The case of the Carnian (Triassic) conodont genus Metapolygnathus Hayashi

Successive evolutionary trends control the genera Paragondolella Mosher and Metapolygnathus Hayashi over the about 20 Ma long Aegean-Tuvalian timespan. In consideration of their evolutionary criteria, these genera have been retained together with Carnepigondolella Kozur and the two new genera proposed herein, Mazzaella (type species M. carnica ) and Hayashiella (type species H. nodosa ). Mazzaella n. gen. represents a Late Julian side branch of Metapolygnathus , harbouring a platform ornamentation similar to the several million years younger Tuvalian lineage of Carnepigondolella , issued from Hayashiella n. gen. that is intermediary between Metapolygnathus and Carnepigondolella , based on appearance and platform ornamentation.