Zygopetalum, reduce petals.

[MCSchrum]

I have a Zygo 'Advance Australia' that has been blooming faithfully for a couple years. It is currently in bloom, however, one of the flowers is particularly strange. This flower has only two petals, two sepals, and a column, but no lip. It's very peculiar. Is there a name for this condition? Is this common in certain types of orchids?

[coeruleo]

some orchids will have a deformed flower sometimes. some are more prone to it. i have a bollopetalum hybrid that has deformed flowers often. petals merged, missing, missing lips sometimes.