peer reviewed ; A Comparison between the Kess-kess of Hmar Lakhdad (Emsian, Morocco) and the mud mounds of the Philippeville Anticlinorium (Frasnian, Belgium). The Kess-kess of Hmar Lakhdad are Devonian mud mounds, located SE of Erfoud (Moroccan Antiatlas). Fenestral structures, which are very abundant, occur from the base to the top of most buildups. These structures are classified in two groups: stromatactis s.s. and stromatactoid fenestrae. each of them showing a high morphological variability. These fenestrae look very similar to the structures already described from the Belgian mud mounds. However, their attribution to sponges cannot be demonstrated. Microstromatolifhes, a microbial structure, are common in the Moroccan and Belgian buildups. The numerous sedi-mentological similarities between the two types of mounds allow to assign the facies of the Kess-kess to the coral-crinoidal limestones at the base of the Belgian buildups. This comparison justifies a paleoecological and paleobathy-metrical interpretation of the Moroccan mud mounds.