Download the full-sized PDF of Variation in premaxillary tooth count and a developmental abnormality in a tyrannosaurid dinosaurDownload the full-sized PDF



Permanent link (DOI):


Export to: EndNote  |  Zotero  |  Mendeley


This file is in the following communities:

Biological Sciences, Department of


This file is in the following collections:

Journal Articles (Biological Sciences)

Variation in premaxillary tooth count and a developmental abnormality in a tyrannosaurid dinosaur Open Access


Author or creator
Miyashita, T.
Tanke, D. H.
Currie, P. J.
Additional contributors
Tooth count
Development regulation
Dinosaur Park Formation
Type of item
Journal Article (Published)
Premaxillary tooth count tends to be stable amongst toothed dinosaurs, and most theropods have four teeth in each premaxilla. Only one case of bilaterally asymmetric variation is known in theropod premaxillary dentition, and there is no record of ontogenetic or individual variation in premaxillary tooth count. Based on these observations, a tyrannosaurid left premaxilla with three teeth (TMP 2007.20.124) is an interesting deviation and represents an unusual individual of Daspletosaurus sp. with a developmental abnormality. The lower number of teeth is coupled with relatively larger alveoli, each of which is capable of hosting a larger than normal tooth. This indicates that tooth size and dental count vary inversely, and instances of reduction in tooth count may arise from selection for increased tooth size. On the other hand, the conservative number of premaxillary teeth in most theropods implies strong developmental constraints and a functional trade-off between the dimensions of the premaxillary alveolar margin and the size of the teeth. In light of recent advances in the study of tooth morphogenesis, tooth count is a function of two parameters: dimensions of an odontogenic field for a tooth series, and dimensions of tooth positions. A probable developmental cause for the low tooth count of TMP 2007.20.124 is that the dimensions of the alveoli expanded by approximately a third during tooth morphogenesis. Numerical traits such as tooth count are difficult to treat in a phylogenetic analysis. When formulating a phylogenetic character, a potential alternative to simply counting is to rely on the morphological signature for developmental parameters that control the number of the element in question.
Date created
License information
© 2010 Polish Academy of Sciences, Institue of Paleobiology. This version of this article is open access and can be downloaded and shared. The original author(s) and source must be cited.
Citation for previous publication
Miyashita, T., Tanke, D.H., and Currie, P.J. (2010). Variation in premaxillary tooth count and a developmental abnormality in a tyrannosaurid dinosaur. Acta Palaeontographica Polonica, 55: 635-643. doi:

Link to related item

File Details

Date Uploaded
Date Modified
Audit Status
Audits have not yet been run on this file.
File format: pdf (Portable Document Format)
Mime type: application/pdf
File size: 290658
Last modified: 2015:10:12 14:52:50-06:00
Filename: APP_55_2010_635.pdf
Original checksum: 6d722b4073ac438364b0720b3b87cb52
Well formed: true
Valid: true
File title: Miyashita_20090067.vp
File author: Instytut
Page count: 9
Activity of users you follow
User Activity Date