Sue, the Tyrannosaurus rex fossil designated FMNH PR 2081, is one of the most famous and well-preserved predatory dinosaur specimens ever unearthed. Discovered in 1990 in South Dakota, this remarkable skeleton provides unprecedented insight into the immense scale of the species. The fossil is now a permanent feature at the Field Museum of Natural History in Chicago, where it serves as a benchmark for understanding the maximum size a T. rex could attain.
The Definitive Measurements: Length and Height
The size of Sue is described using fixed, linear measurements derived directly from the assembled bones. From the tip of its snout to the end of its tail, the specimen measures approximately 40.5 to 42 feet long. This length reflects the dinosaur’s powerful, elongated body structure, which allowed it to balance its great weight on two legs.
Measuring the height of a bipedal dinosaur is typically done at the hips, representing the most stable point of its posture. At the hip joint, Sue stands about 12 to 13 feet tall, comparable to a single-story building. This height allowed the predator to cover significant ground with each stride.
A specific component of Sue’s anatomy is its skull, which measures nearly 5 feet in length. The original skull weighs around 600 pounds, making it so substantial that a lighter replica must be mounted on the skeleton for display. The actual fossilized skull is exhibited separately to prevent potential damage to the articulated neck vertebrae.
Estimating the Weight of a Giant
Determining the mass of an extinct animal like Sue presents a unique challenge, requiring scientists to rely on indirect methods. Early estimates for T. rex utilized the circumference of the leg bones, suggesting a weight closer to 5 to 7 tons. However, this method did not fully account for the animal’s overall girth or the volume of its soft tissues.
Modern paleontologists employ advanced techniques, such as 3D laser scanning, to create fleshed-out digital models of the skeleton. This volumetric modeling approach allows researchers to wrap a digital “skin” around the bone structure, estimating the space occupied by muscles, organs, and other soft tissues. By subtracting the volume of known empty spaces, such as the lungs and oral cavity, a more accurate body mass can be calculated.
Revised studies indicate that Sue was far heavier than previously believed. Current estimates place its living weight in the range of 9 to 10 short tons, or about 8.4 to 9.1 metric tons. Some models have suggested a weight of up to 14 metric tons, underscoring the uncertainty inherent in estimating the mass of an animal with no living counterpart. The consensus is that Sue was a robustly built individual, making it one of the heaviest T. rex specimens currently known.
Why Sue Remains the Largest Specimen
Sue’s reputation as one of the largest T. rex specimens is rooted in its exceptional preservation and completeness. Approximately 90% of the individual’s bones were recovered, which is a near-unprecedented level of completeness for a large predatory dinosaur. This high percentage allows scientists to reconstruct the skeleton with high confidence, minimizing the guesswork required for missing elements.
The completeness of the fossil provides the necessary framework for accurate size analysis and a reliable baseline for linear and volumetric measurements. Without this high degree of preservation, any size estimate would be subject to greater potential error and scientific debate.
Analysis of the bone structure, using growth rings similar to those found in trees, indicated that Sue was about 28 years old at the time of death. This age places the individual at the upper end of the estimated lifespan for T. rex, suggesting it lived long enough to achieve its maximum potential size. The combination of advanced age and completeness confirms Sue as a fully mature individual that had reached the physical peak of its species.