Xylobium elongatum (Lindl. & Paxton) Hemsl., Biol. Cent.-Amer., Bot. 3: 252. 1884.
Type: Guatemala. Without locality, G.U. Skinner s.n. (holotype: K-L).
Illustrated specimen: Colombia. Chocó: Municipality of Unguía, “Expedición COLOMBIA BIO Cerro Tacarcuna”. 1200 m. 2 April 2017. E. Dominguez et al. 900 (HUA; LCDP voucher).
Etymology: From Latin e- “extension or dilation” and longus, longa, longum “long”, in reference to the shape of the pseudobulbs of this species.
Xylobium elongatum is a widely distributed species that ranges from Mexico to Peru. It is easily distinguished from other Xylobium by the conspicuously slender, elongated, cylindrical pseudobulbs bearing two leaves. The pseudobulbs of Xylobium pallidiflorum (Hook.) G.Nicholson are also elongate, but are much smaller and bear a single leaf. The whitish-cream flowers are similar to several other species in the genus, including X. leontoglossum (Rchb. f.) Rolfe and X. variegatum (Ruiz & Pav.) Garay & Dunst. However, Xylobium elongatum may be distinguished by the mid-lobe of the lip that is longer than the lateral lobes and the less prominent callus with a conspicuously papillose, conduplicate apex.