Back in 1988, paleontologist Robert Bakker and his fellow colleagues from the Cleveland Museum of Natural History in Ohio re-labeled an exemplar first unearthed in 1942 and shown at the museum. The team claimed it was the first-known specimen of a small new group they named ‘Nanotyrannus.’
Later on, in 2001, another team of researchers found an almost complete skeleton of a small Tyrannosaurus in the proximity of the town of Ekalaka in Montana, in a place known for its fossil formation called Hell Creek. They named the specimen Jane and labeled it as a young Tyrannosaurus Rex.
However, a few experts kept insisting that the creature was a part of the newly classified Nanotyrannus group, indicating to the anatomical structure of its skull and bones, which, allegedly, was not similar to those of adult T. rex.
Examining Bones to Find Clues
In a research published in the journal Science Advances, scientists led by Holly Woodward of Oklahoma State University examined samples from the inner part of Jane’s tibia and femur bones, as wells as a set of bones from a creature known as Petey, under a microscope.
This method, known as paleohistorology, determined that the two specimens were young individuals and not adults. Therefore, the paper’s authors say, the existence of the Nanotyrannus species is very improbable.
“The really cool thing about fossil bones is that a whole bone fossilizes even down to the microscopic size,” Woodward explained. “We can infer growth rate, age (and) maturity level.”
The scientists cut incredibly thin slices from the bone samples and analyzed them under advanced microscopes. The size of the blood vessel gaps indicated that the two dinosaurs were in the stage of rapid growth when they died. If they had been adults, the vascularization would not have been so visible.
We Don’t Much About Dinosaurs’ Growth Process
The researchers could also count the growth rings on every specimen’s bones and were able to estimate their age; Jane was determined to be 13 years old, and Petey 15 years old.
The paper helps scientists’ understanding of the 20-year time between a dinosaur’s hatching and its adulthood. Jane, who was determined to have weighed a ton, apparently died before attaining the stage of gradually rapid growth that usually would have ended up in her gaining approximately 10 tons.
“Everyone loves T. rex, but we don’t really know much about how it grew up,” Woodward said. “It’s probably the most famous dinosaur in the world, and we mostly just have really large skeletons of it.”
This is partly because of the collectors’ obsession and the wide public discovering and showing off the most gigantic T. rex skeleton ever found; oftentimes dug to the disadvantage of smaller exemplars.
Unluckily, only about five to seven fossils of young T. rex dinosaurs have been discovered, and some of those are, in fact, private collections and cannot be analyzed by researchers.