Natural calcification of the prosomatic endosternite in the Phalangiidae (Arachnida:Opiliones).

Extracellular masses of crystals are present in the endosternite of certain opilions (Phalangium, Odiellus, and Leiobunum). X-ray spectrography and secondary-ion analysis have shown them to be rich in calcium but poor in phosphorus and other elements. The associated anion has not been identified, but is most probably organic in nature and perhaps an oxalate.