[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

High Tooth Replacement Rates in Sauropod Dinosaurs



From: Ben Creisler
bcreisler@gmail.com

New in PLoS ONE:


Michael D. D’Emicl, John A. Whitlock , Kathlyn M. Smith, Daniel C.
Fisher & Jeffrey A. Wilson (2013)
Evolution of High Tooth Replacement Rates in Sauropod Dinosaurs.
PLoS ONE 8(7): e69235.
doi:10.1371/journal.pone.0069235
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0069235


Background

Tooth replacement rate can be calculated in extinct animals by
counting incremental lines of deposition in tooth dentin. Calculating
this rate in several taxa allows for the study of the evolution of
tooth replacement rate. Sauropod dinosaurs, the largest terrestrial
animals that ever evolved, exhibited a diversity of tooth sizes and
shapes, but little is known about their tooth replacement rates.

Methodology/Principal Findings

We present tooth replacement rate, formation time, crown volume, total
dentition volume, and enamel thickness for two coexisting but
distantly related and morphologically disparate sauropod dinosaurs
Camarasaurus and Diplodocus. Individual tooth formation time was
determined by counting daily incremental lines in dentin. Tooth
replacement rate is calculated as the difference between the number of
days recorded in successive replacement teeth. Each tooth family in
Camarasaurus has a maximum of three replacement teeth, whereas each
Diplodocus tooth family has up to five. Tooth formation times are
about 1.7 times longer in Camarasaurus than in Diplodocus (315 vs. 185
days). Average tooth replacement rate in Camarasaurus is about one
tooth every 62 days versus about one tooth every 35 days in
Diplodocus. Despite slower tooth replacement rates in Camarasaurus,
the volumetric rate of Camarasaurus tooth replacement is 10 times
faster than in Diplodocus because of its substantially greater tooth
volumes. A novel method to estimate replacement rate was developed and
applied to several other sauropodomorphs that we were not able to thin
section.

Conclusions/Significance

Differences in tooth replacement rate among sauropodomorphs likely
reflect disparate feeding strategies and/or food choices, which would
have facilitated the coexistence of these gigantic herbivores in one
ecosystem. Early neosauropods are characterized by high tooth
replacement rates (despite their large tooth size), and derived
titanosaurs and diplodocoids independently evolved the highest known
tooth replacement rates among archosaurs.