Skeletonema dohrnii is a diatom. Together with S. marinoi, this species has flattened extremities of the processes of the fultoportulae, which interlock with those of succeeding valves without forming knuckles. It is a species of the genus Skeletonema that can be found in many waters across the globe. In the coastal waters of South Korea, their cell diameters are about 3 to 6 micrometers.