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Cosmochlaina
''Cosmochlaina'' (from Greek: kosmos=ornament; xlaina=wrapper/cloak) is a form genus of nematophyte – an early (Silurian – Devonian) plant known only from fossil cuticles, often found in association with tubular structures. The form genus was put forwards by Dianne Edwards, and is diagnosed by inwards-pointing flanges and randomly oriented pseudo-cellular units. Projections on the outer surface are always present, and sometimes also appear on the inner surface; however, the surface of the cuticle itself is always smooth. The holes in the cuticle are often covered by round flaps, loosely attached along a side. Where ''Nematothallus'' was sometimes used to relate only to tube-like structures, ''Cosmochlaina'' was used in reference to the cuticle fragments. Material discovered later revealed its internal anatomy, which comprises a lichen-like mat of 'hyphae'. It has been suggested that the pores of'' Cosmochlaina ''represent broken-off rhizoids, on the basis that rotting and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematophyte
The Nematophyta or nematophytes are a paraphyletic group of land organisms, probably including some plants as well as algae known only from the fossil record, from the Silurian period until the early Devonian Rhynie chert. The type genus '' Nematothallus'', which typifies the group, was first described by Lang in 1937, who envisioned it being a thallose plant with tubular features and sporophytes, covered by a cuticle which preserved impressions of the underlying cells. He had found abundant disaggregated remains of all three features, none of which were connected to another, leaving his reconstruction of the phytodebris as parts of a single organism highly conjectural. No reproductive or vegetative structures common to the land plants are known, and certain members of the nematophyte plexus (including '' Nemataplexus'', axial conjugations of banded and branching tubes) seem to belong to the fungi. The lack of a clear definition of the nematophytes has led to it being used as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematothallus
''Nematothallus'' is a form genus comprising cuticle-like fossils. Some of its constituents likely represent red algae, whereas others resemble lichens. History of research ''Nematothallus'' was first described by Lang in 1937, who envisioned it being an early thallose land plant with tubular features and sporophytes, covered by a cuticle which preserved impressions of the underlying cells. He had found abundant disaggregated remains of all three features, none of which were connected to another, leaving his reconstruction of the phytodebris as parts of a single organism highly conjectural. Even so, it was picked up by Jonker (1973), who proposed that ''Nematothallus'' represented leaves of ''Prototaxites'', which he interpreted as a red alga. Further work failed to draw together all aspects of the organism: Edwards (1982) and Edwards and Rose (1984) both provided thorough descriptions of the cuticular aspects of the plants, while Pratt ''et al.'' (1978) and Niklas and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acid Maceration
Fossil preparation is the act of preparing fossil specimens for use in paleontological research or for exhibition, and involves removing the surrounding rocky matrix and cleaning the fossil. Techniques Acid maceration Acid maceration is a technique to extract organic microfossils from a surrounding rock matrix using acid. Hydrochloric acid or acetic acid may be used to extract phosphatic fossils, such as the small shelly fossils, from a carbonate matrix. Hydrofluoric acid is also used in acid macerations to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied ( dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it. Film pull The film pull technique is a means of recovering carbonaceous compression fossils for study under transmitted light microscopy. An acid is applied to the surface of the rock to etch away the matrix from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Form Genus
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of science is to move "form taxa" to biological taxa whose affinity is known. Form taxonomy is restricted to fossils that preserve too few characters for a conclusive taxonomic definition or assessment of their biological affinity, but whose study is made easier if a binomial name is available by which to identify them. The term "form classification" is preferred to "form taxonomy"; taxonomy suggests that the classification implies a biological affinity, whereas form classification is about giving a name to a group of morphologically-similar organisms that may not be related. A "parataxon" (not to be confused with parataxonomy), or "sciotaxon" (Gr. "shadow taxon"), is a classification based on incomplete data: for instance, the larval stage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary History Of Plants
The evolution of plants has resulted in a wide range of complexity, from the earliest algal mats, through multicellular marine and freshwater green algae, terrestrial bryophytes, lycopods and ferns, to the complex gymnosperms and angiosperms (flowering plants) of today. While many of the earliest groups continue to thrive, as exemplified by red and green algae in marine environments, more recently derived groups have displaced previously ecologically dominant ones; for example, the ascendance of flowering plants over gymnosperms in terrestrial environments. There is evidence that cyanobacteria and multicellular photosynthetic eukaryotes lived in freshwater communities on land as early as 1 billion years ago, and that communities of complex, multicellular photosynthesizing organisms existed on land in the late Precambrian, around . Evidence of the emergence of embryophyte land plants first occurs in the mid-Ordovician (~), and by the middle of the Devonian (~), many of the featur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian Plants
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
