Demospongea

views updated May 08 2018

Demospongea (Demospongiae; phylum Porifera) A class of sponges that first appears in the Cambrian. The soft tissue of the skeleton is supported by siliceous spicules, each spicule consisting of either a single ray (monaxon) or four rays (tetraxon) diverging at 60° or 120°. Most fossil species are represented by their spicules only, but they can usually be referred to modern families.

A Dictionary of Earth Sciences AILSA ALLABY and MICHAEL ALLABY

Demospongea

views updated May 21 2018

Demospongea See DEMOSPONGIAE.

A Dictionary of Zoology MICHAEL ALLABY

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Demospongea

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