| Medusinites Temporal range: | |
|---|---|
 | |
| Medusinites asteroides from the Ediacaran Ediacara Member of the Rawnsley Quartzite in the Ediacara Hills, South Australia on display at the US. National Museum, Washington | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Genus: | Medusinites |
| Species | |
Medusinites is a genus of disc shaped fossilised organisms associated with the Ediacaran biota. They have been found in rocks dated to be 580 to 541 million years old. [1]
Only three distinct species of Medusinites are known. [1] They are similar to Protolyella in form and have an inner and outer ring. [2] Specimens are typically 1–5 cm in diameter and the radius of its central disc is smaller than the width of the outer ring. [2] They also have radial furrows and concentric circle features, but those details are not always preserved. [2] They have been described as possibly living a lifestyle similar to a "stationary intermediate-level epifaunal osmotroph". [3]
Medusinites species have been found in Australia, Canada, Norway, India, Algeria and Brazil. [1] [4] [5] They are often found in sandstone and quartzite. [6]
Medusinites are in the Phylum Cnidaria, which means they are related to other genera such as Aspidella and Cloudinidae, [7] and are essentially classified as eumetazoans, just like modern jellyfish. [7] However, there have been several differing theories over the years about the placement of Medusinites, as well as the Ediacaran biota as a whole, and how many species there are within the genus. Several species within Medusinites have been moved to other genera or absorbed into other existing species, such as M. patellaris, which was found to be a junior holotype for an Aspidella sp., [4] and M. mawsoni, which was assimilated into M. asteroides . [2] Regarding the debate over the nature of disc shaped Ediacaran fossils like Medusinites, there are two main opposing points of view. A. Seilacher views the theory of them being soft bodied and jellyfish-like as problematic and suggests that they were more likely a unique type of organism that had a "quilted" construction. [8] Another view supported by Grazhdankin and Gerdes is that they were possibly a type of microbial colony. [9]
The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period about 550 million years ago. and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud.
Dickinsonia is a genus of extinct organism, most likely an animal, that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It is one of the best known members of the Ediacaran biota. The individual Dickinsonia typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth has been considered consistent with a stem-group bilaterian affinity, though various other affinities have been proposed. It lived during the late Ediacaran. The discovery of cholesterol molecules in fossils of Dickinsonia lends support to the idea that Dickinsonia was an animal, though these results have been questioned.
Cyclomedusa is a circular fossil of the Ediacaran biota; it has a circular bump in the middle and as many as five circular growth ridges around it. Many specimens are small, but specimens in excess of 20 cm are known. The concentric disks are not necessarily circular, especially when adjacent individuals interfere with each other's growth. Many radial segment lines — somewhat pineapple-like — extend across the outer disks. A few specimens show what might be a stem extending from the center in some direction or other.
Charnia is an extinct genus of frond-like lifeforms belonging to the Ediacaran biota 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; the species name after Roger Mason, a schoolboy who found it. Charnia is significant because it was the first Precambrian fossil to be recognized as such.
Kimberella is an extinct genus of bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious.
Spriggina is a genus of early 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.
Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms 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 period. They became extinct shortly after the so-called Cambrian explosion, with the introduction of fauna forming groups more recognizably related to modern animals, however sponges may be descended from this clade. It is likely that the whole Ediacaran biota is not a monophyletic clade and not every genus placed in its subtaxa is an animal.
Yorgia waggoneri is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of 25 cm (9.8 in). It is classified within the extinct animal phylum Proarticulata.
Ediacaria is a fossil genus dating to the Ediacaran Period of the Neoproterozoic Era. Unlike most Ediacaran biota, which disappeared almost entirely from the fossil record at the end of the Period, Ediacaria fossils have been found dating from the Baikalian age of the Upper Riphean to 501 million years ago, well into the Cambrian Period. Ediacaria consists of concentric rough circles, radial lines between the circles and a central dome, with a diameter from 1 to 70 cm.
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.
Nimbia occlusa is a form of Ediacaran fossil shaped like a circular or oval disk, with a thick rim around the margin. Within the rim the fossil is usually flat, but may have a central nipple or dimple. These fossils were generally believed to be those of cnidarians, but they have since been reinterpreted as structures made by microbial colonies. They can reach up to 6 cm in diameter, with a centimeter-thick rim. Some fossils are distorted.
The Ediacaranbiota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were 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. The term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined.
Arumberia is an enigmatic fossil from the Ediacaran period originally described from the Arumbera Sandstone, Northern Territory, Australia but also found in the Urals, East Siberia, England and Wales, Northern France, the Avalon Peninsula, India and Brazil. Several morphologically distinct species are recognized.
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
The petalonamids (Petalonamae) are an extinct group of archaic animals typical of the Ediacaran biota, also called frondomorphs, dating from approximately 635 million years ago to 516 million years ago. They are benthic and motionless animals, that have the shape of leaves, fronds (frondomorphic), feathers or spindles and were initially considered algae, octocorals or sea pens. It is now believed that there are no living descendants of the group, which shares a probable relation to the Ediacaran animals known as Vendozoans.
Archaeaspinus fedonkini is an extinct proarticulatan organism from the Late Precambrian (Ediacaran) period.
Persimedusites chahgazensis is a Precambrian discoidal species which are believed to have existed primarily during the late Ediacaran period. It was discovered initially in the Kushk Series in the Bafq and Behabad regions of central Iran, along with similarly aged specimen of Cloudina and Corumbella. The body fossils of these disc-shaped organisms are approximately one centimeter in diameter, and were noted to have symmetrical internal lobes, as well as secondary distal branches.
Eoporpita is a disc or ellipse-shaped Ediacaran fossil with unsure taxonomy/classification. It is known from its type species, Eoporpitamedusa, the only species within the genus Eoporpita.
{{cite web}}: Missing or empty |title= (help)