ABSTRACT
The class Lingulata probably represents a monophyletic group within the phylum Brachiopoda, and is redefined here to include also the orders Paterinida, Acrotretida, and Siphonotretida. The origin of various orders within the group is still not fully explicable, but their morphology is here reviewed, and their Paleozoic, particularly Cambro-Ordovician radiation, evaluated using cladistic analysis.
