Sunday, 6 February 2011

Confused by Charniodiscus

Within one of the university draws lie the casts of frondose Ediacaran fossils, famous for changing our understanding of Precambrian life. One such form is Charniodiscus, known for its large frond, prominent stalk and circular holdfast. Until recently I had not taken enough of an interest in either Charnia or Charniodiscus to be able to tell the difference between the two, however, I did recently blog on Charnia and got better acquainted with its morphology. I intend to go back in to the stores and compare the two forms in order to get a better feel for them both (the cast of Charniodiscus can be seen here, with me, in a rather rude pose).

I would also like to be able to compare Charniodiscus to the Cambrian frond Thaumaptilon. The latter had once been linked to Ediacaran frondose fossils, though more specifically Charnia, which has been shown to have grown differently to modern sea pens. Thaumaptilon was perceived as possible evidence that Ediacaran forms had extended into the Phanerozoic and could potentially be linked to Cnidarians. This link does not work with Charnia, however, Charniodiscus resembles Thaumaptilon more closely.  I'm not suggesting that I think they are closely related, just that the resemblance is worth investigating and so far I have done little to no research on this.

My source of confusion, however, is not due to phylogeny. I am open-minded about the phylogenetic position of Charniodiscus, whether it is closely related to Charnia and other rangeomorph Ediacarans, or whether it is some sort of primitive pennatulacean, though I do believe the morphospace data suggests close relationship to Charnia. My source of confusion is this image:

It depicts two types of Charniodiscus, but I have no idea what they are meant to be doing. The website can be seen here, though it is in Japanese and there is no clue as to what is going on or who the picture is by. Are they fighting? Kissing? Accidentally bumping one another? Is this an example of Precambrian violence? or porn? I'm baffled!


Antcliffe, J.B.; Brasier, M.D. (2007a). Charnia and sea pens are poles apart. Journal of Geological Society 164 (1): 49.

Antcliffe, J.B.; Brasier, M.D (2007b). Towards a morphospace for the Ediacara biota. 377–386. In VICKERS-RICH, P. and KOMAROWER, P. (eds). The rise and fall of the Ediacaran biota. Geological Society of London Special Publication 286, London, 456 pp

Shu, D.-G., Conway Morris, S. & Han, J. et al. 2006. Lower Cambrian vendobionts from China and early diploblast evolution. Science, 312, 731–734

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