Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia: implications for the ancestral molluscan radula

Smith, Martin R. (2012) Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia: implications for the ancestral molluscan radula. Proceedings of the Royal Society B: Biological Sciences, on-lin. DOI https://doi.org/10.1098/rspb.2012.1577

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Abstract

The Middle Cambrian lophotrochozoans Odontogriphus omalus and Wiwaxia corrugata have been interpreted as stem-group members of either the Mollusca, the Annelida, or a group containing Mollusca + Annelida. The case for each classification rests on the organisms' unusual mouthparts, whose two to three tooth-rows resemble both the molluscan radula and the jaws of certain annelid worms. Despite their potential significance, these mouthparts have not previously been described in detail. This study examined the feeding apparatuses of over 300 specimens from the 505-million-year-old Burgess Shale, many of which were studied for the first time. Rather than denticulate plates, each tooth row comprises a single axial tooth that is flanked on each side by eight to 16 separate shoehorn-shaped teeth. Tooth rows sat on a grooved basal tongue, and two large lobes flanked the apparatus. New observations—the shape, distribution and articulation of the individual teeth, and the mouthparts' mode of growth—are incompatible with an annelid interpretation, instead supporting a classification in Mollusca. The ancestral molluscan radula is best reconstructed as unipartite with a symmetrical medial tooth, and Odontogriphus and Wiwaxia as grazing deposit-feeders.

Item Type:	Article
Uncontrolled Keywords:	IA64;
Subjects:	04 - Palaeobiology
Divisions:	04 - Palaeobiology
Journal or Publication Title:	Proceedings of the Royal Society B: Biological Sciences
Volume:	on-lin
Identification Number:	https://doi.org/10.1098/rspb.2012.1577
Depositing User:	Sarah Humbert
Date Deposited:	24 Aug 2012 15:59
Last Modified:	23 Jul 2013 10:04
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2583

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