What is an osteoderm? And what’s it for?
Osteoderm is basically skin and bone (that is the literal Latin meaning). Many species of crocodilians have bony deposits on their dermis – their skin. In crocodiles and other reptiles, these come in the form of scales.
They serve two purposes, in addition to armor.
Firstly, they transfer heat very quickly.
Secondly, they release calcium ions into the bloodstream to combat acidosis. Acidosis is the acidification of blood when too much carbon dioxide accumulates in the bloodstream.
Crocs, of course, spend lots of time underwater and accumulate lots of CO2 when holding their breath.