of a wide gape (up to 90 degrees), while the plant-eater was limited to small gape (around 45 degrees).
Between the two meat-eaters, results show that Tyrannosaurus rex could produce a sustained muscle force for a wide range of jaw angles, which would be necessary for biting through meat and skin and crushing bone.
“We know from living animals that carnivores are usually capable of larger jaw gapes than herbivores, and it is interesting to see that this also appears to be the case in theropod dinosaurs,” Dr Lautenschlager said.
The results of this study were published online today in the journal Royal Society Open Science.
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Stephan Lautenschlager et al. Estimating cranial musculoskeletal constraints in theropod dinosaurs. Royal Society Open Science, published online November 04, 2015; doi: 10.1098/rsos.150495
