Tyrannosaurus rexKingdom: Animalia
Sub Period: None
Hell Creek Formation
Acquired by: Purchase/Trade
Width: 8 mm
Height: 13 mm
Thickness: 4 mm
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).
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.
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