Vermilacinia johncasadyi is a rare fruticose lichen, found on rocks along the Pacific Coast of Baja California peninsula on Punta Cono, and directly westward across the ocean on Cedros Island.

[1] Vermilacinia johncassadyi is classified in the subgenus Vermilacinia, distinguished from related species by its thallus divided into strap-like branches arising from a blackened base to about ¼ the way up the branches, and by producing lichen substances of triterpenes referred to as T1 and T2 in reference to their Rf class on thin-layer chromatography plates.

It differs in its lichen substances (contains T3, not T1 and T2), and development of its apothecia elevated from the branch by a short narrower stalk-like lobe, in contrast to apothecia in V. johncassadyi that appear to pinch off from the branch margins, occurring in aggregate and often not fully developed, the margins notably wavy as a result.

He, and his graduate student, Thomas McCloud, had accompanied Richard Spjut on an expedition to Baja California during May 1986 for the collection of plant and lichen samples in search of new chemical compounds for treating cancer.

Vermilacinia johncasadyi was first discovered along the northwest coast of Cedros Island on vertical rock faces about 500 feet directly above the ocean, 12 April 1989, and described as a new species in 1996 (Spjut & Marin 10535, holotype US)[1][2] Peter Bowler and Janet Marsh in 2004 indicated that Vermilacinia johncasadyi was an "aberrant insular" form of Vermilacinia laevigata (synonym Niebla laevigata[3]) They further implied that V. johncassadyi has the same lichen substances as V. laevigata in making reference to the triterpene T3.