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Comment
. 2009 Jan 27;7(1):e7.
doi: 10.1371/journal.pbio.1000007.

A new look at some old animals

Neil W Blackstone  1
Affiliations
Comment

A new look at some old animals

Neil W Blackstone. PLoS Biol. .

Abstract

How the tiny marine animalTrichoplax adhaerens is related to other animals has long puzzled researchers studying the origin of metazoans. An ambitious "total evidence" study provides careful analysis of this question and reveals some surprises.

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Figures

Figure 1
Figure 1. Trichoplax adhaerens Individuals Creeping along the Glass Wall of an Aquarium
The nearly “rounded up” individual in the lower center of the image is several millimeters long. Extremely elongate forms such as these are often seen in large aggregations of Trichoplax individuals.
Figure 2
Figure 2. Schemata of Two Hypotheses for the Branching Order of Groups at the Root of the Metazoan Tree
(A) One of several competing hypotheses for early metazoan evolution: the choanoflagellates (which are not animals; see Box 1) serve as an outgroup in the analysis, and sponges are the sister group to the placozoan + cnidarian + ctenophore + bilaterian clade (see [6]). (B) A simplified view of the hypothesis of Schierwater et al. [10]: bilaterians are the sister group to the placozoan + sponge + ctenophore + cnidarian clade, while placozoans are the sister group to the sponge + ctenophore + cnidarian clade. (Artwork courtesy of Austin Parrin)
See this image and copyright information in PMC

Comment on

References

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    1. Syed T, Schierwater B. Trichoplax adhaerens: Discovered as a missing link, forgotten as a hydrozoan, re-discovered as a key to metazoan evolution. Vie Milieu. 2002;52:177–187.

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