Juvenile Tyrannosaurus rex Tooth

Taxonomy

Tyrannosaurus rex

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Avetheropoda
Family: Tyrannosauridae
Genus: Tyrannosaurus
Species: Tyrannosaurus rex
Author Citation Osborn, 1905

Geological Time Scale

Eon: Phanerozoic
Era: Mesozoic
Period: Cretaceous
Sub Period: None
Epoch: Late

Stratigraphy

Hell Creek Formation

Provenance

Acquired by: Purchase/Trade

Dimensions

Width: 8 mm
Height: 13 mm
Thickness: 4 mm

Location

Garfield County
Montana
United States

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• hell creek
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Comments

Identification:

This tooth was sold as being from a Dromaeosaur. The serrations' shape and their similarity on both carinae say otherwise. 

In the Hell Creek Formation, there are potentially two Tyrannosaur species. If Nanotyrannus is invalid, then this is automatically a T. rex tooth. For those who consider Nanotyrannus to be valid, this tooth is still T. rex based on the robustness of the tip and serrations, and the CHR (Crown Height Ratio). Tyrannosaurus maxillary teeth may still have minor basal compression, as this one does.

This is from a juvenile animal based on its small size and feeding wear (thus it's not a germ tooth).

Thanks to @Troodon and @hxmendoza for their help with identification. I also contacted Christophe Hendrickx, who also said it was from a young T. rex.

Other:

Mesial Serration Density: ~ 4 serrations / mm.

Distal Serration Density: ~ 4 serrations / mm.

Note: Serration density alone is not an identifying feature of Tyrannosaur teeth this small.

This tooth is from the right maxilla based on the wear on the lingual face. Feeding wear is also visible on some of the serrations.

Citation:

OSBORN, HENRY, 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs, Bulletin of the AMNH, Volume 21, Article 14, Pages 259-265, https://digitallibrary.amnh.org/handle/2246/1464