Tooth replacement in a specimen of Tyrannosaurus rex (Dinosauria, Theropoda) from the Hell Creek Formation (Maastrichtian), Montana

ABSTRACT

A well-preserved skull of Tyrannosaurus rex from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Montana is used to document its tooth replacement with the help of high-resolution medical CT scanning. A pattern of retaining only one single replacement tooth before replacing the functional tooth is reconstructed for most alveoli of the jaws, with exception of the second alveolus of the left maxilla, and the fourth alveolus of the right dentary, where another, second replacement tooth can be seen. The youngest replacement teeth have only a thin layer of enamel around the tooth crown, the larger replacement teeth have thicker enamel, fortified at the apex as in the functional teeth. The Zahnreihen approach allows to reconstruct a z-spacing of 2 in the upper jaws, whereas the right dentary displays a z-spacing of 1 in the rostral and distal third of the tooth row and a z-spacing of 2 in its medial part. In MB.R.91216, teeth of the upper jaws and the medial part of the dentary were probably replaced in a regular alternating pattern between odd and even teeth, whereas the mesial and distal teeth of the dentary were replaced simultaneously.

KEYWORDS:

• Tyrannosaurus
• CT
• dentition
• tooth replacement
• functional teeth
• z-spacing

Acknowledgments

The authors would like to thank Niels Nielsen and Jens Peter Jensen, the owners of the specimen, for making the skeleton of ‘Tristan Otto’ available for this study. We thank the preparators of the MfN, in particular, Marten Schöle, as well as our irreplaceable collections manager Thomas Schossleitner for help with arranging the specimen for investigations. We are indebted to Patrick Asbach and his team for providing the CT scanner for this study and discussing the specimen with us. Thanks also goes to Dr Heinrich Mallison and Dr Matteo Belvedere, who have spent a lot of time and effort to photograph each skull fragment and have made them available. FS thanks Prof. Jens Rolff, Dr Oliver Hampe and Ms Amy Wiseman for their thorough comments and advices in her MSc thesis. The authors thank cordially two anonymous referees whose thorough comments helped us significantly to improve the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

All CT scans are fully available under the following DOI:https://dx.doi.org/10.7479/bkz4-3b42.

Data deposition

The data will be deposited at the server of the Museum fuer Naturkunde Berlin and accessible under the following DOI: https://dx.doi.org/10.7479/bkz4-3b42