Fossil Dugong Rib

Perfectly preserved prehistoric dugong rib from Florida's Oligocene epoch, approximately 30 million years old. The bone is exceptionally solid and dense — a hallmark of dugong ribs known as pachyostosis, an adaptation that helped these ancient marine mammals stay neutrally buoyant while grazing seagrass beds in the warm shallow seas that once covered Florida. Rarely offered in this condition, this is a standout specimen from one of Florida's most productive and oldest marine fossil deposits.

Prehistoric dugongs were once widespread and common in ancient seas, including what is now Florida. Fossil remains of dugongs—especially from the Dugongidae family—have been found in several locations across Florida, dating back to the Miocene and Pliocene epochs (roughly 5 to 20 million years ago). These prehistoric relatives were part of a diverse group of sirenians, which included not only dugongs but also now-extinct sea cows.

Notable fossil locations in Florida:

• Bone Valley Formation (Central Florida): Rich in marine fossils, including dugong ribs and vertebrae.
• Calvert Formation (along the Atlantic coast, extends into other states but has Florida analogs): Known for sirenian fossils.
• Peace River: A popular fossil hunting site where dugong rib fossils (often mistaken for "petrified wood") are commonly found.
• Tampa Bay area: Miocene marine sediments have yielded dugong fossils.
• Florida phosphate mines: Known for exceptional fossil preservation, including dugong material.
• Suwannee Formation (North/Central Florida): An Oligocene-age marine deposit that has yielded well-preserved sirenian material, including dugong bones.

Prehistoric dugong bones, especially the dense, compact ribs (called pachyostotic ribs), are commonly found by fossil hunters in Florida's rivers and quarries. These bones helped the animals stay neutrally buoyant while grazing on seafloor vegetation.