A genuine Tyrannosaurus rex tooth is one of the most sought-after fossils in the world. That demand also attracts mislabelled teeth, heavy restorations and outright casts. Learning to identify a T. rex tooth protects your collection and helps you buy with confidence.
This guide walks through the checks experienced collectors use, from geological age to the shape of the serrations.
Step 1: Check the formation and age
Start with the label, not the tooth. T. rex lived only at the very end of the Cretaceous, roughly 68 to 66 million years ago, in western North America. A genuine T. rex tooth should come from a formation of that age, such as:
- Hell Creek Formation (Montana, North Dakota, South Dakota)
- Lance Formation (Wyoming)
- Frenchman Formation (Saskatchewan) or Scollard Formation (Alberta)
A tooth sold as “T. rex” from Morocco, from the Judith River Formation, or from any rock older than the latest Cretaceous is mislabelled. If a seller cannot tell you the formation at all, treat the identification as unproven.
Step 2: Look at the cross-section
This is the single most useful feature. T. rex teeth are unusually thick for a theropod. Seen from the base or in cross-section, the larger teeth are broad and oval, almost rounded, rather than thin and blade-like.
Most other meat-eating dinosaurs, including raptors, Allosaurus and Carcharodontosaurus, have flattened, knife-like teeth. If the tooth is narrow from side to side, it is unlikely to be an adult T. rex lateral tooth.
The small teeth at the very front of the upper jaw (premaxillary teeth) are different again. They are D-shaped in cross-section, with a flat back surface.
Step 3: Examine the serrations
Use a 10x loupe. T. rex teeth have serrations (denticles) on both the front and back edges (carinae). The denticles are relatively large, chisel-like and fairly even in size along each edge.
The front edge often curves or twists slightly around the tooth rather than running in a straight line. Very fine, tightly packed serrations suggest a different animal.
Step 4: Consider size in context
Adult T. rex teeth are large, and the biggest teeth with roots reached about 30 cm (12 inches). But size alone does not prove anything. Juvenile T. rex teeth are smaller, and large shed crowns from other tyrannosaurs exist in older rocks. Use size together with cross-section, serrations and formation.
Step 5: Rule out the look-alikes
| Tooth | How it differs from T. rex |
|---|---|
| Nanotyrannus | Narrower, more blade-like, with finer serrations; same rocks as T. rex |
| Daspletosaurus / Gorgosaurus | Thinner teeth from older (Campanian) formations |
| Albertosaurus | Thinner teeth; from older Canadian formations |
| Carcharodontosaurus | Flat, blade-like teeth with wrinkled enamel; from Morocco |
| Allosaurus | Flattened, curved teeth; from the Jurassic Morrison Formation |
Nanotyrannus causes the most confusion because it shares the Hell Creek and Lance formations with T. rex. Its teeth are proportionally narrower and more compressed. Many scientists now consider Nanotyrannus a separate small tyrannosaur, though the debate is not completely closed. Compare examples in the Nanotyrannus and other tyrannosaurs categories.
Step 6: Check authenticity and restoration
Even a correctly identified T. rex tooth may be restored. Check the following:
- Enamel. Real enamel has a natural sheen and fine texture. Patches that look painted, glossy or smooth may be restoration.
- Tip and base. These are the most commonly restored areas. Look for colour changes or abrupt texture shifts.
- UV light. Fillers and glues often fluoresce differently from original fossil.
- Weight and feel. A real tooth feels dense and cool; a resin cast feels light and warm.
A reputable seller will describe any repair in writing. Restoration does not make a tooth fake, but it should always be disclosed.
Step 7: Buy from a specialist
The best protection is a dealer with deep experience in tyrannosaur teeth. Buried Treasure Fossils lists the formation, locality and condition of each tooth in its Tyrannosaurus rex collection and guarantees authenticity. Exceptional specimens also appear in museum quality fossils.
Quick checklist
- Formation is latest Cretaceous (Hell Creek, Lance or equivalent)
- Tooth is thick and oval in cross-section
- Serrations on both edges, relatively large and even
- Size fits the specimen’s position and age
- Look-alikes such as Nanotyrannus ruled out
- Restoration disclosed and checked under UV
- Private-land source and authenticity guarantee
Frequently asked questions
1. How can you tell if a T. rex tooth is real?
Check that it comes from a latest Cretaceous formation, is thick and oval in cross-section, and has relatively large serrations on both edges. Then look for restoration under a UV light.
2. What is the difference between a T. rex and a Nanotyrannus tooth?
Nanotyrannus teeth are narrower and more blade-like, with finer serrations, while T. rex teeth are thick and robust.
3. Can a T. rex tooth come from Morocco?
No. T. rex lived only in western North America. Large Moroccan theropod teeth usually belong to Carcharodontosaurus or other African predators.
4. Does restoration mean a T. rex tooth is fake?
No. Restored teeth are real fossils with some repair. The amount of restoration should simply be disclosed.
Identify with confidence
Identifying a T. rex tooth comes down to age, shape, serrations and honesty about condition. Learn these checks, compare plenty of genuine examples and buy from specialists who document every specimen. Start comparing real teeth in the T. rex tooth collection at Buried Treasure Fossils.