Scleralcyonacea


Scleralcyonacea is an order of the class Octocorallia.
It combines the traditional taxa Calcaxonia, Pennatulacea and Helioporacea, as well as a part of Scleraxonia and a part of Stolonifera, and the genera Ideogorgia and Parasphaerasclera. See below for a more detailed description.

History

A clade combining the Calcaxonia, the Pennatulacea and the Helioporacea was identified as early as in a 2006 study and in several later studies; it was usually called informally the Calcaxonia-Pennatulacea clade or the Pennatulacea-Calcaxonia clade.
In 2019, G. C. Williams proposed calling the Calcaxonia-Pennatulacea clade Calcaxonia, but other authors did not adopt this naming proposal.
The phylogenetic study McFadden et al. 2022 assigned the name Scleralcyonacea and the rank of an order to the Calcaxonia-Pennatulacea clade. The study found Octocorallia to be divided into two monophyletic lineages, which the study established as the orders Scleralcyonacea and Malacalcyonacea. Scleralcyonacea was found to contain:
While the genus Isis was historically placed within Calcaxonia as a relative of Keratoisididae and Mopseidae, it was found to be unrelated, with the difference in internode growth patterns being identified as phylogenetically informative.

Name

Scleralcyonacea was named after Greek σκληρός and former coral order Alcyonacea, as most of its members contain either an axial skeleton made of calcium carbonate or sclerites fused with calcitic material.

Taxonomy

Scleralcyonacea contains the monophyletic sea pens as well as 21 other families and two incertae sedis genera. The order includes the following:
Legend : Ca = Calcaxonia, Pe = Pennatulacea, He = Helioporacea, St = Stolonifera, Sc = Scleraxonia, Ho = Holaxonia, Al = Alcyoniina.

Works cited

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