A classification devised in the 1990s, based on the materials of which the shells are based, united the Craniida and the "articulate" brachiopods in the Calciata, which have calcite shells.
Sebuah klasifikasi dirancang pada 1990-an, berdasarkan bahan dasar cangkang, menyatukan Craniida dan brakiopoda "artikulata" di Calciata, yang memiliki cangkang kalsit.