Discovery of Mass Tyrannosaurus rex Fossil Sites Indicates Social Interaction Rather Than Isolation

Sooraj Shah ’24

Figure 1: Discovery of Tyrannosaurus rex grave sites hint at their social capabilities.

The image of the lone Tyrannosaurus rex fossils sitting in a museum is based on the stereotype that they hunted in solidarity. It has long been debated whether these creatures even had the brain capacity to form communities until recently. A study conducted by Alan Titus, a paleontologist for the U.S. Bureau of Land Management, focused on a new mass grave whose fossils are rewriting what was previously thought of the isolative behaviors of these ferocious predators. 

In 2014, Titus discovered a rare fossil site within the Grand Staircase-Escalante National Monument in Utah while on an expedition to uncover turtle remains. The appearance of a Tyrannosaurid astragalus, or ankle bone, prompted Titus to uncover more of the area until a younger and an older adult were completely exposed, revealing a mass grave of at least four Tyrannosaurid fossils. The team conducted isotope tests on the bones, examining their elemental compositions of carbon and oxygen in order to ensure that this was their original resting place. The fossils were also tested for rare Earth elements which would reveal similarities between the bones. These elements are controlled by pH, rock type, and colloids (non-crystal particles), and revealed great similarity and verified that these fossils were not brought to this area via water displacement. 

The study concluded that Tyrannasaurids may have been much more social than previously thought. The creatures most likely hunted in packs, and the finding that these particular Tyrannosaurids all died in the same location suggests that they operated much like other animal groups such as birds. The discovery of this mass grave and others around the world will open a gateway into understanding the social behavior of Tyrannasaurids. Further research may revolve around understanding the psychological and neurological behavior of Tyrannasaurids based on fossil analysis. 

Works Cited

  1. A. Titus, et al., Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness. PeerJ 9, (2021). DOI: 10.7717/peerj.11013
  2. Image Retrieved from:

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