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Drewria
''Drewria potomacensis'' is a Cretaceous megafossil member of the Gnetales Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three Relict ..., from the Potomac Group, hence its name. It was possibly a shrub. It is the only known species in the genus ''Drewria''. Description Its stems were slender, with opposite and decussate leaves. The leaves were oblong and measured up to long. Its reproductive structures consisted of short, loose spikes arranged in dichasial groups of 3. References Further reading * Friis, Else Marie, Peter R. Crane, and Kaj Raunsgaard Pedersen. Early flowers and angiosperm evolution. Cambridge University Press, 2011. * *Wilson, Karen, and David Morrison, eds. Monocots: Systematics and Evolution: Systematics and Evolution. CSIRO PUBLISHING, 2000. *Pearson, David. New organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnetales
Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three Relict (biology), relict genus, genera: ''Gnetum'' (Family (biology), family Gnetaceae), ''Welwitschia'' (family Welwitschiaceae), and ''Ephedra (genus), Ephedra'' (family Ephedraceae). The earliest unambiguous records of the group date to the Jurassic, and they achieved their highest diversity during the Early Cretaceous. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of small tubes (xylem) that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question, with many recent phylogenies f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geological period of the entire Phanerozoic. The name is derived from the Latin , 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation . The Cretaceous was a period with a relatively warm climate, resulting in high Sea level#Local and eustatic, eustatic sea levels that created numerous shallow Inland sea (geology), inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was largely ice-free, although there is some evidence of brief periods of glaciation during the cooler first half, and forests extended to the poles. Many of the dominant taxonomic gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megafossil
Macrofossils, also known as megafossils, are the preserved remnants of organic beings and their activities that are 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 specimens are macrofossils. Macrofossils come in many varieties and form in various ways depending on their environment and what is being fossilized including plant, fungi and animal remnants. Historical background Etymology The origins of the term macrofossil dates back to 1937 and was first used by G. D. Hanna, a US paleontologist and malacologist. Scientific thought Macrofossils have been subject to analysis since ancient times. Several Greek philosophers used fossilized shellfish to theorize the land was once covered by oceans. Macrofossils of body parts hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Else Marie Friis
Else Marie Friis (born 18 June 1947) is a Danish botanist and paleontologist. She is Professor Emerita in the Department of Geoscience at Aarhus University. Her work has been fundamental in the phylogenetic analysis of angiosperms, with widespread application to reproductive biology. Education and early life The daughter of a bookseller Poul Friis and Marie Møller, she was born in Holstebro, and grew up in Skive, graduating from local school Viborg Katedralskole in 1966. She worked as an au-pair in Paris for a year, becoming interested in geology whilst her brother Henrik was a student in the subject. This inspired her to become an assistant teacher in botany and geology in 1971. In 1975 she earned a Magister's degree in science and in 1980 a Licentiate's degree in science, both from Aarhus University. Research and career Her area of interest is the reproductive biology, phylogeny and palaeoecology of flowering plants based on plant reproductive organs from the Cretaceou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Gymnosperm Genera
Prehistory, also called pre-literary history, is the period of human history between the first known use of stone tools by hominins million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared years ago. It took thousands of years for writing systems to be widely adopted, with writing having spread to almost all cultures by the 19th century. The end of prehistory therefore came at different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. It is based on an old conception of history that without written records there could be no history. The most common conception today is that history is based on evidence, however the concept of prehistory hasn't been completely discarded. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
