Recently, new genes and their proteins that revealed striking new insights into the early evolution of multicellular animals have been identified and characterized from members of the lowest metazoan phylum, the porifera (sponges). The unexpected result was that the sequences obtained from sponge displayed high similarity to those found in higher metazoa; in consequence, it was concluded that during the transition from protozoa to metazoa the major structural and regulatory proteins evolved only once. The data gathered are now powerful arguments to establish monophyly of metazoa; in addition, new insights on the evolutionary diversification of metazoa were obtained.

The Question of Metazoan Monophyly and the Fossil Record

The Evolution of the Lower Metazoa: Evidence from the Phenotype
Origin and Phylogeny of Metazoans as Reconstructed with rDNA Sequences
Sponges (Porifera) Molecular Model Systems to Study Cellular Differentiation in Metazoa
The Notion of the Cambrian Pananimalia Genome and a Genomic Difference that Separated Vertebrates from Invertebrates
Evolution of Metazoan Collagens
Evolution of Early Metazoa: Phylogenetic Status of the Hexactinellida Within the Phylum of Porifera (Sponges)
Structure and Evolution of Genes Encoding Polyubiquitin in Marine Sponges.