Stomozoa
Stomozoa is a taxonomic clade that includes a diverse group of marine animals. It is a major lineage within the Deuterostomia, a superphylum that also includes chordates and echinoderms. Stomozoa comprises two main groups: the Echinodermata (starfish, sea urchins, sea cucumbers) and the Hemichordata (acorn worms and pterobranchs). This clade is defined by a unique shared characteristic, the presence of a stomochord, a hollow, rod-like structure that supports the pharynx. The stomochord is thought to be homologous to the notochord found in chordates.
Characteristics
Stomozoa share a number of distinctive features, including:
- Deuterostome development: During embryonic development, the anus forms first, followed by the mouth.
- Triploblastic: Possessing three germ layers (ectoderm, mesoderm, and endoderm).
- Bilateral symmetry: Having a body plan with two symmetrical halves.
- Coelom: A fluid-filled body cavity.
- Stomochord: A hollow, rod-like structure that supports the pharynx.
Environments
Stomozoa are found in a wide range of marine habitats, from shallow coastal waters to the deep sea. Echinoderms are particularly diverse in coral reefs and other benthic environments. Hemichordates are more commonly found in sediment-rich environments, burrowing into the seabed.
References
Dunn, C. W., Hejnol, A., Matus, D. Q., Pang, K., Browne, W. E., Smith, S. A., ... & Giribet, G. (2014). Broad phylogenetic sampling improves resolution of the animal tree of life. Nature, 505(7483), 493-497.
Bourlat, S. J., Juliusdottir, T., Lowe, C. J., Freeman, R. L., & Arendt, D. (2015). Deuterostome phylogeny revisited: New insights from a mitogenomic analysis of the Xenacoelomorpha. Molecular Biology and Evolution, 32(4), 1011-1021.