Isoetopsida

Isoetopsida
Scientific classification
Kingdom:	Plantae
Division:	Lycopodiophyta
Class:	Isoetopsida; Rolle [1]
Orders
	Isoetales ; Lepidodendrales †; Selaginellales ;
Synonyms
	Glossopsida; Selaginellopsida;

Last updated September 09, 2019

The Isoetopsida is a class of Lycopodiophyta. All extant species belong to the genus Selaginella in the order Selaginellales or to the genus Isoetes in the order Isoetales. In the past, members of this group sometimes have been placed in the classes Isoetopsida, Selaginellopsida, or Lycopodiopsida. There are c. 700 species of Selaginella and 140-150 species of Isoetes, with a cosmopolitan distribution, but often scarce to rare. Both orders are heterosporous. Some botanists split Isoetes by separating two South American species into the genus Stylites.^[2]

The Division Lycopodiophyta is a tracheophyte subgroup of the Kingdom Plantae. It is one of the oldest lineages of extant (living) vascular plants and contains extinct plants like Baragwanathia that have been dated from the Silurian. Members of Lycopodiophyta were some of the dominating plant species of the Carboniferous period. These species reproduce by shedding spores and have macroscopic alternation of generations, although some are homosporous while others are heterosporous. Most members of Lycopodiophyta bear a protostele, and the sporophyte generation is dominant. They differ from all other vascular plants in having microphylls, leaves that have only a single vascular trace (vein) rather than the much more complex megaphylls found in ferns and seed plants.

Selaginella is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses.

Isoetes, commonly known as the quillworts, is a genus of plants in the family Isoetaceae. They are lycopods and the only genus in Isoetaceae. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual species often scarce to rare. Some botanists split the genus, separating two South American species into the genus Stylites, although molecular data place these species among other species of Isoetes, so Stylites does not warrant taxonomic recognition.

Some prefer the name SelaginellopsidaA.B. Frank 1877, which has priority over "Isoetopsida"; the latter was not published until 1885. However, priority does not apply above the rank of family. Recent articles favor "Isoetopsida" because "Selaginellopsida" sometimes is ambiguously used: it may denote the same membership as Isoetopsida as described herein or it may include only the order Selaginellales.

Lycopodiophyta

Lycopodiopsida

	Lycopodiales

	Drepanophycales †

Isoetopsida

Selaginellales

Lepidodendrales †

	Pleuromeia †

	Isoetales

External mold of Lepidodendron from the Upper Carboniferous of Ohio

Lepidodendron – also known as the scale trees – is an extinct genus of primitive, vascular, tree-like plants related to the isoetes (quillworts) and lycopsids. They were part of the coal forest flora. They sometimes reached heights of over 30 metres (100 ft), and the trunks were often over 1 m (3.3 ft) in diameter. They thrived during the Carboniferous Period before going extinct. Sometimes erroneously called "giant club mosses", the genus was actually more closely related to modern quillworts than to modern club mosses.

Ohio is a Midwestern state in the Great Lakes region of the United States. Of the fifty states, it is the 34th largest by area, the seventh most populous, and the tenth most densely populated. The state's capital and largest city is Columbus. Ohio is bordered by Pennsylvania to the east, Michigan to the northwest, Lake Erie to the north, Indiana to the west, Kentucky on the south, and West Virginia on the southeast.

The most famous group within the Isoetopsida is the "scale trees" (order Lepidodendrales), which include Lepidodendron . These massive trees flourished in marshlands of the Carboniferous. Quillworts are considered their closest extant relatives and share some unusual features with these fossil trees, including the development of both bark, cambium and wood, a modified shoot system acting as roots, bipolar and secondary growth, and an upright stance.^[3]^[4]

Lepidodendrales were primitive, vascular, arborescent (tree-like) plants related to the lycopsids. They thrived during the Carboniferous period, and some reached heights of over 30 meters, with trunks often more than one meter in diameter. Sometimes called "giant club mosses", they are in fact more closely related to quillworts than to club mosses.

The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago (Mya), to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō ("coal") and ferō, and was coined by geologists William Conybeare and William Phillips in 1822.

A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. The totality of fossils is known as the fossil record.

Related Research Articles

Gametophyte a stage in the life cycle of plants and algae that undergo alternation of generations. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes

A gametophyte is one of the two alternating phases in the life cycle of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis.

A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns, sometimes referred to as true ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species.

Lycopodiopsida is a class of herbaceous vascular plants known as the clubmosses and firmosses. They have dichotomously branching stems bearing simple leaves called microphylls and reproduce by means of spores borne in sporangia at the bases of the leaves. Traditionally, the group also included the spikemosses and the quillworts but because these groups have leaves with ligules and reproduce using spores of two different sizes, both are now placed into another class, Isoetopsida that also includes the extinct Lepidodendrales. These groups, together with the horsetails are often referred to informally as fern allies.

Cycads are seed plants with a long fossil history that were formerly more abundant and more diverse than they are today. They typically have a stout and woody (ligneous) trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female (dioecious). Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not closely related to either group.

Caviidae, the cavy family, is composed of rodents native to South America and includes the domestic guinea pig, wild cavies, and the largest living rodent, the capybara. They are found across South America in open areas from moist savanna to thorn forests or scrub desert. This family of rodents has fewer members than most other rodent families, with 19 species in 6 genera in 3 subfamilies.

A pteridophyte is a vascular plant that reproduces using spores. Because pteridophytes produce neither flowers nor seeds, they are also referred to as "cryptogams", meaning that their means of reproduction is hidden. The pteridophytes include the ferns, horsetails, and the lycophytes. These are not a monophyletic group because ferns and horsetails are more closely related to seed plants than to the lycophytes. Therefore, "Pteridophyta" is no longer a widely accepted taxon, although the term pteridophyte remains in common parlance, as do pteridology and pteridologist as a science and its practitioner, to indicate lycophytes and ferns as an informal grouping, such as the International Association of Pteridologists and the Pteridophyte Phylogeny Group.

Isoetales, sometimes also written Isoëtales, is an order of plants in the class Lycopodiopsida.

Sigillaria is a genus of extinct, spore-bearing, arborescent (tree-like) plants. It was a lycopodiophyte, and is related to the lycopsids, or club-mosses, but even more closely to quillworts, as was its associate Lepidodendron.

A strobilus is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but many botanists restrict the use of the term cone to the woody seed strobili of conifers. Strobili are characterized by a central axis surrounded by spirally arranged or decussate structures that may be modified leaves or modified stems.

The Fossil Grove is a group of fossils located within Victoria Park, Glasgow, Scotland. It was discovered in 1887 and contains the fossilised stumps and roots of eleven extinct Lepidodendron trees, which are sometimes described as "giant club mosses" but are more closely related to quillworts. The Fossil Grove is managed as a museum and has been a popular tourist attraction since it opened for public viewing in 1890.

<i>Selaginella apoda</i> species of plant

Selaginella apoda, commonly known as meadow spikemoss, is a perennial lycophyte native to much of the eastern United States and parts of northeastern Mexico. The life cycle is the shortest of the genus Selaginella, as well as one of the shortest among the lycophytes. Selginella apoda is found primarily in damp soils in habitats such as swamps, wet fields, open woods and along stream banks. Selaginella apoda presents the potential for case studies involving the plant's adaptability to environmental toxins. A lowland plant, it has only been recorded at elevations below 100 meters. It is closely related to Selaginella eclipes and S. ludoviciana, both of with which it has been reported to form hybrids. This group is characterized by relatively flat strobili and large megasporophylls which occur in the same plane as the lateral leaves.

This article attempts to place key plant innovations in a geological context. It concerns itself only with novel adaptations and events that had a major ecological significance, not those that are of solely anthropological interest. The timeline displays a graphical representation of the adaptations; the text attempts to explain the nature and robustness of the evidence.

Fern allies are a diverse group of seedless vascular plants that are not true ferns. Like ferns, a fern ally disperses by shedding spores to initiate an alternation of generations.

References

↑ Rolle, Friedrich (1885). "Kryptogamen". In Förster, W.; et al. (eds.). Encyklopaedie der Naturwissenschaften. 12. pp. 211–277.
↑ Jones, David L. (1987). Encyclopaedia of Ferns . Portland, Oregon: Timber Press. pp. 52–55. ISBN 0-88192-054-1.
↑ Cryptogams: Algae, Bryophyta and Pterldophyta
↑ Stewart, Wilson N.; Gar W. Rothwell (1993). Paleobotany and the Evolution of Plants (2nd ed.). Cambridge University Press. pp. 150–153. ISBN 0-521-38294-7.

External links

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[Rolle_1885-1] Rolle, Friedrich (1885). "Kryptogamen". In Förster, W.; et al. (eds.). Encyklopaedie der Naturwissenschaften. 12. pp. 211–277.

[Jones_1987-2] Jones, David L. (1987). Encyclopaedia of Ferns . Portland, Oregon: Timber Press. pp. 52–55. ISBN 0-88192-054-1.

[3] Cryptogams: Algae, Bryophyta and Pterldophyta

[Stewart_and_Rothwell-4] Stewart, Wilson N.; Gar W. Rothwell (1993). Paleobotany and the Evolution of Plants (2nd ed.). Cambridge University Press. pp. 150–153. ISBN 0-521-38294-7.