The Cycliophora are a platyzoan phylum, based on a single genus Symbion. They are so different from other animals that they were put in their own phylum. They were discovered in 1995, and are the most recent new phylum. So far, three species have been found.
- Asexual Feeding Stage – at this stage, the tiny animal is neither male or female. On the posterior end of the sac-like body is a stalk with an adhesive disc, which attaches itself to the host. On the anterior end is a ciliated funnel (mouth) and an anus.
- Sexual Stage – these are even smaller than the feeding stage.
Symbion can reproduce both asexually by budding and sexually. In sexual reproduction the male attaches to a feeding stage and impregnates a budding female. The female then separates from the feeding stage and attaches herself to another host, where the larva in her develops. The female dies, and the larva escapes.
- P. Funch & R.M. Kristensen (1995). "Cycliophora is a new phylum with affinities to Entoprocta and Ectoprocta". Nature. 378 (6558): 711–714. doi:10.1038/378711a0.
- Cycliophora. Answers.com 
- P. Funch, P. Thor & M. Obst (2008). "Symbiotic relations and feeding biology of Symbion pandora (Cycliophora) and Triticella flava (Bryozoa)". Vie et Milieu. 58: 185–188.
- Neves RC, Kristensen RM, Wanninger A (March 2009). "Three-dimensional reconstruction of the musculature of various life cycle stages of the cycliophoran Symbion americanus". J. Morphol. 270 (3): 257–70. doi:10.1002/jmor.10681. PMID 18937332.CS1 maint: multiple names: authors list (link)
- Piper, Ross 2007. Extraordinary animals: an encyclopedia of curious and unusual animals. Greenwood Press.