Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from Southern France

Pascal Godefroit,Bernard Gomez,Géraldine Garcia,Xavier Valentin,Aude Cincotta,Koen Stein,Ulysse Lefèvre

doi:10.1038/s41598-017-13160-2

Abstract

Rhabdodontidae is a successful clade of ornithopod dinosaurs, characteristic of Late Cretaceous continental faunas in Europe. A new rhabdodontid from the late Campanian, of southern France, Matheronodon provincialis gen. et sp. nov., is characterized by the extreme enlargement of both its maxillary and dentary teeth, correlated to a drastic reduction in the number of maxillary teeth (4 per generation in MMS/VBN-02-102). The interalveolar septa on the maxilla are alternately present or resorbed ventrally so as to be able to lodge such enlarged teeth. The rhabdodontid dentition and masticatory apparatus were adapted for producing a strict and powerful shearing action, resembling a pair of scissors. With their relatively simple dentition, contrasting with the sophisticated dental batteries in contemporary hadrosaurids, Matheronodon and other rhabdodontids are tentatively interpreted as specialized consumers of tough plant parts rich in sclerenchyma fibers, such as Sabalites and Pandanites.

Highlights

Rhabdodontids are basal iguanodontian dinosaurs and characteristic elements of Late Cretaceous dinosaur faunas in Europe[1,2,3,4]
Rhabdodontid ornithopod characterized by the following autapomorphies: enlargement of both maxillary and dentary teeth; reduction of maxillary tooth families (4 per generation in MMS/VBN-02-102); interalveolar septa on the maxilla alternately present or resorbed ventrally, so that one functional tooth is lodged in two paired alveoli; shortened rostral process on the maxilla; broad dorsal shelf along the rostral third of the maxilla; more than 25 vertical and parallel ridges on the labial side of the maxillary teeth
Besides Matherodon provincialis, three rhabdodontid genera and six species have currently been named: Rhabdodon priscus from the Campanian-Maastrichtian of France and Spain[1], R. septimanicus from the Campanian-Maastrichtian of France[2], Zalmoxes robustus and Z. shqiperorum from the Maastrichtian of Romania[3,17], Mochlodon suessi from the Campanian of Austria[18], and Mochlodon vorosi, from the Santonian of Hungary[4]

Summary

Tooth microstructure

A coronal section in a maxillary tooth (Fig. 4) shows a jagged pattern of ridges and grooves on the labial surface (Fig. 4b,h), corresponding to the numerous vertical ridges, and a rather smooth surface on the lingual side. Measurements of enamel thickness (Supplementary Table S1) demonstrate that the ridges on the labial side of the crown have thicker enamel than the grooves in between. Unlike in hadrosaurids[14], the enamel is present around the entire crown of unworn teeth, but thinner on the lingual side of the sectioned specimen. Measurements on a well-preserved side of the tooth (Fig. 4c) show that Matheronodon has significantly thicker (Supplementary Table S1; independent t-test, N = 11, p < 0.001) enamel The dentine of the sectioned tooth (Fig. 4d,e) does not show any clear variation in the orientation of dentine tubules as in hadrosaurids[14]. We could observe a high number of incremental Von Ebner lines (50 to 100 IVELs, Fig. 4e), indicating a long development time for a single tooth[15]. The preservation state of the tooth did not allow a precise count of Von Ebner lines in the dentine

Discussion

Methods

Author Contributions

Findings

Additional Information