Abstract: Caninophyllum Lewis, 1929 was widely developed in Europe, Asia and North America from the Carboniferous to the Early Permian, characterized by shortened cardinal septum and no axial structure after early neanic stage. There are disputes about the definition of Caninophyllum Lewis, 1929 due to the main and cardinal septum characteristics and axial structure of some species of this genus in mature growth stages are inconsistent with the original definition. According to ontogenetic characteristics of the well-preserved individuals of Caninophyllum shuangjingziense Zeng, 1983 and Caninophyllum yui Wang, 1989 collected from Shiqiantan Formation of Upper Carboniferous, based on the type species and original description, it is believed that the axial septum of Caninophyllum Lewis, 1929 in the early stages was separated to the cardinal and the counter septa. Axial septum only present during early neanic growth stage, moreover, in mature growth stage the cardinal septum is shortened, the length of counter septum is equal to average counter septa.