Tyrannosaurus rex was around longer and grew more slowly than scientists once believed. A recent study changes our understanding of this iconic dinosaur.
In a new analysis published in PeerJ, researchers examined growth rings in T. rex bones. Previously, these rings helped scientists estimate that T. rex stopped growing at about 25 years old and lived to about 30. However, this study revealed that it only reached its full size—around 8 tons—at ages 35 to 40.
Unlike tree rings, which show growth over many years, dinosaur growth rings mainly capture the final decade of life. The team used a new method that revealed previously hidden rings from 17 individual specimens, allowing them to construct a detailed growth timeline.
By analyzing the largest set of T. rex data ever compiled, researchers found that these dinosaurs took their time growing up. As lead author Holly Woodward from Oklahoma State University shared, T. rex spent much of its early life in a mid-size range, rather than quickly reaching its full 40-foot length. This slower growth may have helped it adapt to different food sources throughout its life.
Interestingly, growth rates varied between individuals, suggesting that they were influenced by food availability and environmental factors. This insight enables scientists to grasp the T. rex’s role in ancient ecosystems better.
The discovery also raises questions about whether T. rex is a single species or a complex of related species. A related study recently found that fossils thought to belong to a young T. rex were actually from a different dinosaur known as Nanotyrannus. Some believe this indicates that what we term T. rex might encompass multiple species.
Steve Brusatte, a paleontology professor at the University of Edinburgh, praised the findings. He noted that this research indicates more variety within T. rex than previously thought and suggests that some fossils might represent different dinosaurs altogether.
Moreover, the growth rate findings may lead paleontologists to rethink how they study dinosaur growth. According to Nathan Myhrvold, a co-author and paleobiologist, the protocols used in growth studies may need significant adjustments.
Understanding T. rex’s slow growth can help explain why it thrived as a top carnivore millions of years ago. By occupying various food niches, T. rex’s survival strategy was better diversified than previously believed. This study adds deeper insight into the life of one of history’s most fascinating creatures.
