A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale

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Abstract

Odontogriphus omalus was originally described as a problematic non-biomineralized lophophorate organism. Here we re-interpret Odontogriphus based on 189 new specimens including numerous exceptionally well preserved individuals from the Burgess Shale collections of the Royal Ontario Museum. This additional material provides compelling evidence that the feeding apparatus in Odontogriphus is a radula of molluscan architecture comprising two primary bipartite tooth rows attached to a radular membrane and showing replacement by posterior addition. Further characters supporting molluscan affinity include a broad foot bordered by numerous ctenidia located in a mantle groove and a stiffened cuticular dorsum. Odontogriphus has a radula similar to Wiwaxia corrugata but lacks a scleritome. We interpret these animals to be members of an early stem-group mollusc lineage that probably originated in the Neoproterozoic Ediacaran Period, providing support for the retention of a biomat-based grazing community from the late Precambrian Period until at least the Middle Cambrian.

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Figure 1: Odontogriphus omalus from the Middle Cambrian Burgess Shale.
Figure 2: Reconstruction of a colony of Odontogriphus omalus grazing on the cyanobacterium Morania.
Figure 3: Evolutionary tree of the molluscs in the context of the Neoproterozoic–Cambrian substrate revolution35.
Figure 4: Wiwaxia corrugata from the Middle Cambrian Burgess Shale.

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Acknowledgements

We thank S. Bengtson, G. Budd, S. Conway Morris, S. Dornbos, W. Hagadorn, T. Høisaeter and B. Runnegar for reviewing different drafts of this paper. N. Butterfield suggested using the BSE technique and provided unpublished pictures of Wiwaxia. Our research was in part supported by a Post-Doctoral Natural Sciences and Engineering Research Council of Canada grant (to J.-B.C.) and by a Swedish Research Council grant (to C.S.). Permission to collect Burgess Shale specimens was given by Parks Canada to D. Collins. We are thankful to M. Back and J. Waddington from the Royal Ontario Museum for technical help. This is Royal Ontario Museum Burgess Shale Research Project number 6. Author contributions All four authors made significant contributions to this article.

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Correspondence to Jean-Bernard Caron.

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Supplementary information

Supplementary Figure 1

Schematic model of Odontogriphus omalus. (PDF 472 kb)

Supplementary Figure 2

Reconstruction of different preservational modes of the radula of Odontogriphus omalus. (PDF 44 kb)

Supplementary Figure 3

Odontogriphus omalus from the Middle Cambrian Burgess Shale, ROM57718. (PDF 888 kb)

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Caron, J., Scheltema, A., Schander, C. et al. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature 442, 159–163 (2006) doi:10.1038/nature04894

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