'Linguliformea' is a subphylum of inarticulate
brachiopods. These were the earliest of brachiopods, ranging from the
Cambrian into the
Holocene. They rapidly diversified during the Cambrian into the
Ordovician, but most families went extinct by the end of the
Devonian.
The articulation in these brachiopods is lacking. These brachiopods have adductor and oblique muscles, but no diductor muscles. The anus is located at the side of the body. The pedicle is a hollow extension of the ventral body wall. Posterior body wall separates dorsal and ventral mantles.
The shells are usually made up of
apatite (calcium phosphate), however rare cases have
calcite or
aragonite shells.