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Dickinsonia is an extinct genus of basal animal that lived during the late Ediacaran period in what is now Australia, China, India, Russia and Ukraine. The individual Dickinsonia typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth is consistent with a stem-group bilaterian affinity, though some have suggested that it belongs to the fungi, or even an "extinct kingdom". The discovery of cholesterol molecules in fossils of Dickinsonia lends support to the idea that Dickinsonia was an animal.
Charnia is a genus of frond-like Ediacaran lifeforms with segmented, leaf-like ridges branching alternately to the right and left from a zig-zag medial suture. The genus Charnia was named after Charnwood Forest in Leicestershire, England, where the first fossilised specimen was found. Charnia is significant because it was the first Precambrian fossil to be recognized as such.
A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the large leaves of cycads, as well as palms (Arecaceae) and various other flowering plants, such as mimosa or sumac. "Frond" is commonly used to identify a large, compound leaf, but if the term is used botanically to refer to the leaves of ferns and algae it may be applied to smaller and undivided leaves.
The rangeomorphs are a form taxon of frondose Ediacaran fossils that are united by a similarity to Rangea. Some researchers, such as Pflug and Narbonne, suggest that a natural taxon Rangeomorpha may include all similar-looking fossils. Rangeomorphs appear to have had an effective reproductive strategy, based on analysis of the distribution pattern of Fractofusus, which consisted of sending out a waterborne asexual propagule to a distant area, and then spreading rapidly from there, just as plants today spread by stolons or runners.
Spriggina is a genus of early bilaterian animals whose relationship to living animals is unclear. Fossils of Spriggina are known from the late Ediacaran period in what is now South Australia. Spriggina floundersi is the official fossil emblem of South Australia. It has been found nowhere else. The organism reached about 3–5 centimetres (1.2–2.0 in) in length and may have been predatory. Its bottom was covered with two rows of tough interlocking plates, while one row covered its top; its front few segments fused to form a "head."
Vendobionts or Vendozoans (Vendobionta) are a group of benthic beings made up of the majority of extinct creatures that were part of the Ediacaran biota. It is a hypothetical group and at the same time, it would be the oldest of the animals that populated the Earth about 580 million years ago, in the Ediacaran or Vendic period. They became extinct when the so-called Cambrian explosion appeared, with the introduction of fauna formed by more recognizable groups and more related to modern animals.
Hiemalora is a fossil of the Ediacaran biota, reaching around 3 cm in diameter, which superficially resembles a sea anemone. The genus has a sack-like body with faint radiating lines originally interpreted as tentacles, but discovery of a frond-like structure seemingly attached to some Heimalora has added weight to a competing interpretation: that it represents the holdfast of a larger organism. This interpretation would stand against its original classification in the medusoid Cnidaria; it would also consign a once-popular hypothesis placing Hiemalora in the chondrophores, on the basis of its tentacle structure, to the dustbin. Studies testing the feasibility of hypothesis investigated the possibilities that such fragile tentacles could be preserved, and concluded that it would be very improbable — especially as many Hiemalora bearing beds also contain such fossils as Cyclomedusa, but do not preserve the tentacles on these organisms.
Rangea is a frond-like Ediacaran fossil with six-fold radial symmetry. It is the type genus of the rangeomorphs.
Aspidella is an Ediacaran disk-shaped fossil of uncertain affinity. It is known from the single species A. terranovica.
Bradgatia linfordensis is a bush-like Ediacaran fossil. It consists of six or more fronds radiating from a central anchor point at the base. It superficially resembles a compressed cabbage in appearance, although in reality it had a more intricate, fractal mode of organisation. When multiple fossils are found together they are regularly spaced out rather than randomly distributed. It dominates the ecosystem at 8 to 22 cm above the mud surface at the bottom the sea where it grew. It was over-towered by Charnia and Charniodiscus which grew nearby.
Swartpuntia is a monospecific genus of erniettomorph from the terminal Ediacaran period, with at least three quilted, leaf-shaped petaloids — probably five or six. The petaloids comprise vertical sheets of tubes filled with sand. Swartpuntia specimens range in length from 12 to 19 cm, and in width from 11.5 to 140 cm. The margin is serrated, with a 1 mm wide groove. A 14 mm wide stem extends down the middle, tapering towards the top, and stopping 25 mm from the tip. The stem has a V shaped ornamentation on it. The original fossils were found at, and named after, the Swartpunt farm between Aus and Rosh Pinah in Namibia. The generic name comes from Swartpunt, meaning black point in reference to the colour of the rocks. The specific name germsi honours Gerard Germs, who studied the Nama formation of geological beds.
Bomakellia kelleri is an Ediacaran fossil organism represented by only one specimen approximately 9 cm long from the Ust'-Pinega Formation of the Syuzma River and it has similarity to Mialsemia semichatovi from Yorga Formation of the Ediacaran (Vendian) siliciclastic sediments exposed on the Zimnie Gory locality, White Sea of northern Russia and these rocks are dated 555 million year old.
Thaumaptilon is a fossil genus of animals from the middle Cambrian Burgess Shale which some authors have compared to members of the Ediacaran biota, generally believed to have disappeared at the start of the Cambrian, 542 million years ago. It was up to 20 cm long, and attached itself to the sea floor with a holdfast.
The Ediacaranbiota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were composed of enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms.
Pectinifrons was a rangeomorph, a member of the Ediacara biota found at Mistaken Point, Newfoundland.
Primocandelabrum is a genus of rangeomorph known from the Avalon-type Ediacaran biota. It makes up the brunt of some bedding plane assemblages. Primocandelabrum was described by Hofmann, O'Brien, and King in 2008.
Beothukis mistakensis is a rare fossil frond-like member of the Rangeomorpha, described from the Ediacaran of Mistaken Point, Newfoundland. It had been identified since 1992, referred in papers as a "spatulate frond" or "flat recliner", but not formally described until 2009. The original fossils from which the genus has been described are still in situ, but replicas are preserved at the Memorial University of Newfoundland and at the Oxford University Museum of Natural History. Claims of a stem have been contentious, and based largely on structures that have subsequently been determined to be erosional scours, and is so considered to be a recliner
Parviscopa is a genus of frondose forms characterized in 2008 based on specimens from Newfoundland, Canada. Parviscopa is a member of the Ediacaran biota, and is more specifically part of the Avalon type assemblage, which is from the older part of the Ediacaran and is characterized by deep water deposits.
Frondosity is the property of an organism that normally flourishes with fronds or leaf-like structures.
References
- 1 2 3 4 Narbonne, G. M.; Laflamme, M.; Greentree, C.; Trusler, P. (2009). "Reconstructing a Lost World: Ediacaran Rangeomorphs from Spaniard's Bay, Newfoundland". Journal of Paleontology. 83 (4): 503. doi:10.1666/08-072R1.1.
- ↑ Brasier, M. D.; Liu, A. G.; Menon, L.; Matthews, J. J.; McIlroy, D.; Wacey, D. (2013). "Explaining the exceptional preservation of Ediacaran rangeomorphs from Spaniard's Bay, Newfoundland: A hydraulic model". Precambrian Research. 231: 122. doi:10.1016/j.precamres.2013.03.013.
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