Vermilacinia pumila is distinguished from V. procera by its relatively small thallus composed of stubby basal branches not more than 1 cm high.

[1] The genus Vermilacinia was distinguished from Niebla by the absence of longitudinal organization of hyphal cells within the medulla into chondroid strands, and by the secondary metabolites (lichen substances) primarily terpenes that include the triterpene zeorin, the diterpenes (-)-16 α-hydroxykaurane, an unidentified triterpene, referred to as T3, and the aliphatic depside, bourgeanic acid.

[4] Peter Bowler with coauthor Janet Marsh in the Lichen Flora of the Greater Sonoran Desert[1][5] stated that "there are no generic differences between it [Vermilacinia] and Niebla."

In support of their conclusion they stated that "none of the earlier studies[6] proposed separating groups at the generic level within Niebla," and that in a 1976 presentation he (Bowler) concluded that the hyphal aggregation embedded in the medulla of some of the larger rock and sand inhabiting forms of N. homalea and N. josecuervoi were not of generic significance, and noted that medullar hyphae in all species adhered to one degree or another."

Bowler and Marsh further stated that "chemistry is not a basis for separating Vermilacinia from Niebla, because it seems, as they say, there exists a "diversity of chemical races" without "apothecial, spore or pycnidial, or conidial differences."

Richard Spjut, in a manuscript submitted for peer review in 1990, and also in a presentation to the American Bryological and Lichenological Society that same year,[9] indicated that he had recognized 50 species in Niebla and Vermilacinia.