T. rex fossil discovery rewrites dinosaur history and reveals how long they really lived

A groundbreaking study of Tyrannosaurus rex fossils has rewritten what humans knew about these prehistoric predators and how long they lived millions of years ago.

A study by three US researchers found that T. rex did not reach full adult size until about 40 years of age, maturing slowly and steadily over decades rather than stopping suddenly early in life.

This means that the oldest T. rex likely lived well beyond its 40s and enjoyed a long ‘adolescence’ period during which it continued to grow and strengthen into middle age.

Before this study, experts believed that T. rex stopped growing by age 25, based on previous counts of bone growth rings, suggesting a faster path to maturity.

But by dissecting the fossilized leg bones of these dinosaurs and examining them under special lights, the researchers counted hidden growth rings that recorded annual slowdowns in growth similar to those found in trees by humans.

Using advanced computer models to combine data from multiple T. rex fossils, the team created a more accurate growth curve that took into account variations and extra scars caused by extreme factors such as food shortages or environmental stress.

Mathematician Nathan Myhrvold of Oklahoma State University Health Sciences Center said: ‘Interpreting multiple closely spaced growth signals is a difficult task.’

‘We found strong evidence that protocols typically used in growth studies may need to be revised.’

Scientists were able to calculate how old 17 dinosaurs were by examining rings found in fossilized bones.

The bones came from 17 tyrannosaur specimens collected mostly from museums in Montana and North Dakota, including well-known dinosaurs nicknamed ‘Jane’ and ‘Petey’ that showed unusual growth patterns.

The study was published on: PeerJ magazineHe found that the growth rings inside T. rex bones each show a year of life, with solid lines marking times when growth has stopped completely and fuzzy bands indicating growth slowing.

To do this, scientists polished slices of fossils until they were barely visible and examined them under a special type of microscope that uses polarized light, making hidden details in the fossils stand out even more.

Normally, dinosaur bone growth rings are very difficult or impossible to see clearly with normal microscope light, but special filters created brilliant colors and sharp contrasts that reveal each ring in stunning detail.

By counting each mark on the fossils, including extremely close lines believed to be caused by stress, the team developed four different counting methods and used computer models to test which gave the most consistent picture of dinosaur lifespan.

The most reliable method showed that T. rex grew much more slowly than previous studies had claimed, taking about 35 to 40 years to reach its maximum size rather than maturing in its 20s.

Scientists believe these predators can gain 800 to 1,200 pounds per year, when their fastest growth spurt occurs between the ages of 14 and 29.

However, T. rex’s overall growth process now appears to span decades.

Slices of T. rex leg bones viewed under polarized light to find previously unseen growth rings

Following this rapid growth spurt at puberty, the study concluded that T. rex entered a long “subadult” phase and continued to slowly add weight and size for another 10 to 15 years before eventually evolving into full adult dinosaurs.

Check out co-author Jack Horner of Chapman University in California added to a description: ‘A forty-year growth phase may have enabled young tyrannosaurs to take on a variety of ecological roles in their environment.’

Horner suggested that this slow path to maturity likely allowed young T. rexes to hunt smaller prey, which may have helped them become top predators at the end of the dinosaur age, known as the Cretaceous Period.

However, the team noted that the fossils examined in this study included fossils from the broader ‘Tyrannosaurus rex species complex’, which may have included more than one species or subspecies, skewing the new growth timeline.

Moreover, the smaller fossils of Jane and Petey showed growth patterns that did not match the rest of the fossil group; This suggested that they might actually belong to a different species, such as the proposed ‘Nanotyrannus’.