These joints start out calcified, and decalcify as they grow older.
en.wikipedia.org The causative agents include bezoars, foreign bodies, trauma, intestinal worms, lymphadenitis, and, most commonly, calcified fecal deposits known as appendicoliths or fecaliths.
en.wikipedia.org When the worm dies or escapes, the cysts gradually shrink, leaving nodules of fibrous tissues and eggs which can calcify.
en.wikipedia.org Calcium carbonate is vital to calcifying organisms such as shellfish, corals, and coccolithophores (a type of phytoplankton).
en.wikipedia.org Over time, usually more than 30 years, they often become partly calcified.
en.wikipedia.org