The tissue-less (Parazoa), Grant & Todd 1838, are a traditionally used taxon within animals (Animalia), which mainly consists of the sponges (Porifera). In addition to these, only the Placozoa with their only type Trichoplax adhaerens are included. As the name suggests, the common features of the tissue-less are primarily defined negatively: by the lack of specialized nerve or muscle tissue, any organs and basement membranes between connective tissue and epithelium .
Modern, phylogenetic systematics no longer put the two subordinate taxa together.
The following diagram shows a classification according to the conventional system:
- Multicellular animals (Metazoa)
- Rick Hochberg: Evolution and systematics In: Michael Hutchins, Dennis A. Thoney, Neil Schlager (Eds.): Grzimek's Animal Life Encyclopedia - Second Edition - Volume 1 - Lower Metazoans and Lesser Deuterostomes , 2003, pp. 7-14 , ISBN 0787653624