Subdivision of the lower Palaeozoic articulate brachiopod family Triplesiidae

Reconsideration of the form of the triplesiid pseudodeltidium, which has been used as a basis subdivision into subfamilies, together with the distinct forms of the forked cardinal process, indicates that while these criteria do form useful bases for generic distinction, variation both of combinations of characters an characters within some genera and species mitigate against any meaningful subdivision of this intriguing genetically plastic brachiopod family. A recent proposal to establish families of Triplesiacea based on shell ornamentation is shown to be similarly flawed, and the view is taken that at present the genera are best assig to the single undivided family Triplesiidae.