| Orbisiana Temporal range: Ediacaran | |
|---|---|
Scientific classification  | |
| Kingdom: | incertae sedis |
| Genus: | † Orbisiana Sokolov, 1976 |
| Species | |
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Orbisiana is an Ediacaran benthic organism formed out of series of agglutinated spherical or hemispherical chambers. It is believed to be a close relative of Palaeopascichnus .[ citation needed ]
Orbisiana occur in aggregates made up of rows arranged in sometimes branching chains. [1] 3-D analysis has shown Orbisiana to be cylindrical in shape and open at both the top and bottom ends of its structure. [2] The chains often varied in shape from straight to curved and disorganized lines of spheres with no fixed number of spheres per chain. [2] Specimens range in size but generally have diameters of 0.2–0.9 millimetres (0.0079–0.0354 in). [3] The cell membranes of the organism are often pyritized. [4] The individual chambers are agglutinating. [5]
Two species have been documented, O. linearis and O.simplex. [2] [3] [4] [6] [7]
It fits into the Palaeopascichnids, the other genus being Palaeopascichnus itself. [8]
Over 100 specimens have been collected from the lower Ediacaran Lantian Formation located in Xiuning and Yixian counties of the Anhui Province, China. [2] [7]
Orbisiana was first described by B.S. Sokolov in 1976, found in the Neoproterozoic of Russia. [3] [6]
Orbisiana likely favored calm and well aerated shallow marine habitats in which it could utilize sunlight for benthic photosynthesis. [6]
The Ediacaran period is a geological period of the Neoproterozoic era that spans 96 million years from the end of the Cryogenian period at 635 Mya, to the beginning of the Cambrian period at 538.8 Mya. It is the last period of the Proterozoic eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian period marks the start of the Phanerozoic eon where recognizable fossil evidence of life becomes common.
The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
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.
The Proterozoic is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, the longest eon of the Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozoic, and is the most recent part of the Precambrian "supereon".
Pteridinium is an erniettomorph found in a number of Precambrian deposits worldwide. It is a member of the Ediacaran biota.
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. 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.
Rangea is a frond-like Ediacaran fossil with six-fold radial symmetry. It is the type genus of the rangeomorphs.
Namacalathus is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, N. hermanastes, was first described in 2000 from the Nama Group of central and southern Namibia.
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.
Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately 567 to 550 million years ago. The name comes from the Greek προ = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as Dickinsonia, Vendia, Cephalonega, Praecambridium and currently many other Proarticulata are described.
The end-Ediacaran extinction is a mass extinction believed to have occurred near the end of the Ediacaran period, the final period of the Proterozoic eon. Evidence suggesting that such a mass extinction occurred includes a massive reduction in diversity of acritarchs, the sudden disappearance of the Ediacara biota and calcifying organisms, and the time gap before Cambrian organisms "replaced" them. Some lines of evidence suggests that there may have been two distinct pulses of the extinction event, one occurring 550 million years ago and the other 539 million years ago.
Palaeopascichnus is an Ediacaran fossil comprising a series of lobes, first originating before the Gaskiers glaciation; it is plausibly a protozoan, but probably unrelated to the classical 'Ediacaran biota'. Once thought to represent a trace fossil, it is now recognized as a body fossil and corresponds to the skeleton of an agglutinating organism.
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 and India. Several morphologically distinct species are recognized.
Mezenia is a genus of macroalgae described by Boris Sokolov in 1976. Mezenia lived in Eurasia during the Ediacaran between 560 and 551 Ma.
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.
Nenoxites is an extinct genus of Ediacaran ichnofossils described by Mikhail Fedonkin in 1973. The genus is monotypic; the only species to have been described is Nenoxites curvus.
A "Palaeopascichnid" describes a multitude of elongate fossils made up of multiple sausage-shaped chambers. They appear only in Ediacaran sediments. Fossils of Palaeopascichnids consist of an occasionally branching series of globular or elongate chambers. These fossils started appearing in the Vendian about 580 million years ago. Fossils of Palaeopascichnids are found in East European platform, Siberia, South China (Lantian), Australia, India (Tethys), Avalonia
Shuhai Xiao is a Chinese-American paleontologist and professor of geobiology at Virginia Tech, Blacksburg, Virginia, U.S.A.
Melanocyrillium is a Precambrian genus of vesicle-shaped microfossils of uncertain affinity found in the Grand Canyon Supergroup and Togari Group of Tasmania. M. hexodiadema has been described as a "probable lobose amoeba".