[2] Of their length, about 25% to 50% is made up by the stipe (the stalk of the leaf, below the blade), which is shiny or sometimes glaucous and round, hairless, and reddish-brown to dark purple or black in color.

[1] Each blade bears 6 to 9 pairs of pinnae, borne alternately or nearly oppositely on the rachis,[1] with an acute (pointed) tip.

Fertile segments often fold along their long axis, giving them a sagittate (arrowhead-like) shape.

[4] The epithet pulchellus means "small and beautiful"[5] and presumably reflects the aesthetic appeal of the species, which they described as "charmante".

[4] However, that name had already been used in 1836 for a different species, the former Cheilanthes pulchella, by Carl Borivoj Presl, rendering it nomenclaturally illegitimate.

[12] Maxon and Charles Alfred Weatherby placed Pellaea formosa within a group of ferns closely related to Notholaena nivea, but declined to make a nomenclatural transfer until the classification of the cheilanthoids was better understood.

[13] Both Edwin Copeland and Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own.

[1] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. formosa, as part of a program to consolidate the cheilanthoid ferns into that genus.

[1] In Mexico, it grows on dry rocky slopes and in ravines, often on limestone, as well as in thorny scrub.

[1] Most common in similar habitats in Guatemala, it also occurs on hillsides and riverbanks, and in forests and thickets.