The picture above is of a spore belonging to Polypodiaceae, a large family that includes many common ferns. Ferns are present in the fossil record beginning from the Devonian.

Kidney-shaped grains displaying a single elongate scar, or monolete scar, are characteristic of many genera of fern spores. The scar is the product of the spore mother cell splitting into four equivalent reproductive cells along a vertical axis. These cells form the scar as they carry a remnant of the line of commonality when separating.