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59-823: Bennettitales (also known as cycadeoids ) is an extinct order of seed plants that first appeared in the Permian period and became extinct in most areas toward the end of the Cretaceous . Bennettitales were amongst the most common seed plants of the Mesozoic , and had morphologies including shrub and cycad -like forms. The foliage of bennettitaleans is superficially nearly indistinguishable from that of cycads, but they are distinguished from cycads by their more complex flower-like reproductive organs, at least some of which were likely pollinated by insects . Although certainly gymnosperms sensu lato (cone-bearing seed plants),

118-461: A cohors (plural cohortes ). Some of the plant families still retain the names of Linnaean "natural orders" or even the names of pre-Linnaean natural groups recognized by Linnaeus as orders in his natural classification (e.g. Palmae or Labiatae ). Such names are known as descriptive family names. In the field of zoology , the Linnaean orders were used more consistently. That is,

177-510: A divaricate branching habit, similar to that of Banksia . It has been suggested that Williamsoniaceae are a paraphyletic (not containing all descendants of a common ancestor) assemblage of all Bennettitales that do not belong to the Cycadeoidaceae. In general, bennettitalean leaves are attached to the stem with a helical (corkscrew) arrangement. Some leaves (most species of Nilssoniopteris , etc.) are narrow, solitary blades with

236-458: A megagametophyte — is also called the embryo sac in angiosperms . The megagametophyte produces an egg cell for the purpose of fertilization . The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule. On the basis of the relative position of micropyle, body of the ovule, chalaza and funicle, there are six types of ovules. In flowering plants ,

295-507: A monophyletic group when paired with Gnetales. a study in 2006 suggested that Bennettitales, Angiosperms, and Gigantopteridales form a clade based on the presence of oleanane . Molecular evidence has consistently contradicted the Anthophyte hypothesis, finding that Angiosperms are the sister group to all living gymnosperms, including Gnetales. Some authors have suggested due to similarities between their seed coats, Bennettitales form

354-426: A palmate appearance similar to early species of Ginkgo . The foliage of bennettitaleans resembles that of cycads to such an extent that the foliage of the two groups cannot be reliably distinguished based on gross morphology alone. However, fossil foliage which preserves the cuticle can be assigned to either group with confidence. The stomata of bennettitaleans are described as syndetocheilic . This means that

413-402: A taxonomist , as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with

472-509: A capital letter. For some groups of organisms, their orders may follow consistent naming schemes . Orders of plants , fungi , and algae use the suffix -ales (e.g. Dictyotales ). Orders of birds and fishes use the Latin suffix -iformes meaning 'having the form of' (e.g. Passeriformes ), but orders of mammals and invertebrates are not so consistent (e.g. Artiodactyla , Actiniaria , Primates ). For some clades covered by

531-631: A clade with the gymnosperm orders of Gnetales and Erdtmanithecales , dubbed the "BEG group". However, this proposal has been contested by other authors, who contend that these similarities are only superficial and do not indicate a close relationship. A 2017 phylogeny based on molecular signatures of fossilised cuticles found that Bennettitales were more closely related to the Ginkgo +Cycads clade than conifers, and were closely related to Nilssonia and Ptilozamites . The oldest confirmed fossils of bennettitaleans are leaves of Nilssoniopteris shanxiensis ,

590-570: A distinct rank of biological classification having its own distinctive name (and not just called a higher genus ( genus summum )) was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s. Carl Linnaeus was the first to apply it consistently to the division of all three kingdoms of nature (then minerals , plants , and animals ) in his Systema Naturae (1735, 1st. Ed.). For plants, Linnaeus' orders in

649-406: A long proboscis , and it has been suggested that they fed on nectar produced by bennettitalean reproductive structures, such as the bisexual williamsoniacean reproductive structure Williamsoniella , which had a long, narrow central receptacle which was likely otherwise inaccessible. Early Cretaceous bennettitalean pollen has been found directly associated with a proboscis bearing fly belonging to

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708-417: A mature embryo as the resources within the seed are limited. In flowering plants, one sperm nucleus fuses with the egg cell to produce a zygote, the other fuses with the two polar nuclei of the central cell to give rise to the polyploid (typically triploid) endosperm . This double fertilization is unique to flowering plants, although in some other groups the second sperm cell does fuse with another cell in

767-422: A megasporangium with integuments surrounding it. Ovules are initially composed of diploid maternal tissue, which includes a megasporocyte (a cell that will undergo meiosis to produce megaspores). Megaspores remain inside the ovule and divide by mitosis to produce the haploid female gametophyte or megagametophyte, which also remains inside the ovule. The remnants of the megasporangium tissue (the nucellus) surround

826-409: A pollen tube enters the micropyle. During germination , the seedling 's radicle emerges through the micropyle. Located opposite from the micropyle is the chalaza where the nucellus is joined to the integuments. Nutrients from the plant travel through the phloem of the vascular system to the funiculus and outer integument and from there apoplastically and symplastically through the chalaza to

885-436: A preovulate taxon, has a lobed structure fused to the lower third of the megasporangium, with the lobes extending upwards in a ring around the megasporangium. This might, through fusion between lobes and between the structure and the megasporangium, have produced an integument. The origin of the second or outer integument has been an area of active contention for some time. The cupules of some extinct taxa have been suggested as

944-428: A smooth-edged ("entire") margin. Most leaf morphotypes ( Pterophyllum , Ptilophyllum , Zamites , Otozamites , etc.) are pinnate (feather-shaped), with many small leaf segments attached to a central shaft. Others ( Anomozamites , a few species of Nilssoniopteris ) are incompletely pinnate (sawtooth-shaped) and transitional between these two end members. One unusual leaf form, Eoginkgoites , even approaches

1003-611: A species from the upper part of the Upper Shihhotse Formation in Shanxi Province , China . This strata is dated to the early Kungurian stage of the early Permian ( Cisuralian ), around 281 million years ago. Supposed Carboniferous-Permian records of Pterophyllum do not have conclusive bennettitalean affinities or have been reinterpreted as cycad foliage in the form genus Pseudoctenis . True Permian records of benettitalean leaves are rare; outside of

1062-459: Is associated with the female reproductive structure Williamsonia , though it is uncertain whether the parent plants were monoecious (male and female reproductive structures being present on the same plant) or dioecious (where each plant has only one gender of reproductive organ). Weltrichia was likely primarily wind-pollinated , with some species possibly pollinated by beetles. Several groups of Jurassic and Early Cretaceous insects possessed

1121-440: Is dense and thick, with many layers of differentiated cells. This contrasts with the thin, biseriate (two cell-layer) integument of gnetophytes. Bennettitaleans also lack another gnetophyte-like trait: a sheath of fused bracteoles enveloping the seed. Most integument cells are not unusual in size or shape. However, near the micropyle the innermost layer of integument cells become radially-oriented and elongated, partially closing in on

1180-663: Is often enclosed in paired synangia (pollen sacs). The synangia lie on the adaxial (inner) edge of pollen-bearing leaf-like structures known as microsporophylls . This contrasts with cycads, all of which lack discrete synangia and bear pollen on the abaxial (outer) surface of their microsporophylls. Many bennettitaleans are bisporangiate , where the pollen and ovules are hosted on the same (bisexual or hermaphrodite) cone. Cavities filled with curved synangia-bearing microsporophylls are encased by thin radiating structures, including thick, infertile interseminal scales and fertile sporophylls with ovules at their tips. The presence of ovules at

1239-522: The Fritillaria type of development (illustrated by Lilium in the figure) there is no separation of the megaspores following meiosis, then the nuclei fuse to form a triploid nucleus and a haploid nucleus. The subsequent arrangement of cells is similar to the Polygonum pattern, but the ploidy of the nuclei is different. After fertilization, the nucellus may develop into the perisperm that feeds

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1298-528: The International Code of Zoological Nomenclature , several additional classifications are sometimes used, although not all of these are officially recognized. In their 1997 classification of mammals , McKenna and Bell used two extra levels between superorder and order: grandorder and mirorder . Michael Novacek (1986) inserted them at the same position. Michael Benton (2005) inserted them between superorder and magnorder instead. This position

1357-486: The Isle of Portland , England, which Buckland gave the genus name Cycadeoidea . Buckland provided a description of the family and two species, but failed to give a description of the genus, which has led to Buckland's description of the family being considered invalid by modern taxonomic standards. In publications in 1870, Scottish botanist William Carruthers and English paleobotanist William Crawford Williamson described

1416-496: The Maastrichtian , assignable to Pterophyllum. A possible late record has been reported from the early Oligocene of eastern Australia and Tasmania , assignable to the genus Ptilophyllum , but no cuticle was preserved, making the referral inconclusive. Bennettitales is typically considered the sole order in the class Bennettitopsida Engler (1897) or Cycadeoideopsida Scott (1923) . Most paleobotanists prefer

1475-557: The Middle Triassic , and williamsoniaceans became globally distributed by the end of the period. The oldest bennettitalean reproductive structures are small Williamsonia "flowers" from the Middle Triassic Esk Formation of Australia . While Williamsoniaceae had a global distribution, Cycadeoidaceae appear to have been primarily confined to the western parts of Laurasia , and are primarily known from

1534-815: The Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. When the word ordo was first consistently used for natural units of plants, in 19th-century works such as the Prodromus Systematis Naturalis Regni Vegetabilis of Augustin Pyramus de Candolle and the Genera Plantarum of Bentham & Hooker, it indicated taxa that are now given

1593-715: The Cretaceous. Bennettitales were widespread and abundant during the Jurassic and Early Cretaceous, however Bennettitales severely declined during the Late Cretaceous, coincident with the rise of flowering plants , being mostly extinct by the end of the period, with the final known remains from the Northern Hemisphere being found in the polar latitude Kakanaut Formation in Chukotka , Russia, dating to

1652-794: The Shihhotse Formation they are only found in the Late Permian (likely Changhsingian )-age Umm Irna Formation in Jordan . This formation is notable for the early occurrence of other Mesozoic-style flora, including the earliest records of corystospermalean foliage ( Dicroidium ). The order Fredlindiales (containing the genus Fredlindia ) from the Late Triassic of Gondwana appears to be closely related to Bennettitales, but differs from it in some aspects of its reproductive organs. The bennettitalean fossil record reappeared in

1711-425: The developing megasporophyte, may be described as either tenuinucellate or crassinucellate. The former has either no cells or a single cell layer between the megasporophyte and the epidermal cells, while the latter has multiple cell layers between. Embryos may be described by a number of terms including Linear (embryos have axile placentation and are longer than broad), or rudimentary (embryos are basal in which

1770-453: The embryo. In some plants, the diploid tissue of the nucellus can give rise to the embryo within the seed through a mechanism of asexual reproduction called nucellar embryony . The haploid megaspore inside the nucellus gives rise to the female gametophyte , called the megagametophyte . In gymnosperms, the megagametophyte consists of around 2000 nuclei and forms archegonia , which produce egg cells for fertilization. In flowering plants,

1829-453: The extinct family Zhangsolvidae , providing evidence that this family acted as pollinators for the group. The interseminal scales of Bennettitales ovulate cones may have become fleshy at maturity, which could have potentially made then attractive to wild animals that served as seed dispersers. The Cycadeoideaceae (originally "Cycadeoideae") were named by English geologist William Buckland in 1828, from fossil trunks found in Jurassic strata on

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1888-526: The first known reproductive organs of the Bennettitales from Jurassic strata of Yorkshire and Jurassic-Cretaceous strata of the Isle of Wight and the Isle of Portland. Caruthers was the first to recognise that Bennettitales had distinct differences from cycads, and established the tribes "Williamsonieae" and "Bennettiteae", with the latter being named after the genus Bennettites named by Caruthers in

1947-446: The form of cones , which produce pollen and ovules (unfertilized seeds). The cones have a thick central receptacle surrounded by simple, helically-arranged fertile and infertile structures. Tissue at the base of the cone forms layers of scale-like or petal-like bracts to protect the radiating inner structures. Some authors refer to bennettitalean cones as "flowers", though they are not equivalent to true angiosperm flowers. Pollen

2006-476: The main paired guard cells develop from the same mother cells as the subsidiary cells which surround them. This contrasts with the haplocheilic stomata of cycads and conifers. In haplocheilic stomata, the ring of subsidiary cells are not derived from the same original structures as the guard cells. This fundamental difference is the main way to differentiate bennettitalean and cycad foliage. Like other gymnosperms, bennettitalean reproductive inflorescences come in

2065-428: The megagametophyte (also referred to as the embryo sac ) is much smaller and typically consists of only seven cells and eight nuclei. This type of megagametophyte develops from the megaspore through three rounds of mitotic divisions. The cell closest to the micropyle opening of the integuments differentiates into the egg cell, with two synergid cells by its side that are involved in the production of signals that guide

2124-418: The megagametophyte to produce a second embryo. The plant stores nutrients such as starch , proteins , and oils in the endosperm as a food source for the developing embryo and seedling, serving a similar function to the yolk of animal eggs. The endosperm is also called the albumen of the seed. the zygote then develops into a megasporophyte, which in turn produces one or more megasporangia. The ovule, with

2183-465: The megagametophyte. Megagametophytes produce archegonia (lost in some groups such as flowering plants), which produce egg cells. After fertilization, the ovule contains a diploid zygote and then, after cell division begins, an embryo of the next sporophyte generation. In flowering plants, a second sperm nucleus fuses with other nuclei in the megagametophyte forming a typically polyploid (often triploid) endosperm tissue, which serves as nourishment for

2242-409: The micropyle faces the placenta (this is the most common ovule orientation in flowering plants), amphitropous , campylotropous , or orthotropous ( anatropous are common and micropyle is in downward position and chalazal end in on the upper position hence, in amphitropous the anatropous arrangement is tilted 90 degrees and in orthotropous it is completely inverted) . The ovule appears to be

2301-449: The micropyle. The nucellus and integument are unfused above the chalaza (base of the seed), unlike cycads or gnetophytes, where the layers are fused for much of their height. Cycadeoidaceans have been suggested to have been self-pollinating, with their stems and cones buried underground, although it has alternatively been proposed that they were pollinated by beetles. The flower-like williamsoniacean male reproductive structure Weltrichia

2360-413: The nucellus completely but retain an opening at the apex referred to as the micropyle . The micropyle opening allows the pollen (a male gametophyte ) to enter the ovule for fertilization. In gymnosperms (e.g., conifers), the pollen is drawn into the ovule on a drop of fluid that exudes out of the micropyle, the so-called pollination drop mechanism. Subsequently, the micropyle closes. In angiosperms, only

2419-402: The nucellus contains a megasporocyte (megaspore mother cell), which undergoes sporogenesis via meiosis . In the megasporocyte of Arabidopsis thaliana , meiosis depends on the expression of genes that facilitate DNA repair and homologous recombination . In gymnosperms, three of the four haploid spores produced in meiosis typically degenerate, leaving one surviving megaspore inside

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2478-399: The nucellus inside the ovule. In chalazogamous plants, the pollen tubes enter the ovule through the chalaza instead of the micropyle opening. The nucellus (plural: nucelli) is part of the inner structure of the ovule, forming a layer of diploid ( sporophytic ) cells immediately inside the integuments. It is structurally and functionally equivalent to the megasporangium . In immature ovules,

2537-650: The nucellus. Among angiosperms, however, a wide range of variation exists in what happens next. The number (and position) of surviving megaspores, the total number of cell divisions, whether nuclear fusions occur, and the final number, position and ploidy of the cells or nuclei all vary. A common pattern of embryo sac development (the Polygonum type maturation pattern) includes a single functional megaspore followed by three rounds of mitosis. In some cases, however, two megaspores survive (for example, in Allium and Endymion ). In some cases all four megaspores survive, for example in

2596-708: The orders in the zoology part of the Systema Naturae refer to natural groups. Some of his ordinal names are still in use, e.g. Lepidoptera (moths and butterflies) and Diptera (flies, mosquitoes, midges, and gnats). In virology , the International Committee on Taxonomy of Viruses 's virus classification includes fifteen taxomomic ranks to be applied for viruses , viroids and satellite nucleic acids : realm , subrealm , kingdom , subkingdom, phylum , subphylum , class, subclass, order, suborder, family, subfamily , genus, subgenus , and species. There are currently fourteen viral orders, each ending in

2655-519: The origin of the outer integument. A few angiosperms produce vascular tissue in the outer integument, the orientation of which suggests that the outer surface is morphologically abaxial. This suggests that cupules of the kind produced by the Caytoniales or Glossopteridales may have evolved into the outer integument of angiosperms. The integuments develop into the seed coat when the ovule matures after fertilization. The integuments do not enclose

2714-414: The other hand, feature an exposed crown of tapering microsporophylls with adaxial rows of synangia. The microsporophylls may host a single linear row of paired synangia, or instead synangia arranged in a pinnate (feather-shaped) pattern. Seeds are dicotyledonous (possess two embryonic leaves ), with a central embryo surrounded by three layers: the thin megagametophyte, the slightly thicker nucellus , and

2773-466: The ovule is located inside the portion of the flower called the gynoecium . The ovary of the gynoecium produces one or more ovules and ultimately becomes the fruit wall. Ovules are attached to the placenta in the ovary through a stalk-like structure known as a funiculus (plural, funiculi). Different patterns of ovule attachment, or placentation , can be found among plant species, these include: In gymnosperms such as conifers, ovules are borne on

2832-460: The pollen tube. Three antipodal cells form on the opposite (chalazal) end of the ovule and later degenerate. The large central cell of the embryo sac contains two polar nuclei . The pollen tube releases two sperm nuclei into the ovule. In gymnosperms, fertilization occurs within the archegonia produced by the female gametophyte. While it is possible that several egg cells are present and fertilized, typically only one zygote will develop into

2891-564: The precursor of the currently used International Code of Nomenclature for algae, fungi, and plants . In the first international Rules of botanical nomenclature from the International Botanical Congress of 1905, the word family ( familia ) was assigned to the rank indicated by the French famille , while order ( ordo ) was reserved for a higher rank, for what in the 19th century had often been named

2950-458: The protective integument . The upper tip of the seed is tapered and opens through a thin and often extended micropyle . A long, narrow micropyle extending out of the seed is superficially similar to the condition in living gnetophytes . Once the seed is fertilized, the micropyle is sealed by a plug-shaped extension of the nucellus. Unlike living gymnosperms, the tip of the nucellus lacks a pollen chamber (receptacle for stored pollen). The integument

3009-502: The rank of family (see ordo naturalis , ' natural order '). In French botanical publications, from Michel Adanson 's Familles naturelles des plantes (1763) and until the end of the 19th century, the word famille (plural: familles ) was used as a French equivalent for this Latin ordo . This equivalence was explicitly stated in the Alphonse Pyramus de Candolle 's Lois de la nomenclature botanique (1868),

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3068-1026: The relationships of bennettitaleans to other seed plants is debated. Their general resemblance to cycads is contradicted by numerous more subtle features of their reproductive systems and leaf structure. Some authors have linked bennettitaleans to angiosperms (flowering plants) and gnetophytes (a rare and unusual group of modern gymnosperms), forming a broader group known as Anthophyta . Molecular data contradicts this, with gnetophytes found to be much more genetically similar to conifers . The exact position of Bennettitales remains uncertain. Bennettitales are divided into two families, Cycadeoidaceae and Williamsoniaceae , which have distinct growth habits . Cycadeoidaceae had stout, cycad -like trunks with bisporangiate (containing both megaspores and microspores ) strobili (cones) serving as their reproductive structures. Williamsoniaceae either had bisporangiate or monosporangiate cones, and distinctly slender and branching woody trunks. The Williamsoniaceae grew as woody shrubs with

3127-543: The same publication , the name being in honour of British botanist John Joseph Bennett . The order Bennettitales was erected by German botanist Adolf Engler in 1892, who recognised the group as separate from the Cycadales. The Anthophyte hypothesis erected by Arber and Parking in 1907 posited that angiosperms arose from Bennettitales, as suggested by the wood-like structures and rudimentary flowers . Based on morphological data, however, Bennettitales were classified as

3186-404: The suffix -virales . Ovule In seed plants , the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument , forming its outer layer, the nucellus (or remnant of the megasporangium ), and the female gametophyte (formed from a haploid megaspore ) in its center. The female gametophyte — specifically termed

3245-406: The surface of an ovuliferous (ovule-bearing) scale, usually within an ovulate cone (also called megastrobilus ). In the early extinct seed ferns , ovules were borne on the surface of leaves. In the most recent of these taxa, a cupule (a modified branch or group of branches) surrounded the ovule (e.g. Caytonia or Glossopteris ). Ovule orientation may be anatropous , such that when inverted

3304-643: The tips of sporophylls, rather than the tips of stems, is a major difference between the cones of bennettitaleans and gnetophytes. As the cone is fertilized and matures, the microsporophylls wither away and the ovules transform into seeds. Most bennettitaleans in the family Williamsoniaceae are instead monosporangiate , with separate pollen and ovule-producing (unisexual) cones on the same plant. The ovule-producing (female) cones ( Williamsonia , etc . ) are similar to mature bisporangiate cones, with interseminal scales and ovule-tipped sporophylls enclosed by bracts. Pollen-producing (male) cones ( Weltrichia , etc . ), on

3363-475: The two families as used here, though some authors, such as Anderson & Anderson (2007), classify the order via a larger number of families. Anderson & Anderson also classified the orders Fredlindiales Anderson & Anderson (2003) and Pentoxylales Pilger & Melchior (1954) within Bennettitopsida. Order (biology) What does and does not belong to each order is determined by

3422-426: The young sporophyte. An integument is a protective layer of cells surrounding the ovule. Gymnosperms typically have one integument (unitegmic) while angiosperms typically have two integuments (bitegmic). The evolutionary origin of the inner integument (which is integral to the formation of ovules from megasporangia) has been proposed to be by enclosure of a megasporangium by sterile branches (telomes). Elkinsia ,

3481-418: Was adopted by Systema Naturae 2000 and others. In botany , the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined. The superorder rank is commonly used, with the ending -anae that was initiated by Armen Takhtajan 's publications from 1966 onwards. The order as

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