Dickinsonia costata is an enigmatic Ediacaran organism that lived around 560 to 550 million years ago.
Summary
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- 1 Etymology
- 2 Period in which they lived
- 3 Morphology
- 4 Fossilization
- 5 The fossil bodies
- 6 Species studied
- 7 Sources
Etymology
Dickinsonia costata was first described by Reg Sprigg , he was the original discoverer of the Ediacara biota in Australia , named after Ben Dickinson, then Director of Mines for South Australia , and the head of the government department employing Sprigg .
Period in which they lived
Organisms Ediacarans , also known as biota period Ediacarian or above, biota or wildlife Vendian are ancient life sessile tubular shaped and sheet inhabited the earth during the period Ediacarian (ago c. 635-542 million years) and that they represent the oldest known complex multicellular organisms within the macrocellular level of biological complexity .
Morphology
Dickinsonia costata had stripes or segments on the body, it was wide and oval, fossils have been found reaching up to 1 m in length, and from a fraction of a millimeter to a few millimeters thick. They are bilaterally symmetrical, segmented, round or generally oval, slightly enlarged at one end. The segments are inclined radially towards the wide and narrow ends, the width and length of the segments increases towards the wide end of the fossil. The segments are separated by a thin crest or groove along the axis of symmetry in right and left halves.
His identity is a matter of controversy; some think it was a segmented flat worm , others that it was a soft coral , and some believe it was a jellyfish , many have even argued that they were lichens .
Fossilization
The conservation of these fossils is considered a fascinating scientific enigma, since being soft-bodied organisms, they would not normally fossilize. Unlike other later soft-bodied life forms (such as those of Burgess shale or Solnhofen limestone ), ediacary organisms were not located in restricted environments subject to unusual local conditions, but were a global phenomenon. Therefore, the processes involved in fossilization must have been systematic and present throughout the world.
There must have been something very different in the Ediacaric period that allowed these delicate creatures to be preserved. The most widespread hypothesis is that the fossils were preserved thanks to the fact that they were quickly covered by ash or sand , trapping them next to the mud or the microbe mats in which they lived. The ash layers offer more fossil details and can be accurately dated with a margin of error of a million years or less by radiometric dating.
Fossil bodies
As a general rule, the Dickinsonia fossils are preserved as a negative impression on the bed bases of [[sandstone. Such fossils are traces of the upper sides of the benthic organisms that have been buried under the sand . The impressions formed as a result of the cementation of the sand before the complete decomposition of the body.
The mechanism of the foundation is not entirely clear, among many possibilities, the process could have arisen from the conditions that gave rise to the “death masks” of pyrite on the decomposing body, or perhaps it was due to cementation of carbonate from the sand. The tracks of the bodies of the organisms are often strongly compressed, distorted, and sometimes partially spread on the overlying rock. These deformations appear to demonstrate attempts by organisms to escape sediment fall.
Species studied
Since 1947, a total of nine species have been described:
- Dickinsonia costata Sprigg, 1947 (type species)
- Dickinsonia Sprigg Minima, 1949
- Dickinsonia spriggi Harrington and Moore, 1955
- Dickinsonia elongata Glaessner and Wade, 1966
- Dickinsonia tenuis Glaessner and Wade, 1966
- Dickinsonia lissa Wade, 1972
- Dickinsonia Brachina Wade, 1972
- Dickinsonia menneri Keller
- Dickinsonia tenuis (junior synonym D. Brachina). Very similar to Dickinsonia costata but differs from it by narrower and more numerous segments, with moderately elongated oval body shape.