Shell microstructure and its inheritance in the calcitic helcionellid Mackinnonia

Mackinnonia davidi from the Cambrian (Series 2) of Australia has a prismatic outer shell layer and, as newly described here, a calcitic semi-nacre inner layer. The pattern is the same as in stenothecids such as Mellopegma, providing more evidence for a strong phylogenetic signal in the shell microst...

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Bibliographic Details
Published in:Estonian journal of earth sciences 2015-03, Vol.64 (1), p.99-104
Main Authors: Vendrasco, Michael J, Checa, Antonio G
Format: Article
Language:English
Subjects:
Analysis
Australia
biomineralization
Cambrian
helcionellid
Mackinnonia
Mollusca
Mollusks
shell microstructure
Structure
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Summary:Mackinnonia davidi from the Cambrian (Series 2) of Australia has a prismatic outer shell layer and, as newly described here, a calcitic semi-nacre inner layer. The pattern is the same as in stenothecids such as Mellopegma, providing more evidence for a strong phylogenetic signal in the shell microstructure of Cambrian molluscs. In addition, calcite now appears to have been common in helcionellids and other molluscs during the early and middle Cambrian, with many species exhibiting foliated calcite. This is surprising given the dominance of aragonite in molluscs, both modern and from post-Cambrian fossil deposits with exceptional shell microstructure preservation, including localities from the Ordovician of the Cincinnati region, USA.
ISSN:1736-4728
1736-7557
DOI:10.3176/earth.2015.18