Coeloscleritophoran

Coeloscleritophora Temporal range: Cambrian-Ordovician
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	incertae sedis
Class:	†Coeloscleritophora
Groups included
	Halkieriids; Chancellorids;

The Coelosclerithophorans are a polyphyletic group of organisms bearing hollow sclerites made of aragonite, and with a supposedly distinctive microstructure.^[1]

Their skeletons may be homologous to those of the molluscs,^[2] and Halkieria looks very much like a polyplacophoran. The shells of this group and the molluscs appear to have originated in the same fashion.^[2] However, there are several reasons to doubt this relationship,^[3] many of which may not pass muster.^[4]

There are two groups within the coeloscleritophorans: the Sachitids, to which Halkieria and Wiwaxia belong, and the Chancellorids. The Ediacaran fossil Ausia has been touted as an ancestral 'intermediate' between both of these groups.^[5]

These are common constituents of Lower Cambrian small shelly fossil assemblages.

References

^ Porter, S. M. (2008). "Skeletal Microstructure Indicates Chancelloriids and Halkieriids Are Closely Related". Palaeontology. 51 (4): 865–879. doi:10.1111/j.1475-4983.2008.00792.x.
^ ^a ^b Bengtson, S. (1992). "The cap-shaped Cambrian fossil Maikhanella and the relationship between coeloscleritophorans and molluscs". Lethaia. 25 (4): 401–420. doi:10.1111/j.1502-3931.1992.tb01644.x.
^ Yochelson, E. L. (1993). "Molluscan affinity of coeloscleritophorans". Lethaia. 26 (1): 47–48. doi:10.1111/j.1502-3931.1993.tb01509.x.
^ Bengtson, S. (1993). "Molluscan affinity of coeloscleritophorans — reply". Lethaia. 26 (1): 48. doi:10.1111/j.1502-3931.1993.tb01510.x.
^ Dzik, Jerzy (August 2009). "Possible Ediacaran Ancestry of the Halkieriids" (PDF). In Smith, Martin R.; O'Brien, Lorna J.; Caron, Jean-Bernard (eds.). Abstract Volume. International Conference on the Cambrian Explosion (Walcott 2009). Toronto, Ontario, Canada: The Burgess Shale Consortium (published 31 July 2009). ISBN 978-0-9812885-1-2.

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[Porter2008-1] Porter, S. M. (2008). "Skeletal Microstructure Indicates Chancelloriids and Halkieriids Are Closely Related". Palaeontology. 51 (4): 865–879. doi:10.1111/j.1475-4983.2008.00792.x.

[Bengtson1992-2] Bengtson, S. (1992). "The cap-shaped Cambrian fossil Maikhanella and the relationship between coeloscleritophorans and molluscs". Lethaia. 25 (4): 401–420. doi:10.1111/j.1502-3931.1992.tb01644.x.

[Yochelson1993-3] Yochelson, E. L. (1993). "Molluscan affinity of coeloscleritophorans". Lethaia. 26 (1): 47–48. doi:10.1111/j.1502-3931.1993.tb01509.x.

[Bengtson1993-4] Bengtson, S. (1993). "Molluscan affinity of coeloscleritophorans — reply". Lethaia. 26 (1): 48. doi:10.1111/j.1502-3931.1993.tb01510.x.

[5] Dzik, Jerzy (August 2009). "Possible Ediacaran Ancestry of the Halkieriids" (PDF). In Smith, Martin R.; O'Brien, Lorna J.; Caron, Jean-Bernard (eds.). Abstract Volume. International Conference on the Cambrian Explosion (Walcott 2009). Toronto, Ontario, Canada: The Burgess Shale Consortium (published 31 July 2009). ISBN 978-0-9812885-1-2.

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