pteridosperm การใช้

• Pteridosperms ), megasporangia and perhaps ovules were borne on the surface of leaves.
• Conifers reoccurred in the Early Anisian, followed by the cycads and pteridosperms during the Late Anisian.
• Nowadays, four orders of Palaeozoic seed plants tend to be referred to as pteridosperms : Lyginopteridales, Medullosales, Callistophytales and Peltaspermales.
• In 1935, she published a paper on petrified pteridosperms ( seed ferns ) using the revolutionary cellulose peel techniques developed by Walton in 1928.
• Their discovery attracted considerable attention at the time, as the pteridosperms were the first extinct group of vascular plants to be identified solely from the fossil record.
• During the 20th century the concept of pteridosperms was expanded to include various Mesozoic groups of seed plants with fern-like fronds, such as the Corystospermaceae.
• The heterogeneity of the terrestrial plant communities increased markedly during the Middle Triassic when plant groups like sphenopsids, ferns, pteridosperms, cycadophytes, ginkgophytes and conifers resurfaced and diversified quickly.
• This is particularly useful for extinct seed plant groups whose systematic relationships remain speculative, as they can be classified as pteridosperms with no valid implications being made as to their systematic affinities.
• They were reproductively more sophisticated than most other Palaeozoic pteridosperms, some of which they seem to have out-competed and replaced in the " coal swamp " vegetation during Late Pennsylvanian and Permian times.
• 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.
• 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.
• One of the few characters that may unify the group is that the ovules were borne in a cupule, a group of enclosing branches, but this has not been confirmed for all " pteridosperm " groups.
• The Lyginopteridales became the most abundant group of pteridosperms during Pennsylvanian times the Medullosales took over as the more important of the larger pteridosperms but the Lyginopteridales continued to flourish as climbing ( lianesent ) and scrambling plants.
• The Lyginopteridales became the most abundant group of pteridosperms during Pennsylvanian times the Medullosales took over as the more important of the larger pteridosperms but the Lyginopteridales continued to flourish as climbing ( lianesent ) and scrambling plants.
• Initially it was still thought that they were " transitional fossils " intermediate between the ferns and cycads, and especially in the English-speaking world they were referred to as " seed ferns " or " pteridosperms ".
• Also, from a purely curatorial perspective the term pteridosperms is a useful shorthand for describing the fern-like fronds that were probably produced by seed plants, which are commonly found in many Palaeozoic and Mesozoic fossil floras.
• With regard to the enduring value of the 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 ), bennettites ).
• In more advanced aneurophytaleans such as " Aneurophyton " these vegetative organs started to look rather more like fronds, and eventually during Late Devonian times the aneurophytaleans are presumed to have given rise to the pteridosperm order, the Lyginopteridales.
• In the 19th century the Carboniferous Period was often referred to as the " Age of Ferns " but these discoveries during the first decade of the 20th century made it clear that the " Age of Pteridosperms " was perhaps a better description.
• The quarry was excavated in magnesian limestone, the lowest level of which is an exceptionally fossiliferous marl slate which has yielded the richest and most varied Permian flora in the Britain and is the type locality for the pteridosperm " Pseudoctensis middridgensis ".