Redescription of Arganasaurus (Metoposaurus) azerouali (Dutuit) comb. nov. from the Upper Triassic of the Argana Basin (Morocco), and the first phylogenetic analysis of the Metoposauridae (Amphibia, Temnospondyli)

Abstract

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 analysisthe first one dealing with all metoposaurid speciesis 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.

Cranial morphology of a new phytosaur (Diapsida, Archosauria) from the Upper Triassic of India: implications for phytosaur phylogeny and biostratigraphy

“…The metoposaurid taxa from Morocco belong to the endemic genera Dutuitosaurus and Arganasaurus , whereas Madagascar has yielded poorly preserved or fragmentary indeterminate metoposaurid remains (Buffa et al . 2019; Fortuny et al . 2019).…”

Overview of the Late Triassic (Carnian) actinopterygian fauna from the Argana Basin (Morocco)

“…The age of the different units, with the exception of the T4 member, was estimated from vertebrates and throughout comparison with closely related faunal assemblages. The tetrapod fauna from the T5 member (aetosaurs, metoposaurids, almasaurids, stahleckeriid dicynodonts, rauisuchians and phytosaurs, see Buffa et al, 2019, Butler et al, 2019, Jalil and Peyer, 2007, Khaldoune et al, 2017, Olivier et al, 2019) strongly suggests a Late Triassic (Carnian) age. In particular, this fauna is very close to the Late Triassic assemblages of the North American Chinle Formation and Newark Supergroup, and from Krasiejów and Woźniki, in Poland [Khaldoune et al, 2017].…”

Description of the metoposauridAnaschisma brownifrom the New Oxford Formation of Pennsylvania

“…2); ( 9 ) line drawing of the holotype of Apachesaurus gregorii (UCMP 63845; modified from Spielmann and Lucas, 2012, fig. 10A; right side reflected here); ( 10 ) line drawing of the holotype of Arganasaurus azerouali (MNHN.F.ARG 5; modified from Buffa et al, 2019, fig. 1B); ( 11 ) line drawing of the holotype of Panthasaurus maleriensis (ISI A 56; modified from Chakravorti and Sengupta, 2019, fig.…”

“…Lastly, substantial advancements have been made in metoposaurid paleobiology since the turn of the century. Detailed re-examination of historic specimens to assess cursory or tentative identifications by earlier workers are thus warranted to re-evaluate previous interpretations of alpha taxonomy and spatiotemporal trends within the clade (e.g., Buffa et al, 2019; Chakravorti and Sengupta, 2019; Gee et al, 2020).…”