Trilobozoa
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Extinct (fossil)
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Trilobozoa ("three-lobed animals") is an extinct phylum of what are presumed to be animals which displayed tri-radial symmetry. Many, if not most, of the better-known trilobozoans lived prior to the Cambrian Explosion, during Ediacaran times.
The most primitive trilobozoans were disk-shaped, typified by Tribrachidium. Through comparisons with the other discoidal trilobozoans, the different "arm" patterns on each genus/species occured due to growth arresting or progressing at different stages of developmental growth.
The more advanced, and much longer-lasting, trilobozoans were cone-shaped, as typified by the long-lived genus Conularia, and had shell-like structures that resemble angular ice-cream cones which may have had three or four corners. The conularids were once thought to be anthozoan cnidarians when they were first discovered. However, the lack of septa or other features diagnostic of anthozoans, along with their triradial symmetry lead some researchers to place the conularids within Trilobozoa. Conularids are not generally thought to be a part of the Vendian fauna, if only because of their fossil record, which begun a little before the Cambrian period, and ended at the close of the Permian.
[edit] References
- Ivantsov, A. Yu., & M. A. Fedonkin. 2002. Conulariid-like fossil from the Vendian of Russia: A metazoan clade across the Proterozoic/Palaeozoic boundary. Palaeontology 45 (6): 1219-1229.
- McMenamin, Mark A. S. The Garden of Ediacara New York: Columbia University Press, 1998. ISBN 0231105592
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