Nanotyrannus is a unique and hotly debated classification for a series of small tyrannosaurid fossils. These fossils closely resemble the Tyrannosaurus Rex, but there are enough differences in the size and tooth count to call into question whether they are the same species.

Some paleontologists have put forth that Nanotyrannus is its own group of smaller dinosaurs, while others argue it is a juvenile T. Rex that has not yet reached its full size. While there are compelling arguments from both sides, a uniform understanding has not yet been reached. This is due to the small sample size of skeletal fossils, since the Tyrannosaurids like this are quite rare.

This specimen is a Nanotyrannus tooth discovered on private land in the Hell Creek Formation. It is dated to over 66,000,000 years old and still contains serration patterns that the animal had in life.

We've chosen to use the name Nanotyrannus for this specimen to bring attention to the ongoing paleontological debate and remind us how our understanding of the prehistoric past is still changing as new science is discovered.

The tooth is carefully packaged in within a glass-topped riker display case. The case measures 4"x3"x1" and is shipped with an informational photo card along with a certificate of authenticity.

We have several Nanotyrannus and Tyrannosaurus tooth fossils available based on size. You can see all the fossil in our collection below.

Our understanding of dinosaurs is constantly changing. Every day, we learn more about these prehistoric beasts and the ways they looked, moved, and lived. While some may have a fixed picture in their heads of what life was like 100 million years ago, there is still much to discover and many questions to resolve.

Nanotyrannus is a perfect example of this changing understanding. It's a tricky little fossil that still has scientists stumped to this day. Its name harkens to the Tyrannosaurus Rex, which is the source of much debate. One camp has it that Nanotyrannus is a simply a juvenile version of the T. Rex, while the other says there’s enough anatomical differences to classify it as a different species entirely. The scarcity of Nanotyrannus fossils makes this debate difficult to resolve.

Nanotyrannus was named in 1988 when a Gorgosaurus lancensis skull was reclassified as a different species. Research headed up by paleontologist Robert T. Bakker found that despite the skull’s resemblance to a small T. Rex, it had fused bones, suggesting the animal had grown into maturity and was thus not a juvenile. Supporters of this camp also point to differences in tooth count, the shape of the animal’s snout, and size of the skull cavity. This would seem to show that Nanotyrannus was its own species.

Conversely, other scientists have it that these differences are not enough to account for Nanotyrannus as a different species, given the small sample size of available fossils. In this model, differences in Nanotyrannus and T. Rex can be explained through the individuals' size variations as opposed to age differences. A smaller skull may just belong to a smaller member of the species, rather than a younger member or an entirely different dinosaur. This has the potential to account for the bone fusion, the main characteristic cited to support Nanotyrannus being a separate species.

When comparing the body structures of a Tyrannosaurus and Nanotyrannus side by side, we can see the latter is more slender, with larger arms proportional to their body and more teeth. However, some research has also shown that the discovered Nanotyrannus specimens were not finished growing. To some, this is evidence that the Nanotyrannus was just a growing T. Rex— others think it would have just become a larger Nanotyrannus.

The paleontological debate on Nanotyrannus continues to this day. Unless more complete fossils of the dinosaur are discovered though, the small sample size will continue to be inconclusive. 

This debate on Nanotyrannus's origins is a telling microcosm of dinosaur paleontology: we can know quite a lot about dinosaurs from their bones, but there will always be questions. We've chosen to use the Nanotyrannus name here to bring reference to this taxonomic conundrum and keep in mind the ever changing world of paleontological science.

This specimen is a Nanotyrannus fossil tooth recovered on private land in the Hell Creek formation. It is estimated to be over 66 million years old and still contains detailed serrations from the original tooth.