Ophioglossidae

See Pteridophyta for an introduction to seedless vascular plants

Ophioglossidae is the name of a plant taxon belonging to the taxonomic category Subdivision, which in the modern classification by Christenhusz et al. 2011 corresponds to the class Psilotopsida of Smith et al. 2006, which is therefore a synonym of this taxon, and comprises two orders: Psilotales and Ophioglossales as well as the families Ophioglossaceae and Psilotaceae. This group is monophyletic. Due to their characteristic simplified morphology, which hides the characters of the group, these families had not been proposed as sisters before, but molecular DNA analyzes were resounding in this regard. Some morphological characters that allow us to appreciate its monophyly are the axial and in principle underground gametophytes, and its roots without root hairs or absent, associated with fungi (mycorrhizal), among other characters. They are sisters to the Polypodiidae, Marattiidae and Equisetidae, together with all of them they form the division Monilophyta sensu Smith et al. (2006).

It is a small group with about 80 species.

Phylogeny

Theoretical Introduction in Philogenia

As circumscribed according to Christenhusz et al. 2011 (based on Smith et al. 2006, 2008); it is monophyletic. Until not many years ago Psilotum was considered a "living fossil", a true living exponent of the first vascular plants such as Rhynia. Based on several studies published since 1995 by various research groups, and later agreed upon thanks to the robust molecular analysis of DNA carried out by Pryer et al. 2001, it is recognized that the first phylogenetic line that differs from the rest of the monilophytes is the one that unites Psilotaceae with Ophioglossaceae, a relationship that was kept in the dark for a long time due to the extreme simplification present in the sporophyte of the two families.

Ophioglossidae is therefore the oldest subclass of the Monilophytes, sister to all the rest.

Location of Psilotopsida in the phylogenetic tree of tracheofitas. The clay, brother of the rest of the monilofites, brings together two monofiltic groups of brothers, Ophioglossales and Psilotales.

An alternative hypothesis (Bierhost 1977) considered Psilotaceae to be reduced leptosporangiate ferns, a hypothesis based primarily on their subterranean fungus-associated ("mycorrhizal") gametophyte, perhaps related to Gleicheniales. Today it is demonstrated by molecular studies that this hypothesis is incorrect.

Taxonomy

Theoretical Introduction in Taxonomy

The most up-to-date classification is that of Christenhusz et al. 2011 (based on Smith et al. 2006, 2008); which also provides a linear sequence of the lycophytes and monilophytes.

• Subclass: III Ophioglossidae Klinge, Fl. Est.-Liv-Churland 1: 94 (1882). Synonyms: Psilotidae Reveal, Phytology 79: 70 (1996).
  • Order E. Ophioglossales Link, Hort. Berol. 2: 151 (1833). 1 family.
    • Family 5. Ophioglossaceae Martinov, Tekhno-Bot. Slovar: 438 (1820). Synonyms: Botrychiaceae Horan., Char. You are. Fam. 15 (1847). Helminthostachyaceae Ching, Bull. Fan Mem. Inst. Biol. Bot. 10: 235 (1941). 5 genders: Cheiroglossa, Botrychium, Helminthostachys, Mankyua, Ophioglossum). References: Hauk et al. (2003), Kato (1988), Sun et al. (2001), Wagner & Wagner (1983).
  • Order F. Psilotales Prantl, Lehrb. Bot., ed. 5: 183 (1884). 1 family.
    • Family 6. Psilotaceae J.W.Griff. & Henfr., Microgr. Dict.: 540 (1855). Synonyms: Tmesipteridaceae Nakai, Chosakuronbun Mokuroku [Ord. Fam. Trib. Nov.]: 206 (1943). 2 genders: Psilotum, Tmesipteris). References: Bierhorst (1977), Brownsey & Lovis (1987), Gensel (1977).

Classification sensu Smith et al. 2006

Clades and higher taxa: Plantae (clade), Viridiplantae, Streptophyta, Streptophytina, Embryophyta, Tracheophyta, Euphyllophyta, Monilophyta, Class Psilotopsida.

Circumscription: 2 monotypic orders:

• Psilotal order, psilots.

Psilotaceae (family Psilotaceae).

• Ophioglossal order.

Ofioglosaceae (family Ophioglossaceae).

Other classifications

In other phylogenetic classifications from when molecular studies had not been done, due to the evident simplification of the sporophyte (reduced leaves, absence of roots) and the dichotomous branching plan of the stem, psilotaceae were traditionally considered related primitive tracheophytes with Rhynia, they were separated from the rest of the ferns and given their own class, as for example in Engler's classification system. Its relationship with the Ophioglossaceae, which have conspicuous megaphylls, was long obscured despite sharing characters from the gametophyte (which was traditionally considered more conserved than the sporophyte), and the characteristic symbiosis with fungi.

Ophioglossaceae, on the other hand, in traditional classifications such as Engler's, are considered within the group that brings together ferns with megaphylls, as a primitive group within them, because they are eusporangiate, have a mycorrhizal subterranean gametophyte, and prefoliate not circumcised Today it is known that the group of ferns with megaphylls is monophyletic if the Psilotales are added, it is known by the name Pterophyta, Pteropsida or Filicopsida sensu Engler.

In summary, the sensu Engler classification is as follows:

• Plantae Kingdom (poliphytic)
  • division Embryophyta asphonogama (paraphytic)
    • Pteridophyta subdivision (paraphytic)
      • class Psilotopsida sensu Engler, order Psilotales, family Psilotaceae (monophylaxis, equivalent to Psilotaceae sensu Smith et al.).
      • Filicopside class (paraphylically, would be monophyllic if Psilotopsides were added)
        • subclass Ophioglossidae, order Ophioglossales, family Ophioglossaceae (monophyletic, equivalent to Ophioglossaceae) sensu Smith et al.).

Characters

The morphological characters that allow us to visualize its belonging to the clade in Ophioglossaceae and Psilotaceae are: Ophioglossaceae has simple roots, without ramification, without root hairs, while Psilotaceae does not directly have roots; In addition, both groups have axial and in principle underground gametophytes, sporangia located on the adaxial face, and sporangium development of the eusporangiate type (large, with walls 2 cells thick, with more than 1000 spores per sporangium), among other characters.