and molecular analyses have supported them as among the most basal animals, thus constituting a primitive metazoan phylum.

The first known placozoan, Trichoplax adhaerens, was discovered in 1883 by the German zoologist Franz Eilhard Schulze (1840-1921). Recognizing its distinctive characteristics, the German zoologist Karl Gottlieb Grell (1912-1994) erected a new phylum,