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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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(p.381) 66 Problematica
Animal Evolution

Claus Nielsen

Oxford University Press

Two of the problematic groups in the animal kingdom in terms of phylogenetic positions are Buddenbrockia (and the Myxozoa as a whole) and Symbion. More recent molecular studies have placed the former in the Cnidaria and the latter in its own phylum, closely related to Entoprocta and Ectoprocta. However, Salvinella and the ‘Mesozoa’ – that is, the parasites Orthonectida and Dicyemida (Rhombozoa) – remain enigmatic, necessitating the addition of a new taxon: Diurodrilus. The Dicyemida and Orthonectida are sometimes placed close to the metazoan stem, and both are even regarded as multicellular organisms or as specialised parasitic flatworms. The two groups may not be sister groups and provide no insights about animal evolution. The dicyemids inhabit the kidneys of cephalopods, while the orthonectids parasitise a variety of marine invertebrates.

Keywords:   evolution, Buddenbrockia, Symbion, Salvinella, Orthonectida, Dicyemida, Diurodrilus, dicyemids, orthonectids, phylogenetic positions

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