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Animal EvolutionInterrelationships of the Living Phyla$
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Claus Nielsen

Print publication date: 2011

Print ISBN-13: 9780199606023

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199606023.001.0001

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Phylum Calcarea

Phylum Calcarea

(p.27) 7 Phylum Calcarea
Animal Evolution

Claus Nielsen

Oxford University Press

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

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