Mitrocystites
(drawn by V. Petr)

This beautiful "carpoid" from the Bohemian Ordovician (esp. abundant in the Sarka Formation) is drawn in a position as a "calcichordate" but interpreted as being an echinoderm with typical echinoderm skeleton and having even an aulacophore (bottom), not a "tail".  The "Aulacophore Hypothesis" of Georges Ubaghs and Ronald Parsley is accepted here rather than the "Calcichordate Hypothesis" of R. P. S. Jefferies because it seems that practically all "carpoid" characteristics are clearly echinodermal, not chordate. The superficial similarity may result simply from a peculiar convergent evolution of both groups. An article published recently by Shu et al. (1999) on the discovery of two distinct types of agnathans in the Lower Cambrian of China (Chengjiang) is possibly one of the best arguments for the "Aulacophore Hypothesis".


See esp. the articles:

Parsley, R. (1997): The echinoderm classes Stylophora and Homoiostelea: non Calcichordata, p. 225-248. In: J. A. Waters & Ch. G. Maples (Eds): Geobiology of Echinoderms. - The Paleontological Society Papers, Vol. 3, The Paleontological Society. Pittsburgh (PA).

Ruta, M. (1999): Brief review of the stylophoran debate. - Evolution & Development, 1(2): 123-135. London.

Shu, D. G. - Luo, H. L. - Conway Morris, S. - Zhang, X. L. - Hu, S. X. - Chen, L. Han, J. - Zhu, M. - Li, Y. - Chen, L. Z. (1999): Lower Cambrian vertebrates from south China. - Nature, 402: 42-46. London.

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