A Tiny Throat Bone Just Proved Nanotyrannus Was Its Own Dinosaur Species
For most of the past few decades, Nanotyrannus had an identity problem. The dinosaur — whose name means "dwarf tyrant" — was first described as its own species back in 1988, but many scientists kept insisting it was really just a young, still-growing Tyrannosaurus rex. The debate dragged on for so long that it became one of paleontology's most stubborn unsolved arguments. Now, researchers from Princeton University and the University of Nebraska have published a study in the journal Science that offers what may be the strongest evidence yet: Nanotyrannus was a real, distinct species, and it lived at the same time and in the same environment as its much larger relative.
The key to cracking this mystery came from an unexpected place — a tiny bone in the animal's throat called the hyoid (HY-oid) bone. This small, delicate bone sits at the base of the tongue and helps with swallowing and vocalizing. In most dinosaur studies, scientists focus on larger, sturdier bones like femurs (thigh bones) or ribs when they want to figure out how old an animal was when it died. But the hyoid bone had been preserved alongside the original Nanotyrannus skull at the Cleveland Museum of Natural History, and the research team decided to examine it closely using a technique called bone histology — the microscopic study of bone tissue structure. Think of it like slicing a very thin cross-section of the bone and reading the growth rings inside, similar to how you can count the rings in a tree stump to determine the tree's age.
What the researchers found inside that tiny bone changed everything. The growth patterns in the hyoid indicated that the animal was at or near full maturity when it died — it was not a juvenile on its way to becoming a giant. Ashley Poust, a paleontologist at the University of Nebraska State Museum, explained that the bone showed clear signals of maturity, meaning the animal had reached its adult size. Since Nanotyrannus was only about 18 feet long — compared to a T. rex that could exceed 40 feet — this size difference could not be explained by age alone. The two animals were simply built differently, making them separate species.
To make sure the hyoid bone was actually a reliable growth indicator, Poust compared it to hyoid bones from living relatives of dinosaurs, including ostriches, alligators, and lizards. The growth signals were consistent across all of these animals, which gave the team confidence that what they saw in the Nanotyrannus fossil was not a fluke. This was also the first time this approach had been applied to dinosaur fossils, which means the method itself is a new tool that paleontologists can use to study other fragmentary or incomplete remains in the future.
The original Nanotyrannus skull has a long and winding history. It was first discovered in 1942 and was initially classified as a completely different dinosaur called Gorgosaurus. Decades of re-examination followed, and in 1988, scientists gave it the name Nanotyrannus lancensis. But the debate never truly settled — many researchers argued the skull simply looked different from T. rex because it belonged to a younger animal, and that as it aged, it would have grown into something much bigger. The new hyoid evidence directly challenges that idea, and it follows closely on another recent study published in the journal Nature that examined a different possible Nanotyrannus specimen found in Montana.
These findings raise fascinating new questions about how dinosaur ecosystems actually worked. If Nanotyrannus and T. rex lived side by side, that means a single environment supported at least two large meat-eating predators at the same time. This kind of complexity is something scientists are still working to understand — how did multiple apex predators, animals near the top of the food chain, coexist without completely competing each other out of existence? The answer likely involves differences in prey, hunting behavior, and habitat use, and it adds a whole new layer to how scientists reconstruct the lost world of the Late Cretaceous period, the final chapter of the dinosaur age. The fossil record, it turns out, still has plenty of surprises left to offer.
Source: ScienceDaily