genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
fern
The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
s in the family Osmundaceae. It is recognized in the
Pteridophyte Phylogeny Group
The Pteridophyte Phylogeny Group (PPG) is an informal international group of systematic botanists who collaborate to establish on the classification of pteridophytes ( lycophytes and ferns) that reflects knowledge about plant relationships discove ...
classification of 2016 (PPG I), but kept within a more broadly circumscribed genus '' Osmunda'' by other sources. The genus is known from Early Cretaceous to present.
Taxonomy
, the ''Checklist of Ferns and Lycophytes of the World'' accepted the following four species:
Phylogeny of ''Plenasium''
The following fossil species are also accepted.
* †''P. arnoldii'' (C.N.Mill. 1967) Bomfleur, Grimm & McLoughlin 2017
* †''P. bransonii'' (Tidwell & Medlyn, 1991) Bomfleur, Grimm & McLoughlin 2017 (?Eocene: New Mexico, USA).
* †''P. burgii'' (Tidwell & J.E.Skog, 2002) Bomfleur, Grimm & McLoughlin 2017 (Early Cretaceous: Nebraska, USA).
* †''P. chandleri'' (Arnold 1952) Bomfleur, Grimm & McLoughlin
* †''P. crossii'' (Tidwell & L.R.Parker, 1987) Bomfleur, Grimm & McLoughlin 2017 (Paleocene: Wyoming, USA).
* †''P. dakotense'' (Tidwell & J.E.Skog, 2002) Bomfleur, Grimm & McLoughlin 2017 (Early Cretaceous: South Dakota, USA).
* †''P. dowkeri'' (Carruthers 1870) Bomfleur, Grimm & McLoughlin 2017
* †''P. moorei'' (Tidwell & Medlyn, 1991) Bomfleur, Grimm & McLoughlin 2017 (?Eocene: New Mexico, USA).
* †''P. nebraskense'' (Tidwell & J.E.Skog, 2002) Bomfleur, Grimm & McLoughlin 2017 (Early Cretaceous: Nebraska, USA).
*†''P.'' (''Aurealcaulis'') ''elegans'' Hiller et al. 2019 (Eocene, Vietnam)
*†''P. (Plenasium) xiei'' Cheng et al. 2019 (Late Cretaceous, Northeastern China)