Medusaegraptus mirabilis Ruedemann was originally described as a dendroid graptolite and is currently listed in the Treatise on Invertebrate Paleontology among graptolites incertae sedis. Recently, several localities yielding abundant M. mirabilis were discovered, prompting renewed interest in the taxonomic affinities of this species. Based on a study of the morphology and paleoecology of M. mirabilis, this species is herein considered to represent a noncalcified dasyclad alga. Other species of Medusaegraptus are similarly considered.
Medusaegraptid-bearing strata commonly contain other exceptionally preserved fossils and represent conservation lagerstaetten. Consideration of medusaegraptids as dasyclad algae restricts the depth at which these deposits could have occurred.