7. Boulder Brain Coral

I have two species of coral from my collection that have earned the common name, Brain Corals, due to their convoluted surfaces, loosely resembling the physical brain and general spherical shapes. They are both slow growing, colony forms which may reach colossal sizes to a few meters in length and live for hundreds of years. The oldest know brain coral is 900 years old. Both species below grow in shallow parts of the Caribbean Sea, the Bahamas, Bermuda, Texas and Florida.

Boulder Brain Coral (Colpophyllia, natans) Fossil Skeleton

Boulder Brain Coral (Colpophyllia, natans) is a very large brain coral whose domed, hemispherical colonies may exceed one meter ( 3 feet) across, but smaller colonies may be flat topped discs depending on location. The polyp valleys on the surface may stretch the entire width, or be subdivided into shorter series. The valleys and walls may be two centimeters broad distinguishing it from my Symmetrical Brain Coral (shown below) which have narrower valleys and walls. Also, the walls of the Boulder Brain Coral commonly have a fine grooves running along the tops. There is a sharp break between the wall and the valley floor. The colors vary with ridges being various shades of brown, and the valleys either whitish, green, or tan.

Boulder Brain Coral (Colpophyllia, natans) Living Sample Source

8. Symmetrical Brain Coral

Symmetrical Brain Coral (Diploria, strigosa) Fossil Skeleton

Symmetrical Brain Coral (Diploria, strigosa) forms flat plates or massive hemispherical domes up to 2 meters, (6 feet) in diameters. Sometimes, they will show a very narrow groove along the tops of the walls, which have sloping or rounded sides. Valleys may run straight for considerable distances or be highly irregular in direction. They range in color from purplish brown to grey or green, often with the groove floors being a contrasting paler color. Diploria, strigosa is the most widespread of all the Diploria species, being more resistant to threats with the ability to thrive in muddy stretches of seabed where many other corals are not able to flourish.

Symmetrical Brain Coral (Diploria, strigosa) Source: http://reefguide.org/carib/pixhtml/symmetricalbrain2.html
Symmetrical Brain Coral (Diploria, strigosa) Living Sample

Brain Corals Habitat  Source: http://www.dcbiodata.net/explorer/results/detail/5260
Brain Coral Habitat

NOTE ABOUT SCLERACTINIA: The order, Scleractinia, in which all living corals belong today, means they develop a stony skeleton, which is a light, porous skeleton consisting of external sheathing forming a cup. Scleractinians were fairly rare in North America until the Cretaceous, about 100 million years ago, when they first built reefs in Texas and Mexico. It wasn’t until the Pleistocene Period, about 2.6 million years ago, that reefs flourished where they do today.

Brain Coral Open Polyps At Night
Brain Coral Open Polyps At Night

Night Time Activity : Coral polyps, the living breathing jelly-like part of the animal, are found in single file in the valleys of this brain coral’s convoluted ridges. They are normally contracted during daylight, but expand at night to catch micro-bits of food drifting by.


  • Kingdom  –  Animalia
  • Phylum  –    Cnidaria (means stinging cells)
  • Class  –     Anthozoa (means flower animal)
  • Order  –  Scleratinia (stony skeleton)
  • Family  –  Faviidae (spherical group with grooved surfaces)
  • Genus  –  Diploria /  Colpophyllia
  • Species – strigosa /  natans

Identification and interesting facts about 7 species of Star Corals

© 2022 Kathi Mirto