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1 November 2010 Alphacrinus New Genus and Origin of the Disparid Clade
Thomas E. Guensburg
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Abstract

Alphacrinus mansfieldi new genus and species from the Middle Tremadoc Series (Early Ibexian), near the base of the Ordovician, is the oldest known disparid crinoid. A new family, Alphacrinidae, receives this monospecific genus. Alphacrinus's character mosaic includes primitive traits unknown among other disparids, auguring for disparid origin from a more complexly plated, less standardized antecedent, and echoing the evolutionary progression documented for camerates and cladids. Disparids are diagnosed as those crinoids expressing an arm-like branch from the C ray. Morphologic progression indicates this distinctive trait evolved by modification of CD interray plates, not as an outgrowth from the C ray.

Thomas E. Guensburg "Alphacrinus New Genus and Origin of the Disparid Clade," Journal of Paleontology 84(6), 1209-1216, (1 November 2010). https://doi.org/10.1666/10-030.1
Accepted: 24 June 2010; Published: 1 November 2010
JOURNAL ARTICLE
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KEYWORDS
crinoid
disparid
oldest
Ordovician
Tremadoc
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