Medullosales

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Medullosales
Temporal range: Carboniferous - Early Permian
FossilFernLeavesPennsylvanianOhio.jpg
Neuropteris ovata Hoffmann, Late Carboniferous of northeastern Ohio.
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Division:† Pteridospermatophyta
Order:† Medullosales
Corsin, 1960
Families
Synonyms
  • Neuropteridales Schimper, 1869
  • Trigonocarpales Seward, 1917
  • Codonospermales Doweld, 2001
  • Pachytestales Doweld, 2001
  • Hexapterospermales Doweld, 2001

The Medullosales is an extinct order of pteridospermous seed plants characterised by large ovules with circular cross-section and a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele, and frond-like leaves. [1] Their nearest still-living relatives are the cycads. [2]

Contents

Most medullosales were small to medium-sized trees. The largest specimens were probably of genus Alethopteris , whose fronds could be 7 metres long [3] and the trees were perhaps up to 10 metres tall. Especially in Moscovian times, many medullosales were rather smaller, with fronds only about 2 metres long, and apparently growing in dense, mutually supporting stands. [4] During Kasimovian and Gzhelian times there were also non-arboreal forms with smaller fronds (e.g. Odontopteris) that were probably scrambling or possibly climbing plants. [5]

Ovules

Cast of Trigonocarpus trilocularis ovule showing stalk attachment; Massillon Sandstone (Upper Carboniferous), NE Ohio. Trigonocarpus trilocularis Hildreth 1838.JPG
Cast of Trigonocarpus trilocularis ovule showing stalk attachment; Massillon Sandstone (Upper Carboniferous), NE Ohio.
Cast of a Trigonocarpus ovule showing one of the three longitudinal ribs. Trigonocarpus.jpg
Cast of a Trigonocarpus ovule showing one of the three longitudinal ribs.

Ovules in different medullosalean species could vary from maybe 1 cm to over 10 cm long - the latter being the largest known ovules produced by any non-angiosperm seed-plant. [6] It was traditionally believed that the ovules were borne directly on the fronds, replacing one of the pinnules on the ultimate pinnae. However, there is a strong possibility that this reconstruction was based on the chance finds of ovules having been preserved just lying on a piece of pinna rather than in organic attachment to it. A number of cases are now coming to light that suggest that the seeds were borne in clusters on relatively slender, branching axes, [7] [8] and that these trusses of ovules would have been produced from the top of the trunk among the crown of fronds.

The seed megaspore was surrounded by two layers of tissue: a vascularised nucellus and a usually three-layered integument; the nucellus and integument were completely free except at the base of the ovule. [9] There has been some debate as to the exact homologies of these tissues, and it has been argued that the vascularised nucellus was in fact the nucellus and integument that have become fused together, and that the 'integument' was homologous to a cupule that contained only one ovule. [10]

Most medullosalean ovules preserved as casts or adpressions show three longitudinal ribs and are assigned to the fossil genus Trigonocarpus. When such ovules are preserved as petrifactions, they are assigned to the fossil genera Pachytesta or Stephanospermum, depending mainly on differences in the apical form of the ovule. Another group of medullosalean seeds, usually associated with parispermacean fronds (see later), have six longitudinal ribs and are referred to as Hexagonocarpus when found as adpressions or casts, and Hexapterospermum when found as petrifactions.

Pollen organs

The pollen producing organs consisted of clusters of elongate sacs formed into a variety of cup-, bell- and cigar-shaped configurations, assigned to various fossil genera including Dolerotheca, Whittleseya, Aulacotheca and Potoniea. [11] Unlike with the ovules, there is good anatomical evidence that they were borne on the fronds, attached to the rachis. [12]

The pollen that they produce is strictly known as pre-pollen, as it germinated proximally and was thus intermediate in structure between pteridophytic spores and gymnospermous true-pollen. [13] The pollen organs of the parispermacean species (fossil genus Potoniea) produced spherical pre-pollen with a trilete mark. Most other medullosaleans produced large ovoid pre-pollen with a monolete mark, and assigned to the genus Schopfipollenites.

Stems

Most medullosaleans had unbranched, upright stems that produced a crown of fronds at the top. The most widespread are referred to the fossil genus Medullosa when found as petrifactions with anatomy preserved. When viewed in transverse section they appear to have several vascular segments passing along the length of the stem, superficially resembling the polysteles seen in tree ferns. However, detailed study of these vascular strands has shown that they merge and split along the length of the stem and in fact represents a single dissected stele. [14] As the stems increased in size, the vascular segments also expanded by adding secondary wood. [15] The vascular segments of the stele are embedded in ground tissue that contain canals or ducts thought to have contained a resin-like substance. The cortex surrounding the stele also had resin-ducts, and towards the outside of the stem there were radially aligned bands of sclerotic tissue.

Numerous species used to be recognised for what appeared to be anatomically different Medullosa stems, but many of these differences have been shown to represent changes that took place with the growth of the stem. [15] Moreover, it has been shown that very similar types of stem could bear a variety of different types of frond. [16] [17] There is a distinctive type of stem found in Late Pennsylvanian preserved floras, however, that is referred to as Medullosa endocentrica and has consistently slender stems and (uniquely for medullosaleans) axillary branching, and has been interpreted as a climbing plant. [5] Another distinctive type of stem in which the vascular segments are of two different sizes in transverse section (fossil genus Sutcliffia) has been linked with the parispermacean fronds. [18]

Foliage

Fragments of the fronds are the most frequently found fossils of the Medullosales, and they have been widely used for biostratigraphy [19] and biogeographical studies. [20] Most are characterised by a major fork of the main rachis in the lower (proximal) part of the frond. Each branch produced by the fork has an essentially pinnate appearance, superficially resembling the fronds of many ferns, but it is now thought that they in fact consist of a series of more or less overtopped dichotomies. [21] Only one group of fronds, known as parispermacean fronds (fossil genera Paripteris and Linopteris), lacked this major dichotomy although they were still thought to have been constructed from a series of overtopped dichotomies. [22]

Families

The characters used to differentiate the fossil genera have used in descending order of significance to group families based mainly on vegetative characters, notably the architecture of the frond:[ citation needed ] (1) the overall architecture of the frond, (2) the epidermis and cuticles, (3) how the pinnules are attached to the rachis, and (4) the veining pattern of the pinnules.

Compression of a Lonchopteris rugosa pinna with mesh veins, probably middle Westphalian age. Collection of the Universiteit Utrecht. Lonchopteris rugosa.jpg
Compression of a Lonchopteris rugosa pinna with mesh veins, probably middle Westphalian age. Collection of the Universiteit Utrecht.
Compression of a Neuropteris ovata, probably Kasimovian age, Spain. Pecopteris arborescens ESV.jpg
Compression of a Neuropteris ovata , probably Kasimovian age, Spain.

Alethopteridaceae

Cyclopteridaceae

Neurodontopteridaceae

Parispermaceae

Also commonly known as Potonieaceae, [1] and less commonly Rachivestitaceae or Hexapterospermaceae. [23]

incertae sedis

"Trigonocarpalean" ovules are generally attributed to medullosans. Examples are listed below. [24] [25] Codonospermum, Colpospermum, Polylophospermum, and Stephanospermum are so anatomically distinctive that some authors classify them each within a monotypic family (Codonospermaceae, Colpospermaceae, [23] Polylophospermaceae, and Stephanospermaceae, respectively). [23] [1]

Distribution

The oldest evidence of the Medullosales is of late Mississippian age. [22] [26] [27] The group became particularly diverse and abundant during Moscovian and Kasimovian times [20] when it dominated many habitats in the tropical wetland of Euramerica, especially on clastic substrates. [28] The group became extinct in Euramerica in earliest Permian (Autunian) times. They survived in China for a little longer, with evidence having been found there in the Asselian Stage. [29] There is little evidence to suggest that the Medullosales ranged into the southern latitudes of Gondwana. In the northern hemisphere, there are good late Mississippian records in temperate latitudes of Kazakhstan [30] but evidence from the higher northern latitudes in Siberia (Angara) is more equivocal.

Related Research Articles

<span class="mw-page-title-main">Gymnosperm</span> Clade of non-flowering, naked-seeded vascular plants

The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. 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 the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, 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 all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

<span class="mw-page-title-main">Paleobotany</span> Study of organic evolution of plants based on fossils

Paleobotany, also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeography), and the evolutionary history of plants, with a bearing upon the evolution of life in general. A synonym is paleophytology. It is a component of paleontology and paleobiology. The prefix palaeo- or paleo- means "ancient, old", and is derived from the Greek adjective παλαιός, palaios. Paleobotany includes the study of terrestrial plant fossils, as well as the study of prehistoric marine photoautotrophs, such as photosynthetic algae, seaweeds or kelp. A closely related field is palynology, which is the study of fossilized and extant spores and pollen.

<span class="mw-page-title-main">Ovule</span> Female plant reproductive structure

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, and the female gametophyte in its center. The female gametophyte — specifically termed 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.

<i>Glossopteris</i> Genus of extinct seed ferns

Glossopteris is the largest and best-known genus of the extinct Permian order of seed plants known as Glossopteridales. The name Glossopteris refers only to leaves, within the framework of form genera used in paleobotany.

<span class="mw-page-title-main">Pteridospermatophyta</span> Several distinct polyphyletic groups of extinct seed-bearing plants

Pteridospermatophyta, also called "pteridosperms" or "seed ferns" are a polyphyletic grouping of extinct seed-producing plants. The earliest fossil evidence for plants of this type are the lyginopterids of late Devonian age. They flourished particularly during the Carboniferous and Permian periods. Pteridosperms declined during the Mesozoic Era and had mostly disappeared by the end of the Cretaceous Period, though Komlopteris seem to have survived into Eocene times, based on fossil finds in Tasmania.

<span class="mw-page-title-main">Bennettitales</span> Extinct order of seed plants

Bennettitales 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.

<span class="mw-page-title-main">Coal forest</span> Land type during the late Carboniferous and Permian

Coal forests were the vast swathes of swamps and riparian forests that covered much of the land on Earth's tropical regions during the late Carboniferous (Pennsylvanian) and Permian periods. As plant matter from these forests decayed, enormous deposits of peat accumulated, which later became buried and converted into coal over the subsequent eras.

<i>Psaronius</i> Genus of ferns

Psaronius is an extinct genus marattialean tree fern which grew to 10m in height, and is associated with leaves of the organ genus Pecopteris and other extinct tree ferns. Originally, Psaronius was a name for the petrified stems, but today the genus is used for the entire tree fern. Psaronius tree fern fossils are found from the Carboniferous through the Permian.

<span class="mw-page-title-main">Caytoniales</span> Extinct order of plants

The Caytoniales are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around 252 to 66 million years ago. They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, some authorities consider them likely ancestors or close relatives of angiosperms. The origin of angiosperms remains unclear, and they cannot be linked with any known seed plants groups with certainty.

<span class="mw-page-title-main">Lyginopteridales</span> Prehistoric plant order

The Lyginopteridales are an extinct group of seed plants known from the Paleozoic. They were the first plant fossils to be described as pteridosperms and, thus, the group on which the concept of pteridosperms was first developed; they are the stratigraphically oldest-known pteridosperms, occurring first in late Devonian strata; and they have the most primitive features, most notably in the structure of their ovules. They probably evolved from a group of Late Devonian progymnosperms known as the Aneurophytales, which had large, compound frond-like leaves. The Lyginopteridales became the most abundant group of pteridosperms during Mississippian times, and included both trees and smaller plants. During early and most of middle Pennsylvanian times the Medullosales took over as the more important of the larger pteridosperms but the Lyginopteridales continued to flourish as climbing (lianescent) and scrambling plants. However, later in Middle Pennsylvanian times the Lyginopteridales went into serious decline, probably being out-competed by the Callistophytales that occupied similar ecological niches but had more sophisticated reproductive strategies. A few species continued into Late Pennsylvanian times, and in Cathaysia and east equatorial Gondwana they persisted into the Late Permian, but subsequently became extinct. Most evidence of the Lyginopteridales suggests that they grew in tropical latitudes of the time, in North America, Europe and China.

<span class="mw-page-title-main">Callistophytales</span> Extinct order of plants

Callistophytales is an extinct order of spermatophytes which lived from the Pennsylvanian to Permian periods. They were mainly scrambling and lianescent (vine-like) plants found in the wetland "coal swamps" of Euramerica and Cathaysia. Like many other early spermatophytes, they could be described as "seed ferns", combining ovule-based reproduction with pinnate leaves superficially similar to modern ferns.

<span class="mw-page-title-main">Callistophytaceae</span> Extinct family of seed ferns

The Callistophytaceae was a family of seed ferns (pteridosperms) from the Carboniferous and Permian periods. They first appeared in late Middle Pennsylvanian (Moscovian) times, 306.5–311.7 million years ago (Ma) in the tropical coal forests of Euramerica, and became an important component of Late Pennsylvanian vegetation of clastic soils and some peat soils. The best known callistophyte was documented from Late Pennsylvanian coal ball petrifactions in North America.

Emplectopteridaceae is an extinct family of pteridosperms known mainly from Permian floras of the Cathaysian Realm. They were mostly shrubby plants with a scrambling or upright habit, and favoured a range of habitats from arid to moist or even aquatic.

<i>Macroneuropteris</i> Extinct genus of plants

Macroneuropteris is a genus of Carboniferous seed plants in the order Medullosales. The genus is best known for the species Macroneuropteris scheuchzeri, a medium-size tree that was common throughout the late Carboniferous Euramerica. Three similar species, M. macrophylla, M. britannica and M. subauriculata are also included in the genus.

This article contains papers in paleobotany that were published in 2016.

<span class="mw-page-title-main">Calamopityaceae</span> Extinct family of flowing plants

Calamopityaceae is the largest family of the division of extinct seed-bearing plants (spermatophytes) known as Pteridospermatophyta. It is the only family in the monotypic order Calamopityales. This family is characterized by its petioles and specific wood pattern, and it grew only in the Paleozoic era, specifically in North America and Europe. Three form genera within the family are diagnosed by their stem structure: Calamopitys, Stenomyelon, and Diichinia. It was named by Solms-Laubach in 1896. Since then, its genera have been added to and grouped differently.

<span class="mw-page-title-main">Corystospermaceae</span> Extinct family of seed ferns

Corystosperms are a group of extinct seed plants belonging to the family Corystospermaceae assigned to the order Corystospermales or Umkomasiales. They were first described based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. Corystosperms are typified by a group of plants that bore forked Dicroidium leaves, Umkomasia cupulate ovulate structures and Pteruchus pollen organs, which grew as trees that were widespread over Gondwana during the Middle and Late Triassic. Other fossil Mesozoic seed plants with similar leaf and/or reproductive structures have also sometimes been included within the "corystosperm" concept sensu lato, such as the "doyleoids" from the Early Cretaceous of North America and Asia. A potential corystosperm sensu lato, the leaf genus Komlopteris, is known from the Eocene of Tasmania, around 53-50 million years old, over 10 million years after the Cretaceous–Paleogene extinction event.

This article records new taxa of fossil plants that are scheduled to be described during the year 2021, as well as other significant discoveries and events related to paleobotany that are scheduled to occur in the year 2021.

This paleobotany list records new fossil plant taxa that were to be described during the year 2023, as well as notes other significant paleobotany discoveries and events which occurred during 2023.

<i>Komlopteris</i> Extinct genus of seed fern

Komlopteris is an extinct genus of "seed fern" with possible corystosperm affinities. Fossils have been found across both hemispheres, dating from the latest Triassic to the early Eocene (Ypresian), making it the youngest "seed fern" in the fossil record.

References

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  2. ↑ Hilton, J. & Bateman, R. M. (2006), "Pteridosperms are the backbone of seed-plant phylogeny", Journal of the Torrey Botanical Society, 33: 119–168, doi:10.3159/1095-5674(2006)133[119:PATBOS]2.0.CO;2
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  7. ↑ Drinnan A. N.; Schramke J. M.; Crane P. R. (1990). "Stephanospermum konopeonus (Langford) comb. nov: a medullosan ovule from the Middle Pennsylvanian Mazon Creek flora of northeastern Illinois, U.S.A.". Botanical Gazette. 151 (3): 385–401. doi:10.1086/337839. S2CID   84259958.
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  12. ↑ Ramanujam C. G. K.; Rothwell G. W.; Stewart W. N. (1974). "Probable attachment of the Dolerotheca campanulum to a Myeloxylon-Alethopteris type frond". American Journal of Botany. 61 (10): 1057–1066. doi:10.2307/2441923. JSTOR   2441923.
  13. ↑ Poort R.J.; Visscher H.; Dilcher D.L. (1996). "Zoidogamy in fossil gymnosperms: the centenary of a concept, with special reference to pre-pollen of Late Paleozoic conifers". Proceedings of the National Academy of Sciences. 93 (21): 11713–11717. Bibcode:1996PNAS...9311713P. doi: 10.1073/pnas.93.21.11713 . PMC   1074524 . PMID   16594095.
  14. ↑ Basinger J. F.; Rothwell G. W.; Stewart W. N. (1974). "Cauline vasculature and leaf trace production in medullosan pteridosperms". American Journal of Botany. 61 (9): 1002–1015. doi:10.2307/2441991. JSTOR   2441991.
  15. 1 2 Delevoryas T (1955). "The Medullosae--structure and relationships". Palaeontographica, Abteilung B. 97: 114–167.
  16. ↑ Beeler H. E. (1983). "Anatomy and frond architecture of Neuropteris ovata and N. scheuchzeri from the Upper Pennsylvanian of the Appalachian Basin". Canadian Journal of Botany. 61 (9): 2352–2368. doi:10.1139/b83-259.
  17. ↑ Pryor J. S. (1990). "Delimiting species among permineralized medullosan pteridosperms: a plant bearing Alethopteris fronds from the Upper Pennsylvanian of the Appalachian basin". Canadian Journal of Botany. 68: 184–192. doi:10.1139/b90-025.
  18. ↑ Stidd B. M.; Oestry L. L.; Phillips T. L. (1975). "On the frond of Sutcliffia insignis var. tuberculata". Review of Palaeobotany and Palynology. 20 (1–2): 55–66. doi:10.1016/0034-6667(75)90006-8.
  19. ↑ Wagner R. H. (1984). "Megafloral zones of the Carboniferous". Compte rendu 9e Congrès International de Stratigraphie et de Géologie du Carbonifère (Washington, 1979). 2: 109–134.
  20. 1 2 Cleal C. J. (2008). "Palaeofloristics of Middle Pennsylvanian medullosaleans in Variscan Euramerica". Palaeogeography, Palaeoclimatology, Palaeoecology. 268 (3–4): 164–180. Bibcode:2008PPP...268..164C. doi:10.1016/j.palaeo.2008.03.045.
  21. ↑ Laveine J.-P. (1997). "Synthetic analysis of the neuropterids. Their interest for the decipherment of Carboniferous palaeogeography". Review of Palaeobotany and Palynology. 95 (1–4): 155–189. doi:10.1016/s0034-6667(96)00033-4.
  22. 1 2 Laveine J.-P.; Lemoigne Y.; Shanzhen Zhang (1993). "General characteristics and paleobiogeography of the Parispermaceae (genera Paripteris Gothan and Linopteris Presl), pteridosperms from the Carboniferous". Palaeontographica, Abteilung B. 230: 81–139.
  23. 1 2 3 Doweld, Alexander B. (2001). Prosyllabus Tracheophytorum: Tentamen systematis plantarum vascularium (in English and Russian). Moscow: GEOS.
  24. 1 2 Dunn, Michael T.; Mapes, Gene; Rothwell, Gar W. (2002). "On Paleozoic Plants from Marine Strata: Hexaloba Finisensia New Genus and Species, A Trigonocarpalean Ovule from the Virgilian (Upper Pennsylvanian: Gzhelian) Finis Shale of Texas". Journal of Paleontology. 76 (1): 173–180. doi:10.1666/0022-3360(2002)076<0173:OPPFMS>2.0.CO;2. ISSN   0022-3360.
  25. ↑ Spencer, Alan R.T.; Hilton, Jason; Sutton, Mark D. (2013). "Combined methodologies for three-dimensional reconstruction of fossil plants preserved in siderite nodules: Stephanospermum braidwoodensis nov. sp. (Medullosales) from the Mazon Creek lagerstätte". Review of Palaeobotany and Palynology. 188: 1–17. doi:10.1016/j.revpalbo.2012.09.001.
  26. ↑ Taylor T. N.; Eggert D. A. (1967). "Petrified plants from the Upper Mississippian of North America. I: The seed Rhynchosperma gen. n.". American Journal of Botany. 64 (8): 984–992. doi:10.2307/2440722. JSTOR   2440722.
  27. ↑ Mapes G.; Rothwell G. W. (1980). "Quaestora amplecta gen. et ap. n., a structurally simple medullosan stem from the Upper Mississippian of Arkansas". American Journal of Botany. 67 (5): 636–647. doi:10.2307/2442657. JSTOR   2442657.
  28. ↑ DiMichele W. A.; Phillips T. L.; Pfefferkorn H. W. (2006). "Paleoecology of Late Paleozoic pteridosperms from tropical Euramerica". Journal of the Torrey Botanical Society. 133: 83–118. doi:10.3159/1095-5674(2006)133[83:polppf]2.0.co;2.
  29. ↑ Seyfullah L. J.; Hilton J.; Shi-Jun Wang; Galtier J. (2009). "Anatomically preserved pteridosperm stems and rachises from Permian floras of China". International Journal of Plant Sciences. 170 (6): 814–828. doi:10.1086/599076. S2CID   85907996.
  30. ↑ Goganova L. A.; Laveine J.-P.; Lemoigne Y.; Durante M.; et al. (1992). "General characteristics of the Carboniferous pteridosperm Cardioneuropteris Goganova et al., from the uppermost Visean strata of Kuucheku Colliery near Karaganda, central Kazakhstan, CIS". Revue de Paléobiologie, Volume spécial. 6: 167–219.
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