Progymnosperm

The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophytes, and eventually gave rise to the gymnosperms.[1] They have been treated formally at the rank of division Progymnospermophyta or class Progymnospermopsida (as opposite). The stratigraphically oldest known examples belong to the Middle Devonian order the Aneurophytales, with forms such as Protopteridium, in which the vegetative organs consisted of relatively loose clusters of axes.[2] Tetraxylopteris is another example of a genus lacking leaves. In more advanced aneurophytaleans such as Aneurophyton these vegetative organs started to look rather more like fronds,[3] and eventually during Late Devonian times the aneurophytaleans are presumed to have given rise to the pteridosperm order, the Lyginopteridales. In Late Devonian times, another group of progymnosperms gave rise to the first really large trees known as Archaeopteris.

Other characteristics:

Progymnosperm
Temporal range: Middle Devonian–Mississippian
Archaeopteris
Archaeopteris fossil leaves
Scientific classification
Division: Tracheophyta
Class: Progymnospermopsida
Orders

Phylogeny

Progymnosperms are a paraphyletic grade of plants.[4][5]

Tracheophyta

Rhyniopsida

Lycopodiophytina (Clubmosses, Spikemosses & Quillworts)

Eophyllophyton

Trimerophytopsida

Moniliformopses

Polypodiophytina (Ferns)

Radiatopses

Pertica

Lignophytes

†Aneurophytopsida

Metalignophytes

Archaeopteridopsida

†Protopityales Nemejc 1963

Spermatophytina (Seed plants)

Progymnosperm

Taxonomy

An updated classification of Progynopserms based on the work by Novíkov & Barabaš-Krasni 2015[6] with plant taxon authors from Anderson, Anderson & Cleal 2007[7]

  • Genus †Pertica Kasper & Andrews 1972
  • Order †Cecropsidales Stubblefield 1969
    • Family †Cecropsidaceae Stubblefield 1969
  • Order †Protopityales Nemejc 1963
    • Family †Protopityaceae Solms-Laubach 1893
  • Class †Noeggerathiopsida Krysht. 1934
    • Order †Noeggerathiales Darrah 1939
      • Family †Noeggerathiaceae Göpp. ex von Eichwald 1854
    • Order †Discinitales Doweld 2001
      • Family †Discinitaceae Gao & Thomas 1994
    • Order †Tingiales Zimmermann 1959
      • Family †Tingiaceae Koidzumi 1938 [Tingiostachyaceae Gao 1987]
  • Class †Aneurophytopsida Bierhorst ex Takhtajan 1978 [Protopteridiopsida]
    • Order †Aneurophytales Kräusel [Protopteridiales Hoeg 1942]
      • Family †Aneurophytaceae Kräusel & Weyland 1941 [Protopteridiaceae (Kräusel 1932) Kräusel & Weyland 1941]
      • Family †Protokalonaceae Barnard & Long 1975
  • Class †Archaeopteridopsida Takhtajan 1978
    • Order †Archaeopteridales Zimmermann 1930 [Siderallales Nemejc 1963; Svalbardiales Nemejc 1963]
      • Family †Archaeopteridaceae Schmalhausen 1894 [Siderallaceae Nemejc 1961; Svalbardiaceae (Zimmermann 1950) Novak 1961]

References

  1. ^ Stewart, W.N.; Rothwell, G.W. (1993). Paleobiology and the evolution of plants. Cambridge University Press. p. 521pp.
  2. ^ Lang, W. H. (1925). "Contributions to the study of the Old Red Sandstone flora of Scotland. I. On plant-remains from the fish-beds of Cromarty. II. On a sporangium-bearing branch-system from the Stromness Beds." Transactions of the Royal Society of Edinburgh, 54: 253-279.
  3. ^ Serlin, B. S. & Banks, H. P. (1978). "Morphology and anatomy of Aneurophyton, a progymnosperm from the Late Devonian of New York. Palaeontographica Americana, 8: 343-359.
  4. ^ Crane, P.R.; Herendeen, P. & Friis, E.M. (2004), "Fossils and plant phylogeny", American Journal of Botany, 91: 1683–99, doi:10.3732/ajb.91.10.1683, PMID 21652317
  5. ^ Pelletier (2012). "Empire biota: taxonomy and evolution 2nd ed". Lulu.com: 354. ISBN 1329874005.
  6. ^ Novíkov & Barabaš-Krasni (2015). "Modern plant systematics". Liga-Pres: 685. doi:10.13140/RG.2.1.4745.6164. ISBN 978-966-397-276-3.
  7. ^ Anderson, Anderson & Cleal (2007). "Brief history of the gymnosperms: classification, biodiversity, phytogeography and ecology". Strelitzia. SANBI. 20: 280. ISBN 978-1-919976-39-6.

External links

2019 in paleobotany

This article records new taxa of fossil plants that are scheduled to be described during the year 2019, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2019.

Aneurophyton

Aneurophyton is a genus of extinct vascular plants that belong to the Aneurophytales, a class of progymnosperms. The genus is primarily known from records of two well-known species found in mostly Middle Devonian and Upper Devonian (late Eifelian to Famennian) outcrops in Belgium, China (West Junggar), Germany, and the United States (New York). Some uncertain species within the genus are also recorded from Middle Devonian outcrops in Kazakhstan, Russia (Timan and Siberia), and the Ukraine. While a number of species have been described in the paleobotanical literature, the genus likely only contains two well-circumscribed species, A. germanicum and A. doui, and possibly a third species, A. olnense, from Fammenian outcrops in Belgium. If the ages of the Early Devonian (Emsian) records of A. germanicum reported from Siberia are confirmed, these would constitute the oldest records of this genus.

Archaeopteridaceae

The Archaeopteridaceae are an extinct family of plants belonging to Progymnospermae, and were dominant forest trees of the Late Devonian.

Archaeopteridales

The Archaeopteridales are an extinct order of plants belonging to Progymnospermae, and dominant forest trees of the Late Devonian.

Coal forest

Coal forests were the vast swathes of wetlands that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times. As vegetable matter from these forests decayed, enormous deposits of peat accumulated, which later changed into coal.

Much of the carbon in the peat deposits produced by coal forests came from photosynthetic splitting of existing carbon dioxide, which released the accompanying split-off oxygen into the atmosphere. This process may have greatly increased the oxygen level, possibly as high as about 35%, making the air more easily breathable by animals with inefficient respiratory systems, as indicated by the size of Meganeura compared to modern dragonflies.Coal forests covered tropical Euramerica (Europe, eastern North America, northwesternmost Africa) and Cathaysia (mainly China). Climate change devastated these tropical rainforests during the Carboniferous period. The Carboniferous Rainforest Collapse was caused by a cooler drier climate that initially fragmented, then collapsed the rainforest ecosystem. During most of the rest of Carboniferous times, the coal forests were mainly restricted to refugia in North America (such as the Appalachian and Illinois coal basins) and central Europe.

At the very end of the Carboniferous period, the coal forests underwent a resurgence, expanding mainly in eastern Asia, notably China; they never recovered fully in Euramerica. The Chinese coal forests continued to flourish well into Permian times. This resurgence of the coal forests in very late Carboniferous times seems to have coincided with a lowering of global temperatures and a return of extensive polar ice in southern Gondwana, perhaps due to lessening of the greenhouse effect as the massive coal deposition process abstracted carbon dioxide from the atmosphere.

Cyanidiaceae

Cyanidiaceae is a family of red algae, one of two families in the Division Cyanidiophytina.

Cyanidiophytina

Cyanidiophytina is a subdivision of red algae.In older texts it was described as an order "Cyanidiales". It was granted division status in the Saunders and Hommersand 2004 classification (as "Cyanidophyta"), but was only elevated to subdivision Cyanidiophytina in the Yoon et al. classification of 2006.

Devonian

The Devonian ( deh-VOH-nee-ən) is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning of the Carboniferous, 358.9 Mya. It is named after Devon, England, where rocks from this period were first studied.

The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established.

Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fishes." The first ray-finned and lobe-finned bony fish appeared, while the placoderms began dominating almost every known aquatic environment. The ancestors of all four-limbed vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral and pelvic fins gradually evolved into legs. In the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician.

The first ammonites, species of molluscs, appeared. Trilobites, the mollusc-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida.

The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small continent of Euramerica in between.

Galdieriaceae

Galdieriaceae is a family of red algae, one of two families in the order Cyanidiales.

Geologic time scale

The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history. The table of geologic time spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy (ICS).

Horneophytopsida

Horneophytopsida is a class of extinct plants which consisted of branched stems without leaves, true roots or vascular tissue, found from the Late Silurian to the Early Devonian (around 430 to 390 million years ago). They are the simplest known polysporangiophytes, i.e. plants with sporophytes bearing many spore-forming organs (sporangia) on branched stems. They were formerly classified among the rhyniophytes, but it was later found that some of the original members of the group had simple vascular tissue and others did not.In 2004, Crane et al. published a cladogram for the polysporangiophytes in which the Horneophytopsida are shown as the sister group of all other polysporangiophytes. One other former rhyniophyte, Aglaophyton, is also placed outside the tracheophyte clade, as it did not possess true vascular tissue (in particular did not have tracheids), although its conducting tissue is more complex than that of the Horneophytopsida.

Lycopodiophyta

The Division Lycopodiophyta (sometimes called lycophyta or lycopods) 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 (ca. 425 million years ago). 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.

Lycopodiopsida

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 (Selaginella and relatives) and the quillworts (Isoetes and relatives) 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.

The class Lycopodiopsida as interpreted here contains a single living order, the Lycopodiales, and a single extinct order, the Drepanophycales.

Phanerozoic

The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. Its name was derived from the Ancient Greek words φανερός (phanerós) and ζωή (zōḗ), meaning visible life, since it was once believed that life began in the Cambrian, the first period of this eon. The term "Phanerozoic" was coined in 1930 by the American geologist George Halcott Chadwick (1876–1953). The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

The time span of the Phanerozoic starts with the sudden appearance of fossilized evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.

Rhacophytales

Rhacophytales are an extinct group of plants from the Devonian period.

The representatives are characterized by a unique branching system in which bi- and quadriseriate units occur which are located in the axils of special structures, the aphlebiae. These are abnormal leaflets on the rhachis of ferns. The appendages of the last branching stage can be dichotomously branched, in some forms they stand in one plane. The vascular system consists of a clepsydroid primary xylem with a cross section and a secondary xylem. The sporangia are in groups and have no annulus. All representatives must have been homosporous.

The exact taxonomic position of Rhacophytales is still unclear. Rhacophyton was considered to be part of Aneurophytales (a progymnosperm order) in the past, when it was regarded as a precursor of seed ferns and true ferns. It was considered to be in Protopteridales, Zygopteridales, or the basal group in Coenopteridales, an polyphyletic group containing also Stauropteridales and Zygopteridales.

The representatives of the order share characteristics with some representatives of Iridopteridales and the progymnosperms. Some authors put them as a family in Zygopteridales, a fossil fern group. With them, they share glass-shaped xylem and quadriseriate branching. With the progymnosperms they share secondary xylem.

Taylor, Taylor and Krings (2009) see them as more evolved than Trimerophyta from which they originated, but they lack the organ differentiation found in the somewhat younger fern-like plants.

Streptophyta

Streptophyta, informally the streptophytes (from the Greek strepto, for twisted, i.e., the morphology of the sperm of some members), is a clade of plants. The composition of the clade varies considerably between authors, but the definition employed here includes land plants and all green algae except the Chlorophyta and possibly the more basal Mesostigmatophyceae, Chlorokybophyceae, and Spirotaenia.

Tetraxylopteris

Tetraxylopteris is a genus of extinct vascular plants of the Middle to Upper Devonian (around 390 to 360 million years ago). Fossils were first found in New York State, USA. A second species was later found in Venezuela.

Wildfire

A wildfire, wildland fire or rural fire is an uncontrolled fire in an area of combustible vegetation occurring in rural areas. Depending on the type of vegetation present, a wildfire can also be classified more specifically as a brush fire, bushfire, desert fire, forest fire, grass fire, hill fire, peat fire, vegetation fire, or veld fire. Many organizations consider wildfire to mean an unplanned and unwanted fire , while wildland fire is a broader term that includes prescribed fire as well as wildland fire use (WFU; these are also called monitored response fires).

Fossil charcoal indicates that wildfires began soon after the appearance of terrestrial plants 420 million years ago. Wildfire's occurrence throughout the history of terrestrial life invites conjecture that fire must have had pronounced evolutionary effects on most ecosystems' flora and fauna. Earth is an intrinsically flammable planet owing to its cover of carbon-rich vegetation, seasonally dry climates, atmospheric oxygen, and widespread lightning and volcanic ignitions.Wildfires can be characterized in terms of the cause of ignition, their physical properties, the combustible material present, and the effect of weather on the fire. Wildfires can cause damage to property and human life, although naturally occurring wildfires may have beneficial effects on native vegetation, animals, and ecosystems that have evolved with fire.High-severity wildfire creates complex early seral forest habitat (also called "snag forest habitat"), which often has higher species richness and diversity than unburned old forest. Many plant species depend on the effects of fire for growth and reproduction. Wildfires in ecosystems where wildfire is uncommon or where non-native vegetation has encroached may have strongly negative ecological effects.Wildfire behavior and severity result from a combination of factors such as available fuels, physical setting, and weather. Analyses of historical meteorological data and national fire records in western North America show the primacy of climate in driving large regional fires via wet periods that create substantial fuels, or drought and warming that extend conducive fire weather.Strategies for wildfire prevention, detection, and suppression have varied over the years. One common and inexpensive technique is controlled burning: intentionally igniting smaller fires to minimize the amount of flammable material available for a potential wildfire. Vegetation may be burned periodically to maintain high species diversity and limit the accumulation of plants and other debris that may serve as fuel. Wildland fire use is the cheapest and most ecologically appropriate policy for many forests. Fuels may also be removed by logging, but such thinning treatments may not be effective at reducing fire severity under extreme weather conditions. Wildfire itself is reportedly "the most effective treatment for reducing a fire's rate of spread, fireline intensity, flame length, and heat per unit of area", according to Jan Van Wagtendonk, a biologist at the Yellowstone Field Station. Building codes in fire-prone areas typically require that structures be built of flame-resistant materials and a defensible space be maintained by clearing flammable materials within a prescribed distance from the structure.

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