animal skeleton, manatee science
look at those rib bones! they're SO thick. surprisingly, though, their bones aren't very strong - high mineral density is probably why. anyway, the lack of fat is why they can't stand temperatures under ~68 degrees and tend to migrate either south or to hot springs during winter.
some info: (scientific paper) http://etd.fcla.edu/UF/UFE0013069/clifton_k.pdf
(easily-read fact sheet) https://oceantoday.noaa.gov/manatees101/
image sources
skeleton diagram source: https://activerain.com/blogsview/2455870/all-about-manatees
skeleton image: https://www.sciencesource.com/archive/Florida-Manatee-Skeleton-SS2564135.html