A systematic revision of the temnospondyl ‘Metoposaurus’ azerouali Dutuit from the Late Triassic of the Argana Basin (Western High Atlas, Morocco) is presented. The type material is redescribed in detail, and a preliminary phylogenetic analysis – the first one dealing with all metoposaurid species – is also conducted in order to test its position within the Metoposauridae. Our analysis places ‘Metoposaurus’ azerouali as sister‐taxon to Arganasaurus lyazidi in a robust clade supported by two unambiguous synapomorphies (bulge‐like tabular horn and exoccipital process visible in dorsal view) and two ambiguous synapomorphies (cultriform process of uniform width and subtriangular posterior Meckelian fenestra). We therefore propose the new combination Arganasaurus azerouali comb. nov. for the species ‘M.’ azerouali. Our analysis also confirms that the central Laurasian genus Metoposaurus is monophyletic but not the genus Koskinonodon, which deserves its own systematic revision. By consequent, the Late Triassic rich vertebrate fauna from the Argana Basin comprises the metoposauroid Almasaurus habazzi, the basal metoposaurid Dutuitosaurus ouazzoui, and the genus Arganasaurus which is represented by the type species A. lyazidi and A. azerouali comb. nov. Combined with the stratigraphical and geographical occurrences of the taxa, our phylogenetic analysis suggests that metoposaurids may have appeared during the Longobardian (late Ladinian) in central Pangea. Their diversification may be linked to the Carnian Pluvial Episode. At least, their extinction may have occurred during the Rhaetian because of the aridification of the climate and/or competition with amniotes. Buffa_et_al_character_taxon_matrixCharacter-taxon matrix of metoposauroidsBuffa_et_al_AppendixS1Appendix S1. Description of characters used in phylogenetic analysis.Buffa_et_al_AppendixS2Appendix S2. Character states for each taxon.Buffa_et_al_AppendixS3Appendix S3. List of nodes returned by phylogenetic analysis with ambiguous and unambiguous synapomorphies.Buffa_et_al_figS1FIG. S1. Character 2: Shape of orbits. All character states are represented.Buffa_et_al_figS2FIG. S2. Character 7: Lacrimal-nasal suture. All character states are represented. Lacrimal in light gray, nasal in dark gray.Buffa_et_al_figS3FIG. S3. Character 8: Lacrimal shape. All character states are represented. Lacrimal in light gray.Buffa_et_al_figS4FIG. S4. Character 13: Postfrontal contribution to orbital margin. All character states are represented. Postfrontal in light gray.Buffa_et_al_figS5FIG. S5. Character 18: Postorbital sulcus-posterior skull margin contact. All character states are represented. Supraorbital canal in light gray, infraorbital and postorbital canal in dark gray.Buffa_et_al_figS6FIG. S6. Character 23: Transverse pterygoid flange. All character states are represented.Buffa_et_al_figS7FIG. S7. Character 24: Palatine ramus medial margin. All character states are represented.Buffa_et_al_figS8FIG. S8. Character 25: Parasphenoid ornamentation. All character states are represented.Buffa_et_al_figS9FIG. S9. Character 30: Orbits in interpterygoid fenestrae. All character states are represented.Buffa_et_al_figS10FIG. S10. Character 38: Paraquadrate accessory foramen. All character states are represented.Buffa_et_al_figS11FIG. S11. Character 40: Foramen magnum shape. All character states are represented.Buffa_et_al_figS12FIG. S12. Character 41: Foramen magnum proportions. All character states are represented.Buffa_et_al_figS13FIG. S13. Character 45: Anterior coronoid tooth row. All character states are represented.Buffa_et_al_figS14FIG. S14. Character 49: Splenial contribution to symphysis. All character states are represented. Splenial in light gray.Buffa_et_al_figS15FIG. S15. Character 50: Posterior Meckelian fenestra shape. All character states are represented.Buffa_et_al_figS16FIG. S16. Character 51: Mandibular anterior ventral margin. All character states are represented.Buffa_et_al_figS17FIG. S17. Character 52: Mandibular tapering in height anteriorly. All character states are represented.