Some suggested that this species may be a natural hybrid between M. nigrescens and M. callichroma found in the wild in Venezuela. (David Haelterman)
Christenson's Unfinished Monograph notes in Orchid Digest 64 (1):13, 2000: Maxillaria tonsbergii is often confused with Maxillaria nigrescens whose flowers are only about half the size of M. tonsbergii.