The discovery of Sue, one of the most complete and well-preserved Tyrannosaurus rex skeletons, offered an unparalleled window into the life of this prehistoric predator. Unearthed in 1990, Sue quickly became a scientific marvel, providing paleontologists with a wealth of information about T. rex biology and behavior. While her nearly 90% complete skeleton has revealed much about her existence, the precise circumstances surrounding her death approximately 67 million years ago remain a subject of ongoing scientific inquiry and debate.
The Skeletal Clues
Sue’s fossilized remains bear a remarkable record of her life, including numerous injuries and conditions. She had several broken and healed ribs, with one even mending into two pieces.
Her left fibula was larger than her right, indicating a severe injury and bone infection, likely causing chronic pain and swelling. Arthritis in her fused tail vertebrae suggests stiffness as she aged, and a significant injury to her right shoulder blade and a torn ligament in her right arm also point to past struggles.
Perhaps one of the most discussed features is the series of round holes on her lower jawbone. While initially theorized as a parasitic infection, newer research suggests these holes show signs of healing, indicating she survived whatever caused them.
Unraveling the Cause of Death
The array of injuries and ailments found on Sue’s skeleton has led scientists to propose several theories about her demise. One hypothesis centered on a parasitic infection, once thought to be responsible for jaw holes, which could have caused severe throat swelling and led to starvation. However, recent studies suggest these jaw lesions were healed injuries and not directly fatal.
Another possibility is that the accumulation of chronic pain and severe injuries, such as the infected fibula and arthritis, significantly hampered her ability to hunt. An animal of Sue’s immense size, estimated at 9 tons, required vast amounts of food, and impaired hunting could have led to starvation.
While some injuries were healed, the overall burden of these pathologies could have weakened her, making her susceptible to other factors or old age. The exact cause remains unknown, but scientists consider scenarios like severe infection, starvation, or complications from her many ailments.
Antemortem Versus Postmortem Injuries
Paleontologists distinguish between injuries sustained during an animal’s life (antemortem) and damage that occurred after death (postmortem) to accurately interpret fossil evidence. Antemortem injuries are identifiable by signs of healing, such as new bone growth, rounded edges around a fracture, or rejoining of broken pieces. This indicates the animal survived the injury long enough for tissues to repair the damage.
In contrast, postmortem damage shows no evidence of healing. This damage can result from scavenging, geological pressures during fossilization, or excavation. Postmortem breaks often have sharp, jagged edges and appear brighter than surrounding bone. Differentiating between these types of damage is essential for understanding an animal’s life history and forming hypotheses about its cause of death.