Paul C. Sereno, ^1* Allison L. Beck, ¹ Didier B. Dutheil, ² Hans C. E. Larsson, ¹ Gabrielle H. Lyon, ³ Bourahima Moussa, ⁴ Rudyard W. Sadleir, ⁵ Christian A. Sidor, ¹ David J. Varricchio, ⁶ Gregory P. Wilson, ⁷ Jeffrey A. Wilson ⁸

Lower Cretaceous fossils from central Niger document the succession of sauropod dinosaurs on Africa as it drifted into geographic isolation. A new broad-toothed genus of Neocomian age (~135 million years ago) shows few of the specializations of other Cretaceous sauropods. A new small-bodied sauropod of Aptian-Albian age (~110 million years ago), in contrast, reveals the highly modified cranial form of rebbachisaurid diplodocoids. Rates of skeletal change in sauropods and other major groups of dinosaurs are estimated quantitatively and shown to be highly variable.

¹ Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57 Street, Chicago, IL 60637, USA.
² Laboratoire de Paléontologie-EPHE-Muséum National d'Histoire Naturelle, 8 rue du Buffon, 75005 Paris, France.
³ Project Exploration, 5521 South Blackstone Avenue, Chicago, IL 60637, USA.
⁴ Centre des Sciences de la Terre, Centre National de Recherche Scientifique, 6 Boulevard Gabriel, 2100 Dijon, France.
⁵ Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607, USA.
⁶ Museum of the Rockies, Montana State University, Bozeman, MT 59717, USA.
⁷ University of California, Museum of Paleontology, 1101 Valley Life Sciences Building, Berkeley, CA 94720, USA.
⁸ Museum of Paleontology, University of Michigan, 1109 Geddes Road, Ann Arbor, MI 48109, USA.
^*   To whom correspondence should be addressed. Successive authors are listed alphabetically.