Evolution of Scleractinian Corals Inferred from Molecular Systematics

Scleractinian corals have a continuous fossil record from the mid-Triassic, but taxonomic difficulties have impeded an understanding of their evolution. A molecular phylogenetic analysis of mitochondrial 16 S ribosomal RNA showed departures from previous hypotheses of coral evolution. Families clustered into two major groups that do not correspond to morphologically based suborders. These clades differed in their 16 S ribosomal DNA sequence by 29.4 percent, which suggests evolutionary divergence before the appearance of scleractinian skeletons 240 million years ago. Together, these fossil and molecular data suggest multiple origins of the scleractinian skeleton, and the great morphological diversity of present-day scleractinians may be a reflection of these multiple origins.