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Redescription of the genus Shikamaia, and clarification of the hinge characters of the family Alatoconchidae (Bivalvia)

Published online by Cambridge University Press:  14 July 2015

Thomas E. Yancey  and
Kimihiko Ozaki
Thomas E. Yancey
Affiliation:
Dept. of Geology, Texas A&M University, College Station 77843
Kimihiko Ozaki
Affiliation:
Geological Institute, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama, Japan 240
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Abstract

A new full description of the bivalve Shikamaia akasakaensis Ozaki (genotype species of Shikamaia) is presented, providing the first documentation of its hinge and ligament, and resolving many uncertainties about Shikamaia, the first described genus of the Permian bivalve family Alatoconchidae. The genus Shikamaia has a unique ligament, modified from typical duplivincular ligaments in occupying only half of the cardinal area, and having ligament sheets that extend themselves towards the beak with continued growth. This ligament is strikingly different from the ligaments of other alatoconchid genera. All alatoconchids are believed to have a common ancestry, but the magnitude of difference in their hinges warrants dividing the family into two subfamilies. The subfamily Saikraconchinae is erected new.

Type
Research Article
Information
Journal of Paleontology , Volume 60 , Issue 1 , January 1986 , pp. 116 - 125
Copyright
Copyright © The Journal of Paleontology 

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