Baby T. rexes were covered in peach fuzz and the size of small turkeys — here’s what they looked like

We usually think of the T. rex as a monstrous predator, but their babies were almost defenseless.

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We usually think of the T. rex as a monstrous predator, but their babies were almost defenseless.
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R. Peterson / © AMNH

  • Since its discovery more than 110 years ago, the Tyrannosaurus rex has become one of the most popular and widely studied dinosaurs.
  • But paleontologists’ understanding of the T. rex has changed significantly over the past 15 years.
  • A new exhibit at the American Museum of Natural History depicts the predator not as the scaly terror shown in “Jurassic Park” but as a feathered hunter with vulnerable infants.
  • Scientists also now know that baby T. rexes were the size of turkeys, sported fuzzy feathers like ducklings, and had a high mortality rate in their first year of life.

It’s hard to imagine a Tyrannosaurus rex as a baby.

But it turns out that T. rex hatchlings were fairly weak and helpless – most didn’t live past their first birthday and succumbed to disease, other predators, or food shortages. The young dinosaurs also looked something like ducklings and were covered in a downy layer of fuzz.

Baby T. rexes sported a coat of fuzzy feathers.

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Baby T. rexes sported a coat of fuzzy feathers.
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D. Finnin/American Museum of Natural History.

A new exhibit at the American Museum of Natural History, called “T. rex: The Ultimate Predator,” is illuminating these and other recent findings about the “king of the dinosaurs” to correct previous misconceptions about the T. rex.

“Everyone’s preconceived ideas of what T. rex acted like and looked like are going to be heavily modified,” Mark Norell, a curator of the new exhibit at the museum, told Business Insider. Here’s what we’ve learned about tiny T. rexes.

T. rexes had impressive growth spurts

A baby T. rex had more than a 60% chance of succumbing to predators, disease, accidents, or starvation during its first year of life.

Despite this vulnerability, scientists aren’t sure whether or not T. rex parents cared for their young before or after they hatched. No T. rex eggs or nests have ever been found, but fossils of other Tyrannosaur relatives suggest that they laid elongated eggs, roughly 20 or more at a time.

Most T. rex hatchlings never made it past age one.

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Most T. rex hatchlings never made it past age one.
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R. Peterson /©AMNH

Adult T. rexes may have guarded their nests the way birds and crocodile parents do (those are their closest modern relatives), and fed their young, but there is no direct evidence of prenatal care. Fossilized footprints do show, however, that Tyrannosaurs traveled together.

The T. rexes who made it through their first year grew incredibly quickly after that, gaining up to 1,700 pounds per year until they reached full adult size at age 20.

Dinosaur bones, much like trees, have growth rings that correspond to the animal’s age. Experts can count the number of rings to determine how old a T. rex was when it died and can also determine how fast a dinosaur was growing at different ages by comparing the spaces between growth rings.

Based on those bone records, T. rexes appear to have grown five times faster than a human does.

Adult T. rexes relied on their strong bite

Once the fuzzy predators made it past infancy, they grew quickly into fierce predators. Juvenile and adult rexes likely hunted different prey, and probably lived in different habitats. Because they were smaller and lighter than adults, young T. rexes were lithe and fast hunters. They used their forelimbs to snatch prey, but their blade-like teeth could not yet crush bone like adult T. rex teeth could.

Although not yet the tyrant “king,” a 4-year-old T. rex would have weighed about five times more than a 4-year-old boy.

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Although not yet the tyrant “king,” a 4-year-old T. rex would have weighed about five times more than a 4-year-old boy.
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Illustration by Zhao Chuang, courtesy of PNSO

Adult T. rexes could get up to 43 feet long and weighed up to 9 tons. But that weight made it impossible for them to run and leap like their juvenile counterparts. Instead, they walked at impressive speeds of up to 25 mph.

Read more: The T. Rex couldn’t actually sprint like it does in ‘Jurassic Park’ – but it was still a deadly creature

Grown T. rexes didn’t need their meager forelimbs to grab a meal and instead killed prey using their enormous jaws, which were lined with serrated teeth. Those teeth got replaced throughout the animal’s life – new sharp ones were constantly growing in.

Adult rexes could bite with a force of 7,800 pounds – the strongest of any predator alive today – which allowed it to chomp through solid bone.

T. rexes lived short lives

A full-grown T. rex weighed between 6 and 9 tons, and was up to 43 feet long.

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A full-grown T. rex weighed between 6 and 9 tons, and was up to 43 feet long.
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Illustration by Zhao Chuang/courtesy of PNSO

Paleontologists think juveniles had scales and feathers for camouflage and warmth, which may have also played a role in attracting mates. By the time it was fully grown, however, the T. rex probably lost most of its plumage, though it retained a streak of feathers along its arms, tail, and head. The rest of its body was covered in scales.

No T. rex lived past age 30, according to experts at the American Museum of Natural History.

Because their lives were short but action-packed, Gregory Erickson, a paleontologist who consulted on the new exhibit, said the T. rex is “the James Dean of the dinosaurs.”