On Acanthostomum gymnarchi (Dollfus, 1950), with notes on the genera Acanthostomum Looss, 1899, Atrophocaecum Bhalerao, 1940, Gymnatotrema Morosov, 1955 and Haplocaecum Simha, 1958.

1. Acanthostomum gymnarchi (Dollfus, 1950) is redescribed and the atrophy of the right caecum and the presence of an anal pore at the end of the left caecum were observed in this species. 2. The genera Atrophocaecum Bhalerao, 1940; Gymnatotrema Morosov, 1955; and Haplocaecum Simha, 1958 are considered synonyms of the genus Acanthostomum Looss, 1899 which is here divided into four subgenera. 3. Acanthostomum bagri Thomas, 1958 is considered a synonym of A. absconditum (Looss, 1901). 4. A key to the five species of Acanthostomum found in the Sudan is provided.