Dendrobium tetrapterum, a cryptic species in the D. lindleyi alliance (Orchidaceae; Dendrobiinae): evidence from morphological and molecular data

Dendrobium tetrapterum, a cryptic species in the D. lindleyi alliance, is described and illustrated. Detailed morphological comparisons indicate that it is similar to D. lindleyi and D. jenkinsii but can be distinguished by four morphological characters, namely petals without (vs. with) claw, slit (vs. entire) transverse septum at lip base, anther cap with (vs. without) indentation on each side and a rhombic (vs. pentagonal–octagonal or oblong) pseudobulb cross-section. Combined with the geographical distribution and whole plastid genome data, we confirm that D. tetrapterum is not a natural hybrid of the other two species, but a separate species.