The callosomarginal artery is a terminal branch of the ACA, which bifurcates with the pericallosal artery. This artery in turn branches into the medial frontal arteries (anterior, intermediate, posterior), and the paracentral artery, with the cingulate branches arising throughout its length.
Depending on anatomical variation, the callosal marginal artery may be none discrete or not be visible. In the latter case, the branches mentioned will originate from the pericallosal artery. In a study of 76 hemispheres, the artery was present in only 60% of the cases. Angiography studies cite that the vessel can be seen 67%  or 50% of the time.
Note that the definition and differences between callosomarginal arteryr and pericallosal artery is not clear between sources, especially between gross anatomy and angiographic anatomy. In angiography or for Rhoton et al. in microsurgical surgery, the callosomarginal artery cannot really be defined in term of a given group of vessels that arise from it because any of the usual branches of the callosamarginal artery may arise directly from the pericallosal artery. Because of this variablity, they prefer to define it as: "the artery that courses in or near the cingulated sulcus and gives origin to "two or more cortical branches"".
Microsurgical anatomy of the distal anterior cerebral artery. Perlmutter D, Rhoton AL Jr. - J Neurosurg. 1978 Aug;49(2):204-28.