Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Elizabeth Wolfe
Are they brains? Are they ribs? Are they fish helmets? Well the mystery has
These small fossils that resemble brains are actually fish ballast. These fossils are on average about one inch with bilateral symmetry and are quite dense.
You may be wondering just what are fish ballast. Well they are the enlarged spines of fish. Some fish, like sea cows, have enlarged bones to help weigh them down while in the water.
 Fish fossils found in Florida. Retrieved November 9, 2010 from http://www.sharkteethrus.com/fossils/ID-Florida/2fish.htm
 Mayell, Hillary (October 10, 2001). Legged sea cow fossil found in Jamaica. Retrieved November 9, 2010 from National Geographic. http://news.nationalgeographic.com/news/2001/10/1010_jamaicaseacow.html