Fossilized Diploria labyrinthiformis Brain Coral
Diploria labyrinthiformis, known by the common name grooved brain coral, is a species of stony coral in the family Faviidae. Found in tropical areas of the west Atlantic Ocean, it has an appearance that makes it familiar to many. This species of reef-building coral has a hemispherical, brain-like shape with a brown, yellow, or gray color. It has characteristic deep, interconnected double-valleys. These polyp-bearing valleys are each separated by grooved ambulacral ridges. There may be a difference in color between the valleys and the grooves. Diploria labyrinthiformis can grow upward at a rate of approximately 3.5 millimeters per year, achieving about 2 meters (6.6 feet) in diameter. During its planktonic larval stage, the coral has locomotion. After that time, it becomes permanently sessile. This species would have lived in the upper Crustaceous Period (late dinosaur era) 65 million to 136 million years ago.
This example was found at the mouth of the Rappahannock River on Mosquito Island, Lancaster County, Virginia and most likely washed ashore coming from Bermuda or Florida. Measurement is 4 ½ inches long by 4 inches wide by 2 ½ inches thick.