Small ‘Cousins’ of the Tyrannosaurus Rex May Have Been Its Juveniles

Anyone who’s seen the Jurassic Park movies has a vivid image of the iconic behemoth that once ruled the prehistoric world. The Tyrannosaurus Rex, allegedly, had a close and way smaller cousin called the Nanotyrannus. A recent study of fossils, however, suggests that the pygmy kin of the iconic species may actually have been the same dinosaur, just a younger version of it — a T-Rex teenager of sorts.

The Almighty Tyrannosaurus Rex

Tyrannosaurus Rex
Small ‘Cousins’ of the Tyrannosaurus Rex May Have Been Its Juveniles

The first T-Rex fossil was discovered more than a century ago, in 1902, by fossil hunter Barnum Brown in the Hell Creek Formation (the Montana portion). Paleontologists estimate that the largest T-Rex individuals to roam this earth were over 12 meters long from their snout to the tip of their nails. They weighed over eight tons and had teeth the size of bananas. It’s likely that they lived until the age of 30 or older. Talk about a massive species!

Cousins Turned T-Rex Juveniles

Cousins Turned T-Rex Juveniles
Small ‘Cousins’ of the Tyrannosaurus Rex May Have Been Its Juveniles

Ever since paleontologists found a fossil skull back in 1940 that was half the size of a T-Rex’s but pretty similar in shape and bone characteristics, scientists have believed that the Nanotyrannus was nothing more than a distant, significantly smaller cousin of the Tyrannosaurus Rex. Yet, for more than a decade now, experts have been debating whether these two dinosaurs are indeed separate species or not. The debate started after scientists discovered anatomical similarities between the Nanotyrannus and the T-Rex.

The Answer Is in the Bones

Tyrannosaurus Rex skeleton
Small ‘Cousins’ of the Tyrannosaurus Rex May Have Been Its Juveniles

Paleohistologist Holly Woodward and her colleagues from the Oklahoma State University Center for Health Sciences decided to study the microstructure of the leg bones from the two most recent Nanotyrannus specimens paleontologists uncovered. The team made cross-sections of the fossil’s tibia and femur, the weight-bearing bones of the lower and upper leg. They found the two specimens, called Jane and Petey, were at least 13 and 15 years old at the time of their death. The microscopic structure of the bones hinted that the tissues were in a vigorous growth cycle, which means Jane and Petey hadn’t reached adulthood.

That, paired with other similarities found in the development of the Tyrannosaurus Rex, gives room to believe they belong to the same species. However, it is likely they held a different place in the food chain.