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Callistophytaceae
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 (Kasimovian-Gzhelian; 299.0–306.5 Ma) vegetation of clastic soils and some peat soils. The best known callistophyte was documented from Late Pennsylvanian coal ball petrifactions in North America.Rothwell, G. W. (1981). "The Callistophytales (Pteridospermopsida). Reproductively sophisticated gymnosperms." ''Review of Palaeobotany and Palynology'', 32: 103-121. Description Stems The relatively slender stems (fossil genus ''Callistophyton'') had a eustele with a well-developed zone of secondary wood, and unlike most (but not all)Hamer, J. J. & Rothwell, G. W. (1988). The vegetative structure of ''Medullosa endocentrica'' (Pteridospermopsida). ''Canadian Journal of Bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pteridospermatophyta
The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants (spermatophytes). The earliest fossil evidence for plants of this type is the genus ''Elkinsia'' of the 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 some pteridosperm-like plants seem to have survived into Eocene times, based on fossil finds in Tasmania. With regard to the enduring utility of this division, many palaeobotanists still use the pteridosperm grouping in an informal sense to refer to the seed plants that are not angiosperms, coniferoids (conifers or cordaites), ginkgophytes or cycadophytes (cycads or bennettites). This is particularly useful for extinct seed plant groups whose systematic relationships remain speculative, as they can be classified as pteridosperms with no v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pteridosperms
The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants (spermatophytes). The earliest fossil evidence for plants of this type is the genus ''Elkinsia'' of the 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 some pteridosperm-like plants seem to have survived into Eocene times, based on fossil finds in Tasmania. With regard to the enduring utility of this division, many palaeobotanists still use the pteridosperm grouping in an informal sense to refer to the seed plants that are not angiosperms, coniferoids (conifers or cordaites), ginkgophytes or cycadophytes (cycads or bennettites). This is particularly useful for extinct seed plant groups whose systematic relationships remain speculative, as they can be classified as pteridosperms with no v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axillary Bud
The axillary bud (or lateral bud) is an embryonic or organogenic shoot located in the axil of a leaf. Each bud has the potential to form shoots, and may be specialized in producing either vegetative shoots (stems and branches) or reproductive shoots ( flowers). Once formed, a bud may remain dormant for some time, or it may form a shoot immediately. Overview An axillary bud is an embryonic or organogenic shoot which lies dormant at the junction of the stem and petiole of a plant. It arises exogenously from outer layer of cortex of the stem. Axillary buds do not become actively growing shoots on plants with strong apical dominance (the tendency to grow just the terminal bud on the main stem). Apical dominance occurs because the shoot apical meristem produces auxin which prevents axillary buds from growing. The axillary buds begin developing when they are exposed to less auxin, for example if the plant naturally has weak apical dominance, if apical dominance is broken by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyginopteridales
The Lyginopteridales were the archetypal pteridosperms: They were the first plant fossils to be described as pteridosperms and, thus, the group on which the concept of pteridosperms was first developed;Oliver, F. W. & Scott, D. H. (1904). "On the structure of the Palaeozoic seed ''Lagenostoma Lomaxi'', with a statement of the evidence upon which it is referred to ''Lyginodendron''." ''Philosophical Transactions of the Royal Society of London, Series B,'' 197: 193-247. they are the stratigraphically oldest-known pteridosperms, occurring first in late Devonian strata;Rothwell, G. W., Scheckler, S. E. & Gillespie, W. H. (1989). "''Elkinsia'' gen. nov., a Late Devonian gymnosperm with cupulate ovules." ''Botanical Gazette,'' 150: 170-189. and they have the most primitive features, most notably in the structure of their ovules.Long, A. G. (1959). "On the structure of ''Calymmatotheca kidstoni'' Calder (emended) and ''Genomosperma latens'' gen. et sp. nov. from the Calciferous Sandst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macrofossil
Macrofossils, also known as megafossils, are preserved organic remains large enough to be visible without a microscope. The term ''macrofossil'' stands in opposition to the term microfossil. Microfossils, by contrast, require substantial magnification for evaluation by fossil-hunters or professional paleontologists. As a result, most fossils observed in the field and most "museum-quality" specimens are macrofossils. Varieties Plant macrofossils Plant macrofossils include leaf, needle, cone, and stem debris; and can be used to identify types of plants formerly growing in the area. Such botanical macrofossil data provide a valuable complement to pollen and faunal data that can be used to reconstruct the prehistoric terrestrial environment. Algal macrofossils (for instance, brown kelp, sea lettuce and large stromatolites) are increasingly used to analyze prehistoric marine and aquatic ecosystems. Animal macrofossils Animal macrofossils include the teeth, skulls, and bon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gymnosperm
The gymnosperms ( lit. revealed seeds) 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 el, γυμνόσπερμος ( el, γυμνός, translit=gymnos, lit=naked, label=none and el, σπέρμα, translit=sperma, lit=seed, label=none), literally meaning '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 the surface of scales or leaves, which are often modified to form cones, or solitary as in yew, ''Torreya'', '' Ginkgo''. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the study of the entirety of an organism's lifespan. Ontogeny is the developmental history of an organism within its own lifetime, as distinct from phylogeny, which refers to the evolutionary history of a species. Another way to think of ontogeny is that it is the process of an organism going through all of the developmental stages over its lifetime. The developmental history includes all the developmental events that occur during the existence of an organism, beginning with the changes in the egg at the time of fertilization and events from the time of birth or hatching and afterward (i.e., growth, remolding of body shape, development of secondary sexual characteristics, etc.). While developmental (i.e., ontogenetic) processes can influence sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apical (anatomy)
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes. The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal. Additionally, for some animals such as invertebrates, some terms may not have any meaning at all; for example, an animal that is radially symmetrical will have no anterior surface, but can still have a description that a part is close to the middle ("proximal") or further from the middle ("distal"). International organisations have determined vocabularies that are often used as standard vocabularies for subdisciplines of anatomy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vasculature
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek ''kardia'' meaning ''heart'', and from Latin ''vascula'' meaning ''vessels''). The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit. Some sources use the terms ''cardiovascular system'' and ''vascular system'' interchangeably with the ''circulatory system''. The network of blood vessels are the great vessels of the heart including large elastic arteries, and large veins; other arteries, smaller arterioles, capillaries that join with venules (small veins), and other veins. The circulatory system is closed in vertebrates, which means that the blood never leaves the network of blood vessels. Some invertebrates such as arth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medullosales
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. Their nearest still-living relatives are the cycads. Most medullosales were small to medium-sized trees. The largest specimens were probably of genus '' Alethopteris'', whose fronds could be 7 metres long 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. 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. Ovules Ovules in different medullosalean species could vary from maybe 1 cm to over 10 cm long - the latter being the largest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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