Evolution & Systematics

Figure 5: Phylogenetic tree showing position of Phyla Cnidaria as well as Anthozoans.  Sourced from: Kaloulis, 2000 [http://www.unige.ch/cyberdocuments/theses2001/KaloulisK/these_body.html]

Stony corals (Scleratinia) are the most species rich taxa of all Cnidaria, with over 3600 species. They are generally characterised by their calcium carbonate exoskeleton.

Porites densa is a Scleratinian in the class Anthozoa (see figure 5).  This means that it is a stony coral.  It is suggested that they are closely related to soft corals such as anemones.
Scleratinians have appeared in the fossil record from as early as the mid Triassic (Vollmer & Palumbi, 2002). During this time, the most common coral forms belonged to the Tabulate and Rugose taxa.  Unfortunately both of these groups went extinct toward the end of the Permian (Vollmer & Palumbi).  After this time, Scleratinia experienced adaptive radiation to fill the massive niche space left by the loss of the other coral.