Condition in which bones are effected by both Osteosclerosis and Pachyostosis
Pachyosteosclerosis is a combination of thickening (
pachyostosis) and densification (
osteosclerosis) of bones.[1] It makes bones more heavy, but also more fragile. The condition often occurs in aquatic
vertebrates, especially those living in shallow waters,[2] creating
ballast as an adaptation for maintaining neutral
buoyancy and horizontal
trim. It is in no way pathological. To resist
bend, it frequently is found especially in ventral bones, whereas concentration near the lungs helps in maintaining
trim.
Examples of animals showing pachyosteosclerosis are seacows[3] (
dugongs and
manatees), the extinct
Plesiosauria and
Mesosauria[2] and extinct
aquatic sloths.[4]
^Domning, D. P. and V. Debuffrenil (1991). Hydrostasis in the Sirenia - Quantitative Data and Functional Interpretations. Marine Mammal Science 7(4): 331-368.
^
abHoussaye, A. (2009). "Pachyostosis" in aquatic amniotes: a review. Integrative Zoology 4(4): 325-340.
^de Buffrenil, V., A. Canoville, R. D'Anastasio and D. P. Domning (2010). Evolution of Sirenian Pachyosteosclerosis, a Model-case for the Study of Bone Structure in Aquatic Tetrapods. Journal of Mammalian Evolution 17(2): 101-120.
^Amson, E., C. de Muizon, M. Laurin, C. Argot and V. de Buffrenil (2014). Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru. Proceedings of the Royal Society B-Biological Sciences 281.