The species was first described as
Trichomanes caudatum by
William Brackenridge in 1854, based on material collected in
Tahiti by the
United States Exploring Expedition.
Filmy ferns (family Hymenophyllaceae) were historically divided into two genera,
Trichomanes and
Hymenophyllum by most pteridologists, based largely on the morphology of their
indusia. After reviewing the Old World species of filmy ferns,
Edwin Copeland came to believe that this arrangement was arbitrary, with a continuum of variation between indusial shapes, and lumped together disparate elements in each genus. Accordingly, he published a revised treatment of the family in 1938, splitting it into no less than thirty-three genera. One of these was the former
Trichomanes subgenus
Macroglena; he assigned
T. caudatum there as
Macroglena caudata. While Copeland's system was adopted by some botanists, others considered his genera to be unduly narrow. The advent of molecular techniques allowed Atsushi Ebihara and coworkers to redefine filmy fern genera based on
molecular phylogeny. Their classification retained the traditional
Hymenophyllum while dividing
Trichomanes sensu lato into nine genera. They adopted a narrower classification of
Cephalomanes, placing
T. caudatum in
Abrodictyum subg.
Abrodictyum as
A. caudatum. Subsequent authors have typically either used this name for the species or, reverting to the bigeneric system,
T. caudatum. In 1861,
Roelof van den Bosch described the species
Trichomanes milnei based on a collection from
Balade, New Caledonia. It has subsequently been treated as a synonym of
A. caudatum, although
Mary Tindale felt that it probably warranted recognition as a distinct species. == References ==