Coilopoceratidae is a family of generally large, proper ammnites with strongly involute shells from the Upper Cretaceous, Turonian and Coniacian stages. Coilopoceratids have variably compressed shells with flattish to broadly rounded sides and narrowly rounded to sharp keel-like venters. Whorl sections are generally lanceolate. The suture is ammonitic with an overall clumpy appearance. The Coilopoceratidae are derived from the Tissotiidae by a secondary re-development of an ammonitic suture and of more narrowly compressed shells.