6533b826fe1ef96bd1283b76
RESEARCH PRODUCT
Evolution of Early Metazoa: Phylogenetic Status of the Hexactinellida Within the Phylum of Porifera (Sponges)
J. M. MüllerWerner E. G. MüllerMichael KruseSally P. LeysClaudia Koziolsubject
DeuterostomebiologyCalcareous spongePhylumPhylogeneticsmedia_common.quotation_subjectPolyphylyZoologyProtostomeFlagellatebiology.organism_classificationPhyletic gradualismmedia_commondescription
The evolution of the Metazoa from their protozoan ancestors is one of the greatest puzzles of phylogeny (Willmer 1994; Cavalier-Smith et al. 1996). The emergence of multicellular animals has been explained by two major theories: the syncytial theory (Hadzi 1963) - origin from a multinucleated ciliate - and the colonial theory (Haeckel 1868) - origin from a colonial flagellate - both of which assume a di(poly)phyletic origin of the Metazoa. Numerous attempts to resolve whether the Metazoa are of mono- or polyphyletic origin have sought evidence from a wide variety of developmental and morphological data such as body symmetry, type of development (protostome vs. deuterostome), type of body cavities (coelomates vs. pseudocoelomates), cleavage patterns (determinate vs. indeterminate, spiral vs. radial), origin of photoreceptors, evolution of surface cilitation, etc. (see Morris 1993).
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1998-01-01 |