Spicules or not spicules, that is the question…

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Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium

2014

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Da Silva, A.C., Kershaw, S., Boulvain, F., Hubert, B.L.M., Mistiaen, B., Reynolds, A., Reitner, J.

Lethaia, 47, 365-375, 2014

 

Stromatopres are strange animals that the seabed a long time ago dominated . Etymologically, the term stromatopore literally comes from 'layered' and with holes (pores). The stromatopores were in the Devonian the main reef builders. Just as in the current reefs, where corals can show various shapes, stromatopores can also show flat, rounded or branched morphologies.

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Stromatopores from Tailfer quarry in Lustin, Belgium. Here the stromatoporoids have flat shapes

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These animals were already described in 1826, however a long controversy existed on their taxonomic position, they have been associated with no less than 7 groups of organisms, including bacteria, algae, corals and sponges. They finally, in the 80s, were considered as belonging to the groups of sponges. However, the fact that they do not have spicules unlike the current sponges led some researchers to include them in the group of sponges.

In this work, for the first time, we present a stromatoporoid specimen from Belgium, which dates from about 365 million years ago and shows many structures that we identify as spicules. These spicules definitely allow to fix the stromatoporoides in the group of sponges. In the article, structures are described and compared to today's sponge spicules.
 

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Spicule organisation inside the specimen described in the article.

 

More there: http://www.reflexions.uliege.be/cms/c_41922/en/fossil-sponges?part=

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