The Proterocameroceratidae were the first of the Endocerida. They began early in the Ordovician with Proendoceras or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor. The Proterocameroceratidae ultimately suffered the extinction at the end of the Ordovician, but not before having given rise to a variety of endocerid families. They remain a subject of interesting research.