Ovuliferous Organs Research Articles

The reproductive biology of glossopterid gymnosperms—A review

We review recent advances on glossopterid reproductive biology and their implications for seed plant phylogeny and the ecology of this widespread Permian Gondwanan group. Microsporangiate organs are interpreted to have been arranged in loose compound cones—an organization that evokes comparisons with Ginkgoales, Cordaitales and early conifers. The pollen was typically taeniate, bisaccate, and primarily adapted to wind dispersal. The diverse ovuliferous organs generally incorporated some form of marginal flange or wing. In most cases, the wing was probably protective, wrapping around the ovules during early development. However, we postulate that some conspicuous flanges were potentially analogous to angiosperm petals, functioning as corolla-like guides to attract insect pollinators. The arrangement of seed-bearing polysperms adnate to the subtending leaf to form a fertiliger in glossopterids represented another means of protecting the ovules. In some cases, highlighting the polysperm against the attached leaf might have increased the showiness of the ovule-bearing part for pollinators. In other cases, detachment of the fertiliger may have aided anemochory by retarding seed fall through rotation analogous to dispersal in extant Tilia. The microgametophyte in glossopterids is characterized by a short, weakly branched, haustorial tube, and the release of motile sperm cells. At least some seeds of glossopterids express polyembryony. Mature seeds possessed various micropylar modifications for the entrapment of pollen, and winged or bulbous expansions of the outer integument to aid anemochory or possibly hydrochory. Vegetative regeneration as a response to damage occurred via epicormic buds and possibly by the development of lignotubers.

The architecture of Permian glossopterid ovuliferous reproductive organs

McLoughlin, S. & Prevec, R. 20 September 2019. The architecture of Permian glossopterid ovuliferous reproductive organs. Alcheringa XX, xxx–xxx. ISSN 0311-5518A historical account of research on glossopterid ovuliferous reproductive structures reveals starkly contrasting interpretations of their architecture and homologies from the earliest investigations. The diversity of interpretations has led to the establishment of a multitude of genera for these fossil organs, many of the taxa being synonymous. We identify a need for taxonomic revision of these genera to clearly demarcate taxa before they can be used effectively as palaeobiogeographic or biostratigraphic indices. Our assessment of fructification features based on extensive studies of adpression and permineralized fossils reveals that many of the character states for glossopterids used in previous phylogenetic analyses are erroneous. We interpret glossopterid fertiligers to have been borne in loose strobili in which individual polysperms represent fertile cladodes of diverse morphologies subtended by a vegetative leaf or bract. Polysperms within the group are variously branched or condensed with ovule placement ranging from marginal to abaxial, in some cases occurring on recurved branchlets or in cupule-like structures. Glossopterid polysperms of all types are fringed by one or two ranks of wing-like structures that may represent the remnants of megasporophylls that were, ancestrally, developed on the fertile axillary shoot. Glossopterid fertiligers have similarities to the condensed bract/ovuliferous scale complexes of conifer cones, but comparisons with Mesozoic seed-ferns are hindered by insufficient data on the arrangement and homologies of the ovule-bearing organs of the latter group. Nevertheless, glossopterid polysperms differ from the ovuliferous organs of Mesozoic seed-ferns by longitudinal versus transverse folding, respectively.Stephen McLoughlin* [steve.mcloughlin@nrm.se], Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden; Rose Prevec [r.prevec@am.org.za], Department of Earth Sciences, Albany Museum, 40 Somerset Street, Makhanda, 6139, Eastern Cape, South Africa, and Department of Botany, Rhodes University, PO Box 94, Makhanda, 6140, Eastern Cape, South Africa.

Ovuliferous Organs of Trisquamales Gordenko et Broushkin ordo. nov. (Gymnospermae) from the Middle Jurassic of the Kursk Region, European Russia

The ovuliferous organs Trisquama valentinii Gordenko et Broushkin, gen. et sp. nov. from the Bathonian deposits of the Mikhailovskii Rudnik locality (Kursk Region) are described. The ovuliferous organs consist of three scales fused at the base. The long scale, together with the stalk of ovuliferous organ compose a sterile structure, which is vascularized by C-shaped in section collateral vascular bundle, and bears a lobed fertile structure of ovuliferous organ on its anatomically abaxial side. The latter consists of two short scales and an outgrowth between them, and is vascularized by concentric amphicribral vascular bundle, which is divided in its distal part into three separate collateral plates. These plates are associated with the lobes of fertile structure and three small orthotropous seeds situated from xylem side of these vascular bundles. Seeds are ellipsoidal, with not protruding micropyle; the integument is sclerified, megaspore membrane is thick. The ovuliferous organs under description possess unique features, which preclude their assignment to any large group of gymnosperms; authors place them in a separate order, Trisquamales ordo. nov., systematic position of which within Gymnospermae is uncertain.

Westersheimia pramelreuthensis from the Carnian (Upper Triassic) of Lunz, Austria: More Evidence for a Unitegmic Seed Coat in Early Bennettitales

Premise of research. Isolated ovules and dispersed seeds have been obtained from bulk macerations of carbonaceous shales bearing fossil plants from the Carnian (Upper Triassic) flora of Lunz am See, Austria. Through cuticle analysis, these well-preserved specimens were identified as ovules, interseminal scales, and seeds of Westersheimia pramelreuthensis, a peculiar bennettitalean ovuliferous organ. The preservation of several cuticular layers enables for interpretation of the architecture of the ovules and seeds.Methodology. The excellently preserved plant fossils were investigated using LM and epifluorescence microscopy of cuticles. For comparison, the architecture of ovules and seeds of bennettitalean reproductive organs from Scania (Sweden), Jameson Land (Greenland), and Yorkshire (United Kingdom) were reevaluated.Pivotal results. The preserved layers indicate that the nucellus is surrounded by an integument, whose apical end constitutes the micropyle. The single integument constitutes the monolayered...

New interpretation of seeds Grenana Samylina (Gymnospermae) from the Middle Jurassic of Angren, Uzbekistan

The seeds described by Samylina (1990) from the Middle Jurassic of Angren (Uzbekistan) as Grenana angrenica are revised. Samylina also described under this name the ovuliferous organs and leaves found in the same locality in association with these seeds, selected a leaf specimen as a holotype, and interpreted G. angrenica as a peculiar seed fern. The revision shows that the seeds exhibit structure characteristic of the Ginkgoales. The seeds, leaves, and ovuliferous organs were not found in organic connection with one another. Therefore, they cannot be described under the same name, despite the considerable similarity in epidermal-cuticular features. The dispersed seeds of ginkgoalean affinity are usually attributed to the genus Allicospermum Harris. On the basis of reexamination of the Angren material, a new species, Allicospermum budantsevii sp. nov., is described.

A new genus Navipelta (Peltaspermales, Pteridospermae) from the Permian/Triassic boundary deposits of the Moscow syneclise

A new genus of peltaspermalean ovuliferous organs Navipelta gen. nov. is described from the terrestrial deposits of the Nedubrovo locality (village of Nedubrovo, Vologda Region, Russia), belonging to the base of Vetlugian Group (Upper Permian-Lower Triassic). Data on the anatomy of the peltate bilateral ovuliferous organs are obtained for the first time. Vascular strands in the peltoid depart from that of a stalk and branch up to three times distally. Transfusion tissue around the vascular strands is well developed. The new genus had a system of radially arranged resin canals, broaden into large secretory cavities.

Nystroemiaceae, a new family of Permian gymnosperms from China with an unusual combination of features

Nystroemiaceae is proposed as a new family of gymnosperms from the Permian of Cathaysia that adds to the diversity of gymnosperms known from this critical time in seed plant evolution. This family is characterized by bifurcating and highly branched pinnate ovuliferous organs bearing bicornute ovules (seeds) and entire leaves with anastomozing veins that are born on complex and modern-looking branching systems with clear axillary branching. The reconstruction is based on numerous large specimens from two localities in North China, in which the different plant parts are attached to each other. The ovulate structures show some apparently plesiomorphic (primitive) character states more typical of early seed plants, whereas the leaves and branches show the clearly apomorphic (derived) character states of broad-leaved gymnosperms.

A new Late Cretaceous ginkgoalean reproductive structure Nehvizdyella gen. nov. from the Czech Republic and its whole‐plant reconstruction

During the Mesozoic Era, gingkoaleans comprised a diverse and widespread group. Here we describe ginkgoalean fossils in their facies context from the Late Cretaceous (Cenomanian) Peruc-Korycany Formation of the Czech Republic and present a reconstruction of tree architecture and ecology. Newly described in this study is the ovuliferous reproductive structure, Nehvizdyella bipartita gen. et sp. nov. (Ginkgoales). This ovuliferous organ consists of a bifurcating axis, terminated by large cupule-like structures, probably homologous to the collar of the recent Ginkgo. Each cupule encloses an orthotropous ovule. In specimens with the early developmental stages preserved, the entire ovule and young seed, with the exception of the micropylar area, is embedded in the cupule. Mature seeds consist of sclerotesta and sarcotesta. Monosulcate pollen grains of Cycadopites-type are found adhering to the seeds. Although similar to Ginkgo in terms of its large size and reduced number of seeds, N. bipartita differs from the extant genus in having ovules completely enclosed in a cupule-like structure. The co-occurrence of N. bipartita with ginkgoalean leaves of Eretmophyllum obtusum (Velenovský) Kvaček, J., ginkgoalean short shoots of Pecinovicladus kvacekii Falcon-Lang, and ginkgoalean trunk wood of Ginkgoxylon gruettii Pons and Vozenin-Serra in monodominant taphocoenoses at four geographically distant localities suggests that these remains all belong to one plant. This is supported by the close morphological and anatomical similarity between the different organs. Facies analysis of plant assemblages indicates that our Cretaceous tree occupied a water-stressed coastal salt marsh environment. It therefore represents the first unequivocal halophyte among the Ginkgoales.

Discovery of organic connection ofChiropteris Kurr andNystroemia Halle from Early Permian of western Henan, China

Nystroemia reniformis (Kawasaki) comb. nov. is proposed based on specimens showing organic connections betweenChiropteris reniformis Kawasaki andNystroemia pectiniformis Halle from the Lower Permian of Dengfeng in Henan. Vegetative leaf has a long petiole, reniformed, cordate at the base, entire or slightly undulate at the margin; veins are fine, bifurcating repeatedly and finally becoming reticulate and forming polygonal or rhomboidal meshes. Fertile shoot arises from bract axils. The form of the bract is identical to that of a vegetative leaf. Ovuliferous organ arises from the axil of leafy organ, or in other case, both ovuliferous and leafy organs irregularly arise from the axis of the fertile shoot respectively. Numerous bicornute platyspermic seeds are arranged in two rows, obconical, with micropyle pointing upwards. It may represent a new extinct gymnosperms.

Lepidopteris callipteroides, an earliest Triassic seed fern of the Sydney Basin, southeastern Australia

Earliest Triassic shales in the Coal Cliff Sandstone, Caley Formation, Widden Brook Conglomerate and Dooralong Shale (all basal Narrabeen Group) of the Sydney Basin contain a low diversity fossil flora that survived the greatest mass extinction of all time at the Permian-Triassic boundary. Only one species of seed fern is known from this flora and its affinities were unclear until discovery of its reproductive organs and complete large leaves. An ovuliferous reproductive organ, Peltaspermum townrovii sp. nov., can be attributed to the same plant as the leaves because of their identical stomatal apparatus, which is cyclocytic with papillae overhanging the stomatal pit. Polleniferous organs, Permotheca helbyi sp. nov., may have belonged to the same plant, but are only linked by evidence of association on the same bedding plane yielding no other gymnosperms. Pollen masses found within the polleniferous organ include grains identified as Falcisporites australis (de Jersey) Stevens (1981) when found dispersed. The leaves of this plant have long been enigmatic and attributed to ‘Thinnfeldia’ callipteroides or ‘Dicroidium’ callipteroides; however, these genera had very different cuticular structure. Reassessment of the frond architecture of this plant, based on a large, nearcomplete specimen together with information from cuticles and ovuliferous organs, allows reassignment to Lepidopteris callipteroides (Carpentier) comb. nov. The remarkable cuticle thickness, small stomatal size and low stomatal index of these leaves reflect a time of unusually high atmospheric concentrations of carbon dioxide. This plant was an invader of the Sydney Basin from northern Gondwana, spreading southward during the post-apocalyptic earliest Triassic greenhouse.

Discovery of Latest Carboniferous–Early Permian radially symmetrical peltaspermaceous megasporophylls from Europe and North Africa

Abstract In recent years several types of peltaspermaceous ovuliferous organs were described from the Permian of the Northern Hemisphere. The earliest peltasperms had fan-shaped bilaterally symmetrical megasporophylls. In this note, we describe radially symmetrical ovuliferous discs discovered for the first time in the Lower Rotliegend of the Saar–Nahe Basin, Germany (Latest Carboniferous), and the uppermost Lower Permian of Central Morocco. The implications of such discoveries in terms of early peltasperm radiation and geographic distribution are discussed.

Aspects of Permian palaeobotany and palynology. XV. On the oldest known peltasperms with radially symmetrical ovuliferous discs from the Kungurian (uppermost Lower Permian) of the Fore-Urals (Russia)

Peltaspermum retensorium (Zalessky) Naugolnykh et Kerp, comb. nov., a new representative of the Peltaspermales, is described from the Kungurian of the Fore-Urals. Peltaspermum retensorium has radially symmetrical ovuliferous discs. The pollen organs are similar to those of other peltasperms. With regard to the frond architecture and the cuticle, the foliage of this plant appears to be very similar to that of Autunia Krasser emend. Kerp, a genus of peltasperms with bilaterally symmetrical megasporophylls, known from the uppermost Carboniferous and Lower Permian. Peltaspermum retensorium is the oldest true peltasperm with radially symmetrical ovuliferous organs known from Angaraland.

Aspects of Permian palaeobotany and palynology. XI. On the recognition of true peltasperms in the Upper Permian of Western and Central Europe and a reclassification of species formerly included in Peltaspermum Harris

Foliage and ovuliferous organs of a Late Permian representative of the family Peltaspermaceae are described and discussed. The sterile foliage belongs to the well known species Lepidopteris (al. Callipteris) martinsii (Germar) Townrow. Correlated ovuliferous organs consist of radially symmetrical peltate discs, assign able to the form-genus Peltaspermum Harris. In this study emphasis has been given to the recognition of natural taxa. Detailed study of foliage correlated with the formgenus Peltaspermum has resulted in an emendation of the genus and its promotion to a natural status. The classification of species previously included in Peltaspermum is also discussed. Two other natural genera of the family Peltaspermaceae are discussed, viz. Peltaspermopsis Gomankov emend. and Meyenopteris nov. gen. Dispersed radially symmetrical ovuliferous discs of peltaspermaceous affinity, which cannot be interpreted in terms of natural taxa, are transferred to the form-genus Lopadangium Zhao. Autuniopsis nov. gen. is established as a form-genus for bilaterally symmetrical ovuliferous discs of peltaspermaceous affinity. The following combinations are formally introduced: Peltaspermum martinsii (Germar) nov. comb., P. ottonis (Göppert) nov. comb., Meyenopteris natalensis (Thomas) nov. comb., Lopadangium dafengshanense (Wang Ziq. et Wang Lix.) nov. comb. L. madygenicum (Dobruskina) nov. comb., L petchoricum (Chramova) nov. comb., L. usense (Dobruskina) nov. comb. and Autuniopsis dzungarica (Salmenova) nov. comb. The diagnosis of Peltaspermum martinsii is given and since foliage and ovuliferous organs have previously been described under various names a synonymy list is given. The frond architecture, variation in pinnule morphology and epidermal anatomy, palaeoecology and geographical distribution of Peltaspermum martinsii are discussed and the species is compared with other Late Permian callipterids.

Aspects of Permian palaeobotany and palynology. X. The West- and Central European species of the genus Autunia Krasser emend. Kerp (Peltaspermaceae) and the form-genus Rhachiphyllum Kerp (Callipterid Foliage)

A discussion of the West- and Central European species of the natural genus Autunia Krasser emend. Kerp and the form-genus Rhachiphyllum Kerp is presented. These genera include a number of species formerly included in the form-genus Callipteris Brongniart non Bory. The material investigated mainly originates from the Rotliegend (?Upper Carboniferous-Lower Permian) of the Saar-Nahe Basin (F.R.G.). Some of the localities have yielded abundant, apparently more or less autochthonously deposited material. In addition specimens from France, the German Democratic Republic, Poland and Czechoslovakia have been studied. Within the natural genus Autunia, attributable to the family Peltaspermacea Thomas, two species are recognized: Autunia conferta (Sternberg) Kerp and A. naumannii (Gutbier) Kerp. Foliage and reproductive structures are described and discussed. With regard to a natural classification special attention is given to the organization of the ovuliferous organs. The genus is characterized by bilaterally symmetrical megasporophylls with abaxially attached ovules. The polliniferous organs consist of small elongate sporangia attached to peltate megasporophylls. The foliage of Autunia consists of bipinnate to tripinnate fronds with alethopteroid pinnules and equally shaped intercalary pinnules. Autunia is thus far the oldest known peltasperm. The form-genus Rhachiphyllum is characterized by its bipinnate to tripinnate fronds with entire-margined to pinnately lobed alethopteroid normal and rachial pinnules. Six species have been assigned to Rhachiphyllum, viz. R. curretiensis (Zeiller) Kerp, R. diabolica (Zeiller) Kerp, R. lyratifolia (Göppert) Kerp, R. schenkii (Heyer) Kerp and R. subauriculata (Weiss) Kerp. The foliage of Autunia conferta and some species of Rhachiphyllum, e.g., R. schenkii (Heyer) Kerp appears to be very variable. The intraspecific variability of these species could be determined. Variations in foliar morphology partly depend on the stage of development of the plant and the frond. Also ecological factors may have influenced the development of the frond. In the literature there exists a considerable confusion about the specific delimitation of the species treated. A number of the callipterid species previously introduced in the palaeobotanical literature appear to be synonymous with the here accepted and described taxa. The traditional concept of the importance of callipterids in chronostratigraphy and biostratigraphy cannot be maintained. The group has a potential in ecostratigraphical considerations.

ASPECTS OF PERMIAN PALAEOBOTANY AND PALYNOLOGY. VI. TOWARDS A FLEXIBLE SYSTEM OF NAMING PALAEOZOIC CONIFERS

SUMMARY A natural classification of extinct conifers requires the recognition of natural taxa. In conifers reproductive organs provide the most successful characters for delimiting natural genera and families. Based on assembled species, a genus should at least be diagnosed in terms of overall morphology of leafy shoots in combination with the organization of ovuliferous organs. In addition, detailed statements about the epidermal structure are of great practical value. However, most taxa of fossil conifer remains are artificial by implication. Most genera are form-genera, established for all kinds of isolated organs. They have a highly variable degree of artificiality, ranging from taxa comprising fragments which only supposedly belong to conifers, to taxa which can be attributed to a natural family. Fossil conifer taxonomy should recognize the variable status of the taxa to which plant fragments may be assigned. Within a framework of natural genera and varied form-genera, it is possible to integrate taxonomic progress through a “promotion” of taxa. If better preserved material permits a more thorough analysis, species may be transferred to more precisely defined form-genera or even to a natural genus. Some form-genera may gain a natural status through adequate redefinition. Such a flexible procedure is introduced as a possibility to rationalize Late Carboniferous – Permian conifer taxonomy. Within the Walchiaceae one may recognize the three natural genera Walchia Sternberg, Ernestiodendron Florin and Ortiseia Florin. Form-genera explicitly related to this family are Culmitzschia Ullrich (foliage with preserved epidermal structure), Walchiostrobus Florin (ovuliferous organs) and Walchianthus (polliniferous organs). The present state of species assignment is reviewed. The new form-genus, Hermitia Kerp et Clement-Westerhof is established in order to accommodate part of the many species, formerly assigned to Walchia, which can only be diagnosed in terms of overall leaf morphology; the included species are not explicitely related to the Walchiaceae. The following new combinations are introduced (Kerp et Clement-Westerhof): Culmitzschia parvifolia, Hermitia arnhardtii, H. bertrandii, H. carpentieri, H. dawsonii, H. gallica, H. geinitzii, H. germanica, H. imbricatula, H. minuta, H. rigidula, H. schlotheimii, H. schneideri, H. stephanensis, and H. whitei.

THE SO-CALLED “MEGASPOROPHYLL” OF CYCAS - A MORPHOLOGICAL MISCONCEPTION.ITS BEARING ON THE PHYLOGENY AND THE CLASSIFICATION OF THE CYCADOPHYTA

1 The morphological interpretation of the female reproductive organ of Cycas, traditionally a primitive form of a fertile leaf homologue or “megasporophyll”, is reconsidered in the light of typological and phylogenetic evidence. 2 The inquiry into the nature of this so-called “megasporophyll” emphasizes its aberrant structure and in spite of the incongruity in appearance requires its homology with the female “strobilus” of all other Cycadales. 3 The homology of the “megasporophyll” with a cycadalean “strobilus” cannot be accepted without certain restrictions, because it is not subtended by a bract. 4 The paradoxal situation can only be explained by the pseudo-phyllosporous nature of the “megasporophyll” produced by the merging of a “strobilus” and its bract, the resulting structure, by exhibiting a mixture of the characteristics of both the axial ovuliferous organ and the foliar bract, assuming an unusual and typologically incongruous shape reminiscent of a teratological case. 5 The re-assessment of the phylogenetic and taxonomic relationships between the genus Cycas and the other Cycadales indicates that this aberrant form is advanced rather than primitive in respect of its near allies. 6 The alternative interpretation of the reproductive organs of the Cycadales has been discussed in connection with its bearing on the morphology and the phylogeny of other cycadopsid groups, and the existence since early Mesozoic times of an independent hologeny leading to the living cycads is postulated. 7 The diversity of the recent Cycadales most probably reflects an early separation of their ancient lineage into several minor lines of descent.

Ovuliferous Structures of Taxus canadensis

1. The ovuliferous bud arises in the axil of a leaf early in the season, and matures the next year. 2. The ovuliferous organ consists of the primary shoot and the secondary shoot with the ovule. 3. The primary shoot is to be regarded as a vegetative branch of limited growth, bearing only reproductive axes (secondary shoots). While of limited character, at times it may become a functional vegetative shoot like any other vegetative branch. 4. The primary shoot is a persistent structure, functional for several successive seasons. 5. Occasionally the primary shoot may be terminal to a leafy branch. 6. The secondary shoot consists of three pairs of decussate scales and a terminal ovule. 7. The ovule arises as a direct continuation of the axis, there being nothing in its origin to indicate that it is a lateral structure. 8. The archesporium arises from the hypoderm. The sporogenous tissue consists of a considerable mass of cells, out of which one or two may function as megaspore mother cells. 9. The aril is regarded as the morphological fleshy layer of a 3-layered seed coat, delayed in appearance and physically separate from the hard stony layer. 10. The ovule receives its vascular supply direct from the axis cylinder, contrary to any axillary nature, and in harmony with the view that it is a cauline structure.