Type:— ECUADOR. Without a specific locality, flowered in cultivation at Ecuagenera Orchid Nursery, 4 September 2015, Doucette 0311 (holotype: HA).

Diagnosis: The new form differs from Pleurothallis cardiostola f. cardiostola Reichenbach (1854: 128) in its larger flower and number of veins in the dorsal sepal.

Epiphytic, caespitose herbs; roots 1 mm in diam. The stem 180–260 5 2.5 mm, enveloped by two to three tubular, papery sheaths 10–60 5 2.5 mm. Leaves sessile, cordate, 130–192 5 22–28 mm. Inflorescence fasciculate, protected by an erect, papery sheath, 18 mm long; peduncle 3 5 1 mm, with a tubular bract before the pedicel, 1–2 5 2 mm; pedicel 10 5 1 mm; ovary papillose, 7 5 2 mm, flowers non-resupinate, dorsal sepal broadly ovate, 11-veined, tan, minutely pubescent, 20 5 15 mm; synsepalum round, concave below the middle, similar in colour and texture to the dorsal sepal, 14 5 15 mm; petals lanceolate, similar in colour and texture to the sepals, 14 5 5 mm; lip white suffused with yellow, shiny, heater-shaped, 5 5 4 mm; column white suffused with yellow, with a shiny yellow bilobed stigma, 3 5 3 mm.

Etymology:— From the Latin magnis meaning “large” and the English “drab” meaning a dull brown colour, referring to the large dull sepals.

Notes:— The genus Pleurothallis is one of the largest plant genera including over 500 species (The Plant List 2015). Phylogenetic analyses confirmed the genus to be non-monophyletic (Pridgeon et al. 2001). We hypothesize the new form attributed to Pleurothallis cardiostola to belong to Pleurothallis s.s. based on morphology and the placement of Pleurothallis cardiantha Reichenbach (1876: 15) sister to the type P. ruscifolia (Jacquin 1760: 29) R.Br. in W.T. Aiton (1813: 211) with 100% bootstrap support based on a combined data set including two plastid genes (matK and trnL-F) and a nuclear ribosomal gene (nrITS; Pridgeon et al. 2001).

Although there are morphological characters that easily distinguish the taxon described here from typical Pleurothallis cardiostola we hypothesize that it represents an aberrant individual embedded in P. cardiostola. The individual described here differs in traits that have been documented to vary within the species (Luer 2005) and is not reported from a locality disjunct from reported populations of P. cardiostola (i.e. Caribbean or Atlantic forests of Brazil).

We feel that naming this new form of P. cardiostola brings it to the attention of scientists who can test the taxonomic hypothesis presented here using a molecular systematic approach on individuals representing different populations across the range of P. cardiostola. If the taxon described here is not embedded within P. cardiostola we feel that the number of veins of the dorsal sepal and larger flower size are sufficient to warrant recognition at the rank of species. No forms of Pleurothallis cardiostola are reported by International Plant Names Index (2016) or Luer (2005).