Synonyms for protosalvinia or Related words with protosalvinia
Examples of "protosalvinia"
is found in association with conodont elements.
For the present, the relationships of "
" remain uncertain.
However, the tips of "
" branches show evidence of conceptacle-like dips.
is a prehistoric plant found commonly in shale from shoreline habitats of the Upper Devonian period. The name "
" is a misnomer. The name literally means "early Salvinia", and was given in the erroneous belief that the fossils were an earlier form of the living aquatic fern "Salvinia". It is no longer believed that the fossils come from a fern, but deciding exactly what the fossils represent is still a matter of debate. This is surprising when one considers how much is known about the fossils.
" is usually preserved as a compression fossil, it can be difficult to determine whether its anatomy is more like a plant or an alga. Some biochemical evidence favors interpretation as an alga. Lignin and cutin have been found in the thalli, and sporopollenin in the spore walls. The grouping of the spores found in the thallus favors interpretation as a plant. The absence of any stomata on the surface is inconclusive, as all bryophytes lack stomata on the main body of the plant.
Another reason that liverworts are now classified separately is that they appear to have diverged from all other embryophyte plants near the beginning of their evolution. The strongest line of supporting evidence is that liverworts are the only living group of land plants that do not have stomata on the sporophyte generation. Among the earliest fossils believed to be liverworts are compression fossils of "Pallaviciniites" from the Upper Devonian of New York. These fossils resemble modern species in the Metzgeriales. Another Devonian fossil called "
" also looks like a liverwort, but its relationship to other plants is still uncertain, so it may not belong to the Marchantiophyta. In 2007, the oldest fossils assignable to the liverworts were announced, "Metzgeriothallus sharonae" from the Givetian (Middle Devonian) of New York, United States. However, in 2010, five different types of fossilized liverwort spores were found in Argentina, dating to the much earlier Middle Ordovician, around 470 million years ago.
The most likely interpretation of "
" is that it represents either a fossil liverwort or brown alga, although no definitive brown algae have been identified from before the Tertiary period, and examination of the spore structure shows no features in common with living groups of brown algae. The living plant was a thallus with short dichotomous branching. The branches in the largest species were as much as one centimeter across. In some fossils, the branching lobes lie flat, but in others the tips of the branches are curled up over the fossil, giving it a round outline. Embedded in the tissues of the thallus are chambers in which spores (200 micrometre diameter) were produced by meiosis.
Fossils comparable in morphology to brown algae are known from strata as old as the Upper Ordovician, but the taxonomic affinity of these impression fossils is far from certain. Claims that earlier Ediacaran fossils are brown algae have since been dismissed. While many carbonaceous fossils have been described from the Precambrian, they are typically preserved as flattened outlines or fragments measuring only millimeters long. Because these fossils lack features diagnostic for identification at even the highest level, they are assigned to fossil form taxa according to their shape and other gross morphological features. A number of Devonian fossils termed "fucoids", from their resemblance in outline to species in the genus "Fucus", have proven to be inorganic rather than true fossils. The Devonian megafossil "Prototaxites", which consists of masses of filaments grouped into trunk-like axes, has been considered a possible brown alga. However, modern research favors reinterpretation of this fossil as a terrestrial fungus or fungal-like organism. Likewise, the fossil "
" was once considered a possible brown alga, but is now thought to be an early land plant.
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