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

Abstract

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.