Preserved vessel canals reveal how much blood nourished the bone, a proxy for the bone’s growth rate. Woodward examined these translucent slivers up close to look for hidden detail. They then took even thinner slices and ground them down to the thickness of a human hair-thin enough for light to pass through the fossilized bone.
The team first removed thin slices from the two individuals’ leg bones and embedded the slices in plastic resin. The other, which is unnamed, is less complete but was probably bigger than Jane. One, named Jane, is a nearly complete tyrannosaur fossil that’s about 21 feet long. For this study, Woodward and her team focused on two dinosaur specimens found in Montana and housed at Illinois’s Burpee Museum of Natural History.
“We know that had to grow fast to go from a hatching probably no bigger than a pigeon into an adult larger than a bus, but we don't know a lot about how it grew during its teenage years,” Steve Brusatte, a paleontologist at the University of Edinburgh who reviewed the study, says in an email.Įnter Woodward, whose childhood fascination with microscopy led her to study the tiny structures preserved in dinosaur bones. As bones grow, they constantly remake themselves, which gradually erases the bone laid down in childhood. In two influential 2004 papers, researchers suggested that it went through a growth spurt in its teenage years, putting on an average of five pounds a day. rex showed that the dinosaur grew to a massive size by the time it reached its mid-20s. “We still know very little about its life history: how it grew up from hatching out of an egg to a 9,000-kilogram beast.” 'Fossil unicorn' “There’s still a lot to learn about dinosaurs, even a dinosaur as famous as Tyrannosaurus rex,” says lead study author Holly Woodward, a paleontologist at the Oklahoma State University Center for Health Sciences. In the latter case, the fossils offer a rare glimpse at an important developmental stage in the life of this dinosaur icon. So, either an adult Nanotyrannus hasn’t been found yet-or Nanotyrannus really is a teenage T. The new study offers the first hard data on the small-scale structure of some purported Nanotyrannus bones, confirming that two candidate fossils are in fact juveniles. Find out about the two major categories of fossils, how fossilization occurs, and how fossils can help paint a picture of the planet's history. rex.įossils are echoes of an ancient past. However, subsequent studies have led most experts to agree that the fossils assigned to Nanotyrannus are probably juvenile T. In the 1980s, paleontologists examining a set of small, slender carnivores concluded that the Cretaceous fossils belonged to their own distinct tyrannosaur species. The research also casts further doubt on the existence of Nanotyrannus, a controversial “pygmy” tyrannosaur proposed to have lived alongside T. ( Also find out about “Scotty,” the biggest T. rex’s growth rates varied as it aged, and that these predatory dinosaurs could seemingly slow their growth when food was scarce, potentially giving them an evolutionary leg up. In a study published in Science Advances on Wednesday, researchers reveal a stunningly detailed analysis on cross-sections of bone from juvenile tyrannosaurs. rex remains pulled from the region’s Cretaceous-period rocks, scientists have had few clues about how the celebrity dinosaur grew from a hatchling to a gargantuan predator-until now. Sixty-six million years ago, the ground of western North America trembled with the footfalls of a tyrant: Tyrannosaurus rex.
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