Claim: Tolumnia (previously known as the "equitant Oncidiums") are small plants with small or absent pseudobulbs (a storage organ found in many epiphytic and terrestrial sympodial orchids) completely covered by leaves, which are triangular or circular in cross section and overlap each other at base to resemble a fan,
Evidence: Previously known as the "equitant Oncidiums", the species were segregated from the mega-genus Oncidium by Guido Braem in 1986. The plants are small, usually epiphytic, with small or absent pseudobulbs completely covered by leaves, which are triangular or circular in cross section and overlap each other at base to resemble a fan. The pseudobulb is a storage organ found in many epiphytic and terrestrial sympodial orchids.