Vernanimalcula
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| Vernanimalcula guizhouena | ||||
|---|---|---|---|---|
| Scientific classification | ||||
|
Vernanimalcula has been described as the earliest known member of the Bilateria (animals with bilateral symmetry). It lived some 580 to 600 million years ago. It was between 0.1 and 0.2 mm across (roughly the width of one or two human hairs), and probably fed on microbes on the sea floor. It may have moved over the sea floor by flexing its body. Vernanimalcula means "small spring animal", referring to its appearance in the fossil record at the end of the Marinoan Glaciation (see also Snowball Earth).
The Vernanimalcula fossils were discovered in the Doushantuo Formation in China. This formation is a Lagerstätte, one of the rare places where soft body parts and very fine details are preserved in the fossil record. The Vernanimalcula fossils show triploblastic structure, a coelom, a differentiated gut, a mouth, an anus, and paired external pits that could be sense organs.
The appearance of Vernanimalcula so early in the fossil record has important implications. It greatly reduces the likelihood that animals without coelom (acoelomates), such as flatworms, developed before animals with coeloms. The radiation of animals into many phyla may have occurred before any animal became much larger than microscopic size. The sudden appearance of many animal phyla in the Cambrian Explosion may be an illusion. The Cambrian Explosion may instead represent a (geologically) sudden increase in size and the development of easily fossilized body parts by species in existing phyla.[1][2][3][4]
Criticism
The description of Vernanimalcula was not without controversy. Other workers (Bengtson and Budd) in the field have claimed that it is largely a taphonomic artefact generated by growth of phosphate within a spherical object such as an acritarch.[5] Chen et al. have defended their interpretation of Vernanimalcula against the claims of Bengtson and Budd.[6]
References
- ↑ Chen, J. Y., D. J. Bottjer, P. Oliveri, S. Q. Dornbos, F. Gao, S. Ruffins, H. Chi, C. W. Li, and E. H. Davidson. 2004. Small bilaterian fossils from 40 to 55 million years before the cambrian. Science 305:218-22. (Abstract at [1] - Retrieved June 20, 2007)
- ↑ Supporting Online Material from Science magazine. - accessed October 17 2005
- ↑ Article on Vernanimalcula in Astrobiology Magazine - accessed October 15 2005
- ↑ Article on Vernanimalcula in Scientific American - accessed October 15 2005
- ↑ Bengtson, S.; Budd, G. (2004). "Comment on ‘‘small bilaterian fossils from 40 to 55 million years before the Cambrian.’’". Science 306: 1291a. doi:10.1126/science.1101338. Retrieved on 2007-06-27.
- ↑ Chen, Jun Yuan, Paola Oliveri, Eric Davidson and David J. Bottjer. 2004. Response to Comment on "Small Bilaterian Fossils from 40 to 55 Million Years Before the Cambrian". At [2] - Retrieved June 20, 2007
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
