| Porifera | ||
| Porifera | Porifera Home |
| Metazoa | Metazoa | Metazoa | ||||
| Time |
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Metazoa
├─Choanoflagellata
└─Porifera
├─Archaeocyatha
└─┬─Stromatoporoidea
└─┬─Calcarea
└─┬─Hexactinellida
└─┬─Demospongiae
│ ├─Tetractinomorpha
│ └─Ceractinomorpha
└─┬─Homoscleromorpha
└─Eumetazoa
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Organization of the Sponge Sponge Evolution Classification of the Sponges Ecological Role Dendrogram References |
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 2001Sperling 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
