Fragmentary Dugong or Manatee Rib
cf. Metaxytherium sp. • Body fossil (vertebrate bone fragment)
Geological Period
Neogene (likely Miocene or Pliocene)
Estimated Age
5 to 23 million years ago
Preservation Type
Permineralization with significant water-worn abrasion
Condition Assessment
Poor to Fair; it is a partial fragment lackng diagnostic articulating surfaces or complete anatomy.
Taxonomic Classification
Class: Mammalia; Order: Sirenia; Family: Dugongidae or Trichechidae
Morphological Description
A dense, teardrop-shaped bone fragment exhibiting pachyosteosclerosis (extreme bone density). The surface is heavily weathered and tumbled, showing a dark, mineralized patina with rounded edges and pitting typical of marine erosion.
Rock Matrix
None attached; specimen is isolated and likely recovered from a phosphate-rich marine deposit or beach lag.
Formation & Location
Likely the Peace River Formation or Hawthorne Group in Florida, USA, or similar Neogene coastal deposits in the Atlantic Coastal Plain.
Size & Dimensions
Approximately 2.5 to 3.5 cm in length; very small fragment compared to a full sirenian rib which can exceed 30 cm.
Value & Rarity
Estimated Market Value
$2 - $10 USD
Auction Estimate
$0 - $5 USD (unlikely to be sold as an individual lot)
Rarity Assessment
Common; sirenian rib fragments are frequently found in phosphate mines and river deposits in the Southeast United States.
Scientific Significance
Low; while it confirms the presence of Sirenians in a marine/estuarine environment, the lack of diagnostic features limits its use for specific evolutionary or stratigraphic research.
Preparation Recommendations
No intensive preparation needed. Standard cleaning with water and storage in a dry, stable environment to prevent salt crystallization if found near saltwater.
Notable Features
The most noteworthy feature is the extreme density of the bone (pachyostosis), which is a diagnostic adaptation in sirenians used for ballast while grazing on seagrass.