Editing Demosponge (section)

=== Chaetetids ===
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Chaetetids, more formally called "chaetetid hyper-calcified demosponges" (West, 2011), are common calcareous [[fossils]] composed of fused tubules. They were previously classified as extinct [[corals]], [[bryozoans]], [[algae]], [[stromatoporoidea|stromatoporoids]] and [[sclerosponges]]. The chaetetid skeleton has now been shown to be of polyphyletic origin and with little systematic value. Extant chaetetids are also described. This skeleton is now known from three demosponge orders (Hadromerida, Poecilosclerida, and Agelasida). Fossil chaetetid hyper-calcified demosponges can only be classified with information on their spicule forms and the original mineralogy of their skeletons (West, 2011).

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File:Chaetetid Bird Spring Upper Carboniferous Nevada.jpg|Fossil chaetetid from the [[Bird Spring Formation]] ([[Upper Carboniferous]]) of southern [[Nevada]].
File: Chaetetid Bird Spring cross-section Upper Carboniferous Nevada.jpg|Cross-section of a fossil chaetetid (Bird Spring Formation, Upper Carboniferous, Nevada.
</gallery>