The mushroom genera in the family Entolomataceae collectively contain over 1500 species, the large majority of which are in Entoloma.
For instance several taxa such as Leptonia and Nolanea were defined as independent genera, and are still sometimes used as such, but in recent classifications they have been demoted to being subgenera of Entoloma.
Firstly Clitopilus was found to be a clade embedded within Rhodocybe meaning that to avoid polyphyly these genera have to be merged, and although Clitopilus is much smaller, its name takes precedence and should be used for the combined taxon.
[2] Secondly on further analysis taking account of morphological characteristics, the older genera Clitopilopsis and Rhodophana have been resurrected [3] and a new genus Clitocella has been created.
[5] In spite of these changes Entoloma is an enormous genus, and it is not surprising that attempts have been made to split it up.