Vernanimalcula

Taxobox
fossil_range = Ediacaran


image_caption = The supposed "fossil" of "Vernanimalcula"
regnum = Animalia
subregnum = Bilateria
genus = "Vernanimalcula"

"Vernanimalcula" is a fossil believed by some to represent the earliest known member of the Bilateria (animals with bilateral symmetry). It is known from deposits dating to ma|600|580. The fossils are between 0.1 and 0.2 mm across (roughly the width of one or two human hairs). "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 appear to show triploblastic structure, a coelom, a differentiated gut, a mouth, an anus, and paired external pits that could be sense organs.

The description of "Vernanimalcula" is 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.cite journal
author = Bengtson, S.
coauthors = Budd, G.
year = 2004
title = Comment on ‘‘small bilaterian fossils from 40 to 55 million years before the Cambrian.’’
journal = Science
volume = 306
pages = 1291a
doi = 10.1126/science.1101338
url = http://www.sciencemag.org/cgi/content/full/sci;306/5700/1291a
accessdate = 2007-06-27
pmid = 15550644 ] Chen et al. have defended their interpretation of "Vernanimalcula" against the claims of Bengtson and Budd. [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 [http://www.sciencemag.org/cgi/content/full/sci;306/5700/1291b] - Retrieved June 20, 2007]

The appearance of "Vernanimalcula" so early in the fossil record has important implications. 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. [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 [http://www.sciencemag.org/cgi/content/abstract/1099213v1] - Retrieved June 20, 2007)] [ [http://www.sciencemag.org/cgi/data/1099213/DC1/1 Supporting Online Material from "Science" magazine.] - accessed October 17 2005] [ [http://www.astrobio.net/news/article1005.html| Article on Vernanimalcula in "Astrobiology Magazine"] - accessed October 15 2005] [ [http://www.sciam.com/article.cfm?articleID=000C4E87-7070-10BF-B07083414B7F0000&sc=I100322| Article on Vernanimalcula in "Scientific American"] - accessed October 15 2005]

References