"Adelophthalmus" became the most common of all late Paleozoic eurypterids, existing in greater number and diversity than surviving stylonurines, and diversified in the absence of other eurypterines. Out of the 33 species referred to "Adelophthalmus", 23 (69%) are from the Carboniferous alone. The genus reached its peak diversity in the Late Carboniferous. Though "Adelophthalmus" had already been relatively widespread and represented around all major landmasses in the Late Devonian, the amalgamation of Pangaea into a global supercontinent over the course of the last two periods of the Paleozoic allowed "Adelophthalmus" to gain an almost worldwide distribution.