24-599: See text Erdtmanithecales is an extinct order of gymnosperm plants known from the Mesozoic era . Known remains include pollen organs and seeds associated with Eucommiidites pollen, which is considered diagnostic for the order. The order was first described in 1996. While Eucommiidites pollen first appears in the Early Jurassic, associated floral remains are not found until the Early Cretaceous. It
48-462: A group of vascular plants that include the clubmosses . They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina . They are one of the oldest lineages of extant (living) vascular plants; the group contains extinct plants that have been dated from the Silurian (ca. 425 million years ago). Lycophytes were some of the dominating plant species of
72-408: A now-extinct family with members which (in an example of convergent evolution ) resembled the modern butterflies that arose far later. All gymnosperms are perennial woody plants , Unlike in other extant gymnosperms the soft and highly parenchymatous wood in cycads is poorly lignified, and their main structural support comes from an armor of sclerenchymatous leaf bases covering the stem, with
96-439: A single vascular trace (vein), rather than the much more complex megaphylls of other vascular plants. The extinct genus Asteroxylon represents a transition between these two groups: it has a vascular trace leaving the central protostele, but this extends only to the base of the enation. See § Evolution of microphylls . Zosterophylls and extant lycophytes are all relatively small plants, but some extinct species, such as
120-399: Is thought that the group are closely related to Gnetales as well as possibly Bennettitales . Gymnosperm The gymnosperms ( / ˈ dʒ ɪ m n ə ˌ s p ɜːr m z , - n oʊ -/ JIM -nə-spurmz, -noh- ; lit. ' revealed seeds ' ) are a group of seed-producing plants that include conifers , cycads , Ginkgo , and gnetophytes , forming
144-467: The Carboniferous period, and included the tree-like Lepidodendrales , some of which grew over 40 metres (130 ft) in height, although extant lycophytes are relatively small plants. The scientific names and the informal English names used for this group of plants are ambiguous. For example, "Lycopodiophyta" and the shorter "Lycophyta" as well as the informal "lycophyte" may be used to include
168-463: The Lepidodendrales , were tree-like, and formed extensive forests that dominated the landscape and contributed to the formation of coal . In the broadest circumscription of the lycophytes, the group includes the extinct zosterophylls as well as the extant (living) lycophytes and their closest extinct relatives. The names and ranks used for this group vary considerably. Some sources use
192-555: The Zosterophyllopsida by the possession of microphylls . Some zosterophylls, such as the Devonian Zosterophyllum myretonianum , had smooth stems (axes). Others, such as Sawdonia ornata , had flap-like extensions on the stems ("enations"), but without any vascular tissue. Asteroxylon , identified as an early lycopodiopsid, had vascular traces that extended to the base of the enations. Species in
216-482: The euphyllophytes , such as ferns , gymnosperms and flowering plants . They are defined by two synapomorphies : lateral rather than terminal sporangia (often kidney-shaped or reniform), and exarch protosteles , in which the protoxylem is outside the metaxylem rather than vice versa. The extinct zosterophylls have at most only flap-like extensions of the stem ("enations") rather than leaves, whereas extant lycophyte species have microphylls , leaves that have only
240-419: The "zosterophylls" comprise a paraphyletic group, ranging from forms like Hicklingia , which had bare stems, to forms like Sawdonia and Nothia , whose stems are covered with unvascularized spines or enations. The genus Renalia illustrates the problems in classifying early land plants. It has characteristics both of the non-lycophyte rhyniophytes – terminal rather than lateral sporangia – and of
264-571: The clade Gymnospermae . The term gymnosperm comes from the composite word in Greek : γυμνόσπερμος ( γυμνός , gymnos , 'naked' and σπέρμα , sperma , 'seed'), and literally means 'naked seeds'. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants ( angiosperms ), which are enclosed within an ovary . Gymnosperm seeds develop either on
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#1732780196775288-914: The exception of species with underground stems. There are no herbaceous gymnosperms and compared to angiosperms they occupy fewer ecological niches , but have evolved both parasites ( Parasitaxus ), epiphytes ( Zamia pseudoparasitica ) and rheophytes ( Retrophyllum minus ). Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65–70 genera and 600–630 species (696 accepted names). Most conifers are evergreens . The leaves of many conifers are long, thin and needle-like, while other species, including most Cupressaceae and some Podocarpaceae , have flat, triangular scale-like leaves. Agathis in Araucariaceae and Nageia in Podocarpaceae have broad, flat strap-shaped leaves. Cycads are
312-525: The extant lycophytes and their closest extinct relatives. The consensus classification produced by the Pteridophyte Phylogeny Group classification in 2016 (PPG I) places all extant (living) lycophytes in the class Lycopodiopsida . There are around 1,290 to 1,340 such species. For more information on the classification of extant lycophytes, see Lycopodiopsida § Classification . A major cladistic study of land plants
336-402: The extinct zosterophylls or to exclude them. Lycophytes reproduce by spores and have alternation of generations in which (like other vascular plants) the sporophyte generation is dominant. Some lycophytes are homosporous while others are heterosporous . When broadly circumscribed , the lycophytes represent a line of evolution distinct from that leading to all other vascular plants ,
360-824: The gnetophytes among the conifers. Numerous extinct seed plant groups are recognised including those considered pteridosperms/seed ferns , as well other groups like the Bennettitales. By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes ( Gnetum , Ephedra and Welwitschia ), and Ginkgo biloba (a single living species). About 65% of gymnosperms are dioecious , but conifers are almost all monoecious . Some genera have mycorrhiza , fungal associations with roots ( Pinus ), while in some others ( Cycas ) small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria . Over 1,000 living species of gymnosperm exist. It
384-550: The late Devonian period around 383 million years ago. It has been suggested that during the mid-Mesozoic era, pollination of some extinct groups of gymnosperms was by extinct species of scorpionflies that had specialized proboscis for feeding on pollination drops. The scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has also been found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings ,
408-476: The modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used. The gymnosperms and angiosperms together constitute the spermatophytes or seed plants. The spermatophytes are subdivided into five divisions , the angiosperms and four divisions of gymnosperms: the Cycadophyta , Ginkgophyta , Gnetophyta , and Pinophyta (also known as Coniferophyta). Newer classification place
432-421: The names "Lycopodiophyta" or the shorter "Lycophyta" to include zosterophylls as well as extant lycophytes and their closest extinct relatives, while others use these names to exclude zosterophylls. The name "Lycopodiophytina" has also been used in the inclusive sense. English names, such as "lycophyte", "lycopodiophyte" or "lycopod", are similarly ambiguous, and may refer to the broadly defined group or only to
456-1098: The next most abundant group of gymnosperms, with two or three families, 11 genera, and approximately 338 species. A majority of cycads are native to tropical climates and are most abundantly found in regions near the equator. The other extant groups are the 95–100 species of Gnetales and one species of Ginkgo . Today, gymnosperms are the most threatened of all plant groups. Ginkgo Cycas Dioon Bowenia Macrozamia Encephalartos Lepidozamia Ceratozamia Stangeria Microcycas Zamia Ephedra Gnetum Welwitschia Larix Pseudotsuga Pinus Cathaya Picea Cedrus Abies Keteleeria Pseudolarix Nothotsuga Tsuga Araucaria Agathis Wollemia Halocarpus Pectinopitys Prumnopitys Sundacarpus Lepidothamnus Phyllocladus Parasitaxus Lagarostrobos Manoao Saxegothaea Microcachrys Pherosphaera Lycopodiophyta The lycophytes , when broadly circumscribed , are
480-455: The same group as the extant orders. Different sources use varying numbers and names of the extinct orders. The following phylogram shows a likely relationship between some of the proposed Lycopodiopsida orders. Lycopodiales † Drepanophycales Selaginellales † Lepidodendrales † Pleuromeiales Isoetales Within the broadly defined lycophyte group, species placed in the class Lycopodiopsida are distinguished from species placed in
504-493: The surface of scales or leaves , which are often modified to form cones , or on their own as in yew , Torreya , and Ginkgo . The life cycle of a gymnosperm involves alternation of generations , with a dominant diploid sporophyte phase, and a reduced haploid gametophyte phase, which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to (the paraphyletic group of) all non-angiosperm seed plants. In that case, to specify
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#1732780196775528-608: The zosterophylls – kidney-shaped sporangia opening along the distal margin. A rather different view is presented in a 2013 analysis by Hao and Xue. Their preferred cladogram shows the zosterophylls and associated genera basal to both the lycopodiopsids and the euphyllophytes, so that there is no clade corresponding to the broadly defined group of lycophytes used by other authors. basal groups Adoketophyton Zosterophyllopsida Lycopsida basal groups Yunia , Dibracophyton euphyllophytes Some extinct orders of lycophytes fall into
552-679: Was previously widely accepted that the gymnosperms originated in the Late Carboniferous period, replacing the lycopsid rainforests of the tropical region, but more recent phylogenetic evidence indicates that they diverged from the ancestors of angiosperms during the Early Carboniferous . The radiation of gymnosperms during the late Carboniferous appears to have resulted from a whole genome duplication event around 319 million years ago . Early characteristics of seed plants are evident in fossil progymnosperms of
576-1009: Was published in 1997 by Kenrick and Crane. In 2004, Crane et al. published some simplified cladograms , based on a number of figures in Kenrick and Crane (1997). Their cladogram for the lycophytes is reproduced below (with some branches collapsed into 'basal groups' to reduce the size of the diagram). Cooksonia cambrensis, Renalia , Sartilmania , Uskiella , Yunia † Hicklingia Adoketophyton , Discalis , Distichophytum (= Rebuchia ), Gumuia , Huia , Zosterophyllum myretonianum , Z. llanoveranum, Z. fertile Zosterophyllum divaricatum , Tarella , Oricilla , Gosslingia , Hsua , Thrinkophyton , Protobarinophyton , Barinophyton obscurum , B. citrulliforme , Sawdonia , Deheubarthia , Konioria , Anisophyton , Serrulacaulis , Crenaticaulis Nothia , Zosterophyllum deciduum extant and extinct members In this view,
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