The "traditional" classification was defined in 1869; two further approaches were established in the 1990s: In the "traditional" classification, the Articulata have toothed hinges between the valves, while the hinges of the Inarticulata are held together only by muscles.
Klasifikasi "tradisional" didefinisikan pada tahun 1869; dua pendekatan lebih lanjut didirikan pada 1990-an: Dalam klasifikasi "tradisional", Articulata memiliki engsel bergigi antara katup, sedangkan engsel dari Inarticulata disatukan hanya dengan otot.