A stegosaur tooth (Dinosauria, Ornithischia) from the Early Cretaceous of southwestern France

Jean-Paul Billon-Bruyat,Joane Pouech,Jean-Michel Mazin

doi:10.1007/s00015-010-0028-y

Abstract

The spotty nature of the terrestrial fossil record for the Mesozoic hinders a more complete understanding of dinosaur diversity. For stegosaurs (Ornithischia), the plated dinosaurs, only a few and fragmentary remains are reported from the Early Cretaceous of Europe. A recent revision concluded that only a partial vertebra of the nomen dubiumCraterosaurus (?Aptian, England) could be considered as stegosaurian. Here we report on a stegosaur tooth from the Early Cretaceous (Berriasian) Purbeckian deposits of Cherves-de-Cognac (Charente), southwestern France. This tiny tooth was examined in detail using microtomography. Comparisons being limited by the rarity of stegosaur tooth rows material (e.g., from the skull of the holotype of Stegosaurus stenops) and dental material, notably from Europe, we observed new material of cf. Stegosaurus armatus and Hesperosaurus mjosi from the Upper Jurassic Morrison Formation of Wyoming (USA). The tooth shows the most similarities to the Late Jurassic genera Stegosaurus and Hesperosaurus, but differs in having a distinctive downwardly arched (V-shaped) cingulum on the ?lingual face (maxillary tooth hypothesis). It is referred to as Stegosauria indeterminate, a medium-sized quadrupedal herbivore that inhabited an emerged land between the Armorican Massif and the Massif Central. This finding is the first evidence of a stegosaur from the Early Cretaceous of France and a welcome addition to the meagre European record of that time. In addition, it is the second stegosaurian tooth crown reported from Europe. The assemblage of ornithischians of Cherves-de-Cognac shares some similarities with that of the Early Cretaceous (Berriasian) of the Purbeck Limestone Group, southern England. The relative rarity of ornithischian osteological remains in both Purbeckian environments suggests that most of these dinosaurs were mainly inhabitants of inland terrestrial palaeoenvironments.

Highlights

The Stegosauria, the plated dinosaurs, are medium to largesized quadrupedal herbivorous ornithischians, with proportionally small heads and tiny teeth, and known with confidence from the Middle Jurassic to the Early Cretaceous (Galton and Upchurch 2004; Maidment et al 2008)
The European stegosaurs are well represented in the Middle–Late Jurassic but their fossil record is poor in the Early Cretaceous
The discovery of a stegosaur tooth in the Berriasian of Cherves-de-Cognac is the first record of this dinosaur group in the Early Cretaceous of France

Summary

Introduction

The Stegosauria, the plated dinosaurs, are medium to largesized quadrupedal herbivorous ornithischians, with proportionally small heads and tiny teeth, and known with confidence from the Middle Jurassic to the Early Cretaceous (Galton and Upchurch 2004; Maidment et al 2008). The Late Jurassic marine regression in Western Europe (Hallam 2001) led to the development of confined environments in this gulf, as evaporitic facies from the region of Cognac (Delfaud and Gottis 1966; Hantzpergue and Lafaurie 1994), until the Berriasian in the Champblanc Quarry. In all likelihood, this stegosaur inhabited an emerged land adjacent to such evaporitic environments. No CHE02.084, stored in the palaeontological collection of the Musee d’Angouleme, Charente, France

Methods

Discussion and conclusions