A detailed analysis of 17 fossil specimens of tyrannosaurus rex indicates that this iconic dinosaur grew much more slowly than previously believed, reaching an adult weight of approximately 8 tons by around age 40. This challenges earlier assumptions about its life history.
tyrannosaurus rex holotype specimen at the Carnegie Museum of Natural History in Pittsburgh, USA. Image credit: Scott Robert Anselmo / CC BY-SA 3.0.
tyrannosaurus rex is renowned as one of the most iconic non-avian dinosaurs, continually captivating paleontologists and the public alike.
Previous growth studies proposed that this ancient predator could exceed 8 tons within just 20 years and live for nearly 30 years.
Utilizing advanced statistical algorithms, the new research examined bone slices under specialized lighting, uncovering hidden growth rings that previous studies had overlooked.
This analysis not only extended the growing season for tyrannosaurus rex but also suggested that by age 15, some specimens might not be complete individuals of tyrannosaurus rex, but instead could belong to other species or unique variants.
“This is the largest dataset ever collected regarding tyrannosaurus rex,” stated Holly Woodward, a professor at Oklahoma State University.
“Through studying the tree rings preserved in fossilized bones, we reconstructed the growth history of these magnificent creatures year by year.”
Unlike the annual rings found in tree stumps, the cross-sections of tyrannosaurus rex bones only record the final 10 to 20 years of an individual’s life.
“Our innovative statistical approach allowed us to estimate growth trajectories by synthesizing growth records from various samples. We examined every growth stage in greater detail than any prior studies,” explained Dr. Nathan Myhrvold, a mathematician and paleontologist at Intellectual Ventures.
“The resulting compound growth curves provide a more accurate representation of how tyrannosaurus rex matured and evolved in size.”
Rather than competing for dominance into adulthood, tyrannosaurus rex demonstrated a gradual and steadier growth pattern than previously assumed.
“The prolonged growth phase over 40 years likely enabled young tyrannosaurs to occupy various ecological roles within their environment,” said Dr. Jack Horner of Chapman University.
“This may explain how they maintained their status as apex carnivores at the end of the Cretaceous period.”
The team’s findings were published in the online journal Peer J.
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HN Woodward et al. 2026. Long-term growth and the extension of subadult development of the tyrannosaurus rex species complex revealed through expanded histological sampling and statistical modeling. Peer J 14: e20469; doi: 10.7717/peerj.20469
Source: www.sci.news
