Dugongid Rib Bone (Sea Cow fossil bone fragment)
cf. Metaxytherium floridanum • Body fossil (vertebrate skeletal element - rib fragment)
Geological Period
Late Miocene to Pliocene
Estimated Age
2 to 10 million years
Preservation Type
Permineralization / Replacement by phosphate and iron minerals
Condition Assessment
Fair; the specimen is incomplete (fragmentary) and shows significant water-wear/abrasion from movement in the Peace River system.
Taxonomic Classification
Phylum: Chordata, Class: Mammalia, Order: Sirenia, Family: Dugongidae, Genus: Metaxytherium or Dioplotherium
Morphological Description
A dense, heavy, and non-porous bone fragment characterized by pachyostosis (thickening of bones). The specimen shows rounded edges due to river tumbling, a dark brown to black coloration consistent with phosphate mineral replacement, and a lack of a visible marrow cavity which is diagnostic for Sirenians.
Rock Matrix
No original matrix remaining; specimen was recovered from loose river gravel associated with the Bone Valley Member and Hawthorn Group.
Formation & Location
Peace River, Arcadia, Florida; Hawthorn Group / Bone Valley Member
Size & Dimensions
Approximately 3-5 inches in length; typical for fragmented mid-section rib bones of Miocene sirenians.
Value & Rarity
Estimated Market Value
5.00 - 15.00 USD
Auction Estimate
10.00 - 20.00 USD (typically sold in bulk lots)
Rarity Assessment
Common; sirenian rib fragments are among the most frequently found vertebrate fossils in the Peace River of Florida.
Scientific Significance
Evidence of coastal Miocene/Pliocene marine ecosystems in Florida. Pachyostotic bones allowed these mammals to act as neutral buoyancy divers, similar to modern manatees and dugongs.
Preparation Recommendations
Clean with a soft brush and water to remove any loose river silt. No stabilization is typically required due to the density of the mineralized bone. Display in a dry environment.
Notable Features
Extreme density (pachyostosis) and dark 'river-patina' coloration. The weight-to-size ratio is the primary indicator of its sirenian origin compared to other mammalian fossils.
Notes
Arcadia Florida peace river