Thursday, March 07, 2013

Exquisite Cnidarian Fossils From the Early Cambrian

Embryos, polyps and medusae of the Early Cambrian scyphozoan Olivooides


1. Xi-Ping Dong (a,b)
2. John A. Cunningham (c)
3. Stefan Bengtson (d)
4. Ceri-Wyn Thomas (c)
5. Jianbo Liu (a)
6. Marco Stampanoni (e,f)
7. Philip C. J. Donoghue (c)


a. School of Earth and Space Science, Peking University, Beijing 100871, People's Republic of China

b. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China

c. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK

d. Department of Palaeozoology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, PO Box 50007, Stockholm 104 05, Sweden

e. Swiss Light Source, Paul Scherrer Institut, Villigen 5232, Switzerland

f. Institute for Biomedical Engineering, University of Zürich and ETH Zürich, Rämistrasse, Zürich 8006, Switzerland


The Early Cambrian organism Olivooides is known from both embryonic and post-embryonic stages and, consequently, it has the potential to yield vital insights into developmental evolution at the time that animal body plans were established. However, this potential can only be realized if the phylogenetic relationships of Olivooides can be constrained. The affinities of Olivooides have proved controversial because of the lack of knowledge of the internal anatomy and the limited range of developmental stages known. Here, we describe rare embryonic specimens in which internal anatomical features are preserved. We also present a fuller sequence of fossilized developmental stages of Olivooides, including associated specimens that we interpret as budding ephyrae (juvenile medusae), all of which display a clear pentaradial symmetry. Within the framework of a cnidarian interpretation, the new data serve to pinpoint the phylogenetic position of Olivooides to the scyphozoan stem group. Hypotheses about scalidophoran or echinoderm affinities of Olivooides can be rejected.

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