1. Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, CNRS UMR 6046, Faculté des Sciences, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France
2. Peabody Museum, Harvard University, 11 Divinity Avenue, Cambridge, Massachusetts 02138, USA
3. Université de N'Djamena, BP 1117, N'Djamena, Tchad
4. Anthropologisches Institut/MultiMedia Laboratorium, Universität Zürich-Irchel, Winterthurerstrasse 190, 8057 Zürich, Switzerland

Correspondence to: Michel Brunet¹ Correspondence and requests for materials should be addressed to M.B. (Email: michel.brunet@univ-poitiers.fr).

Abstract

Discoveries in Chad by the Mission Paléoanthropologique Franco-Tchadienne have substantially changed our understanding of early human evolution in Africa^{1, 2, 3}. In particular, the TM 266 locality in the Toros-Menalla fossiliferous area yielded a nearly complete cranium (TM 266-01-60-1), a mandible, and several isolated teeth assigned to Sahelanthropus tchadensis ³ and biochronologically dated to the late Miocene epoch (about 7 million years ago). Despite the relative completeness of the TM 266 cranium, there has been some controversy about its morphology and its status in the hominid clade^{4, 5}. Here we describe new dental and mandibular specimens from three Toros-Menalla (Chad) fossiliferous localities (TM 247, TM 266 and TM 292) of the same age⁶. This new material, including a lower canine consistent with a non-honing C/P₃ complex, post-canine teeth with primitive root morphology and intermediate radial enamel thickness, is attributed to S. tchadensis. It expands the hypodigm of the species and provides additional anatomical characters that confirm the morphological differences between S. tchadensis and African apes. S. tchadensis presents several key derived features consistent with its position in the hominid clade close to the last common ancestor of chimpanzees and humans.

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