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Title: Tooth counts through growth in diapsid reptiles: implications for interpreting individual and size-related variation in the fossil record
Contributor(s): Brown, Caleb Marshall (author); VanBuren, Collin S (author); Larson, Derek W (author); Brink, Kirstin S (author); Campione, Nicolas E  (author)orcid ; Vavrek, Matthew J (author); Evans, David C (author)
Publication Date: 2015-04
Early Online Version: 2015-02-16
Open Access: Yes
DOI: 10.1111/joa.12280Open Access Link
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Abstract: Tooth counts are commonly recorded in fossil diapsid reptiles and have been used for taxonomic and phylogenetic purposes under the assumption that differences in the number of teeth are largely explained by interspecific variation. Although phylogeny is almost certainly one of the greatest factors influencing tooth count, the relative role of intraspecific variation is difficult, and often impossible, to test in the fossil record given the sample sizes available to palaeontologists and, as such, is best investigated using extant models. Intraspecific variation (largely manifested as size‐related or ontogenetic variation) in tooth counts has been examined in extant squamates (lizards and snakes) but is poorly understood in archosaurs (crocodylians and dinosaurs). Here, we document tooth count variation in two species of extant crocodylians (Alligator mississippiensis and Crocodylus porosus) as well as a large varanid lizard (Varanus komodoensis). We test the hypothesis that variation in tooth count is driven primarily by growth and thus predict significant correlations between tooth count and size, as well as differences in the frequency of deviation from the modal tooth count in the premaxilla, maxilla, and dentary. In addition to tooth counts, we also document tooth allometry in each species and compare these results with tooth count change through growth. Results reveal no correlation of tooth count with size in any element of any species examined here, with the exception of the premaxilla of C. porosus, which shows the loss of one tooth position. Based on the taxa examined here, we reject the hypothesis, as it is evident that variation in tooth count is not always significantly correlated with growth. However, growth trajectories of smaller reptilian taxa show increases in tooth counts and, although current samples are small, suggest potential correlates between tooth count trajectories and adult size. Nevertheless, interspecific variation in growth patterns underscores the importance of considering and understanding growth when constructing taxonomic and phylogenetic characters, in particular for fossil taxa where ontogenetic patterns are difficult to reconstruct.
Publication Type: Journal Article
Source of Publication: Journal of Anatomy, 226(4), p. 322-333
Publisher: Wiley-Blackwell Publishing Ltd
Place of Publication: United Kingdom
ISSN: 0021-8782
Field of Research (FOR): 060807 Animal Structure and Function
040308 Palaeontology (incl. Palynology)
060301 Animal Systematics and Taxonomy
Socio-Economic Objective (SEO): 970106 Expanding Knowledge in the Biological Sciences
970104 Expanding Knowledge in the Earth Sciences
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article
School of Environmental and Rural Science

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