Discinidae is a family in the

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

superfamily

Discinoidea Discinoidea is a superfamily of Discinid brachiopods. For discussion of Discinid taxonomy, see Discinidae Discinidae is a family in the brachiopod superfamily Discinoidea. Unlike most brachiopods, which have uniformly calcitic or phosphatic ...

. Unlike most brachiopods, which have uniformly calcitic or phosphatic shells, modern-day discinids incorporate tablets of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is o ...

into their valves. These are covered with vesicles into which the siliceous tablets are cemented, much like a closely packed mosaic, and held together with apatite. These vesicles eventually degrade, but nevertheless still leave an imprint on the shell itself. It has been suggested that this siliceous

biomineralisation Biomineralization, also written biomineralisation, is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Such tissues are called mineralized tissues. It is an extremely widespread phenomenon; ...

might also have occurred amongst some of the earliest

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

brachiopods because similar patterns of shell imprints have been observed amongst them too.

References

External links

Brachiopod families Discinida {{brachiopod-stub