Chapter

<i>Phylum</i> Calcarea

Claus Nielsen

in Animal Evolution

Third edition

Published in print December 2011 | ISBN: 9780199606023
Published online December 2013 | e-ISBN: 9780191774706 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199606023.003.0007
Phylum Calcarea

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The Calcarea is a phylum of marine ‘sponges’ consisting of approximately 400 extant species and characterised by calcareous spicules. The fossil record dates back to the Lower Cambrian (Ediacaran). There are two known classes of marine sponges, Calcinea and Calcaronea, which differ both in adult morphology and in embryology. Sponge evolution has been described for decades using the very uncomplicated structure of genera such as Leucosolenia, known as the Ascon type. Evidence from molecular phylogeny and morphological studies revealed that striated roots are present in the larval cilia, supporting the Calcarea’s sister-group relationship with the Eumetazoa (when Homoscleromorpha is excluded in the study) or with the Proepitheliozoa (Homoscleromorpha + Eumetazoa).

Keywords: evolution; Calcarea; marine sponges; Calcinea; Calcaronea; embryology; Leucosolenia; molecular phylogeny; Eumetazoa; Proepitheliozoa

Chapter.  1455 words.  Illustrated.

Subjects: Evolutionary Biology

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