Xenoturbella is a genus of bilaterian animals; it contains two marine worm-like species. The first known species was discovered in 1915 but was only described in 1949. A 2003 DNA study has shown it is a primitive deuterostome phylum. The genus is now the sole member of its own phylum, the Xenoturbellida.
Xenoturbella has a very simple body plan: it has no brain, no through gut, no excretory system, no organized gonads (but does have gametes), or any other organs except for a statocyst containing flagellated cells. It has cilia and a diffuse nervous system. The animal is up to 4 centimetres (1.6 in) long, and has been found off the coasts of Sweden, Scotland and Iceland.
The association of specimens of Xenoturbella with mollusc larva has led many to suggest that they are molluscivores. However, another idea is that the Xenoturbella larval stage develops as an internal parasite of certain molluscs.
The genus Xenoturbella contains two species:
- Xenoturbella bocki
- Xenoturbella westbladi
- Westblad 1949. Arkiv. Zoologi. 1:3-29
- Bourlat S.J. et al. 2003. Xenoturbella is a deuterostome that eats molluscs. Nature 424 (6951): 925–928 
- G. Haszprunar R.M. & Rieger P. Schuchert 1991. "Extant 'problematica' within or near the Metazoa." In: Simonetta A.M. & Conway Morris S. (eds): The early evolution of metazoa and the significance of problematic taxa. Oxford Univ. Press. 99–105
- Bourlat S.J. et al. 2006. Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida. Nature 444 (7115): 85–88 
- Perseke M. et al. 2007. The mitochondrial DNA of Xenoturbella bocki: genomic architecture and phylogenetic analysis. Theory Biosci. 126(1):35-42. Available on-line at 
- Philippe H. et al. 2011. Acoelomorph flatworms are deuterostomes related to Xenoturbella. Nature 470 (7333): 255-258 
- Enigmatic worm identified as mankind's long lost relative – Accessed January 3, 2008
- Xenoturbella – Back to the basics – Accessed January 3, 2008
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