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Simosuchus clarki is a bizarre, pug-nosed notosuchian crocodyliform known only from the Upper Cretaceous (Maastrichtian) Maevarano Formation in the Mahajanga Basin of northwestern Madagascar. When originally named and described in 2000, S. clarki was based entirely on a single specimen that included a nearly complete skull and lower jaw preserved in articulation with the anterior and mid-trunk portions of the postcranial skeleton, as well as several associated elements from the posterior region. The species is now represented by three additional partial and nearly complete articulated skeletons, as well as numerous isolated elements (mostly teeth), that permit detailed description of its entire bony anatomy, the primary subject of other chapters in this volume. These specimens were discovered as part of the ’Mahajanga Basin Project,’ initiated in 1993 and conducted jointly by Stony Brook University and the Universite d’Antananarivo, in the Berivotra and Masiakakoho study areas. The best-preserved specimens of S. clarki were entombed in massive, poorly sorted, clay-rich debris flow deposits (facies 2 of the Anembalemba Member) that accumulated in channel belts in response to exceptional rainfall events. Simosuchus, along with its contemporaries in the Maevarano assemblage, lived in a strongly seasonal, semi-arid climate some 20 million years after Madagascar separated from the India/Seychelles block and became an island isolated in the Indian Ocean.