Palaeos:		Porifera
Porifera		Porifera Home

Page Back	Unit Back	Metazoa	Metazoa Dendrogram	Metazoa References	Pieces	Taxon Index
Page Next	Unit Next	Unit Home	Unit Dendrogram	Unit References	Glossary	Time

Porifera - 1

METAZOA  
|--Choanoflagellata
`--PORIFERA
   |--Archaeocyatha  
   `--+--Stromatoporoidea  
      `--+--Calcarea  
         `--+--Hexactinellida  
            `--+--Demospongiae  
               |  |--Tetractinomorpha  
               |  `--Ceractinomorpha  
               `--+--Homoscleromorpha  
                  `--EUMETAZOA

Introduction
Organization of the Sponge
Sponge Evolution
Classification of the Sponges
Ecological Role
Dendrogram
References

Porifera

Tube Sponge; photo from Dive Time

The simplest and perhaps the most ancient of all metazoa, sponges are little more than colonial protozoa (choanoflagellates). At one time classified as "Parazoa" and thought to represent a sterile side-branch on the line of evolutionary ascent to humans and butterflies, molecular phylogeny (e.g. Borchiellini et al 2001 Sperling et al, 2006) now tends to reveal them as a paraphyletic grade of metazoa ancestors (in other words, we all evolved from sponges, or more technically a sponge-like organism, through loss of choanocytes, spicules, and internal water current system. The humble sponge is indeed more surprising than it at first appears. MAK120110

page by MAK120110