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) Valentin Buffa, Nour-Eddine Jalil, J.-Sébastien Steyer

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Valentin Buffa, Nour-Eddine Jalil, J.-Sébastien Steyer. Redescription of Arganasaurus (Meto- posaurus) azerouali (Dutuit) comb. nov. from the Upper Triassic of the Argana Basin (Morocco), and the first phylogenetic analysis of the Metoposauridae (Amphibia, Temnospondyli). Special pa- pers in palaeontology, Wiley Blackwell Publishing, 2019, 5 (4), pp.699-717. ￿10.1002/spp2.1259￿. ￿hal-02967815￿

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1 2 3 REDESCRIPTION OF ARGANASAURUS (METOPOSAURUS) AZEROUALI (DUTUIT) 4 5 6 COMB. NOV. FROM THE LATE TRIASSIC OF THE ARGANA BASIN (MOROCCO), 7 8 AND THE FIRST PHYLOGENETIC ANALYSIS OF THE METOPOSAURIDAE 9 10 (AMPHIBIA, TEMNOSPONDYLI) 11 12 13 14 15 16 by VALENTIN BUFFA*1, NOUR-EDDINE JALIL1,2 and J.-SEBASTIEN STEYER1 17 18 19 1Centre de Recherche sur la paléobiodiversité et les paléoenvironnements, UMR 7207 CNRS- 20 21 MNHN-UPMC, Muséum national d’Histoire naturelle, CP38, 8 rue Buffon, 75005 Paris ; e- 22 23 24 mails: [email protected], [email protected], jean- 25 26 [email protected] 27 28 29 2BioDEcos Département de géologie, Faculté des Sciences Semlalia, Université Cadi Ayyad, 30 31 Marrakech, Maroc 32 33 34 *Corresponding author 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 Abstract: A systematic revision of the temnospondyl “Metoposaurus” azerouali Dutuit from 4 5 6 the Late Triassic of the Argana Basin (Western High Atlas, Morocco) is presented. The type 7 8 material is redescribed in detail, and a preliminary phylogenetic analysis - the first one dealing 9 10 with all metoposaurid species - is also conducted in order to test its position within the 11 12 Metoposauridae. Our analysis places “Metoposaurus” azerouali as sister-taxon to 13 14 15 Arganasaurus lyazidi in a robust clade supported by two unambiguous synapomorphies 16 17 (buldge-like tabular horn and exoccipital process visible in dorsal view) and two ambiguous 18 19 synapomorphies (cultriform process of uniform width and subtriangular posterior Meckelian 20 21 22 fenestra). We therefore propose the new combination Arganasaurus azerouali comb. nov. for 23 24 the species “M.” azerouali. Our analysis also confirms that the central Laurasian genus 25 26 Metoposaurus is monophyletic but not the genus Koskinonodon which deserves its own 27 28 systematic revision. By consequent, the Late Triassic rich vertebrate fauna from the Argana 29 30 31 Basin comprises the metoposauroid Almasaurus habazzi, the basal metoposaurid Dutuitosaurus 32 33 ouazzoui, and the genus Arganasaurus which is represented by the type species A. lyazidi and 34 35 A. azerouali comb. nov. Combined with the stratigraphic and geographic occurrences of the 36 37 38 taxa, our phylogenetic analysis suggests that metoposaurids may have appeared during the 39 40 Longobardian (late Ladinian) in central Pangea. Their diversification may be linked to the 41 42 Carnian Pluvial Episode. At least, their extinction may have occurred during the Rhaetian 43 44 45 because of the aridification of the climate and/or competition with amniotes. 46 47 48 Keywords: phylogenetic analysis, Metoposauridae, diversification, Carnian Pluvial Episode, 49 50 temnospondyl, Morocco. 51 52 53 54 55 56 The Argana Basin, also called the Argana Corridor (Western High Atlas, Morocco), provides a 57 58 series of continental deposits spanning from the Middle-Late Permian to the early Jurassic. 59 60 Since the 1960s, this basin has yielded numerous fossils that document a key period in the

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1 2 3 evolutionary history of terrestrial vertebrates, including the Permo-Triassic mass extinction 4 5 6 (Khaldoune et al. 2017). 7 8 Among the Triassic amphibians recovered from the Argana Basin, three species of 9 10 11 metoposaurids are known: Dutuitosaurus ouazzoui (Dutuit, 1976), Arganasaurus lyazidi 12 13 (Dutuit, 1976) and “Metoposaurus” azerouali Dutuit, 1976. The latter has been described 14 15 briefly in French by Dutuit (1976, p. 165-176) and its systematic status is controversial as it has 16 17 18 been considered as a nomen dubium by Hunt (1993) but a valid taxon by Schoch and Milner 19 20 (2000). 21 22 23 The family Metoposauridae Watson, 1919 includes temnospondyl amphibians which 24 25 occupied freshwater predatory niches during the Late Triassic, especially between the middle 26 27 28 Carnian and the Norian (Hunt 1993; Schoch and Milner 2000; Sulej 2002; Brusatte et al. 2015). 29 30 Metoposaurids are found in low palaeolatitude deposits in Europe, India, Morocco and North 31 32 America (Case 1922, 1931; Dutuit 1976; Hunt 1993; Sengupta 2002; Sulej 2002; Brusatte et 33 34 al. 2015) and presumably in Algeria, France and Madagascar (Schoch and Milner 2000). The 35 36 37 position of the Metoposauridae within temnospondyls has been an ongoing debate for decades, 38 39 but the current consensus considers them as trematosaurian stereospondyls (Schoch and Milner 40 41 2000; Yates and Warren 2000; Damiani and Yates 2003; Schoch 2008, 2011, 2013). 42 43 44 Several phylogenetic studies involving metoposaurids have been done (Hunt 1993; 45 46 47 Steyer 2002; Ruta et al. 2007; Sulej 2007; Schoch 2008, 2011, 2013; McHugh 2012) but the 48 49 only computer-based phylogenetical analyses to date were conducted on temnospondyls or 50 51 stereospondyls as a whole and did not take into account all metoposaurid species. This study 52 53 provides a systematic revision of the species “Metoposaurus” azerouali Dutuit, 1976 and the 54 55 56 first preliminary phylogenetic analysis of the family Metoposauridae. 57 58 59 60

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1 2 3 Institutional abbreviation. BMNH, British Museum of Natural History, London; MNHN, 4 5 6 Muséum national d’Histoire naturelle, Paris. 7 8 9 10 11 SYSTEMATIC PALAEONTOLOGY 12 13 14 Order TEMNOSPONDYLI Zittel, 1888 15 16 17 Suborder STEREOSPONDYLI Zittel, 1888 18 19 20 Family METOPOSAURIDAE Watson, 1919 21 22 23 Phylogenetic definition. Node-based clade including the last common ancestor of 24 25 26 Dutuitosaurus ouazzoui and Metoposaurus diagnosticus (Meyer, 1842) and all of its 27 28 descendants (see analysis below). 29 30 31 Diagnosis (modified from Sulej 2007). Large oval and widely separated orbits in the anterior 32 33 half of the skull; parasphenoid central depression; broad cultriform process; absence of 34 35 cultriform process keel; quadrate excluded from squamosal by quadratojugal; quadrate condyle 36 37 38 subtriangular in ventral view; paraquadrate foramen present; deep and rounded sinus 39 40 pterygoidei below the oblique crest on the posterior side of the ascending ramus of the 41 42 pterygoid; mandibular dentition strictly on the dentary; prearticular not anteriorly positioned to 43 44 45 the posterior coronoid; articular extending posteriorly between the surangular and the 46 47 prearticular along the dorsal surface of the retroarticular process; parapophysis on two 48 49 neighboring intercentra of presacral and sacral vertebra; neural spine dorsally extended in 50 51 52 posterior trunk or tail; clavicular blade indentation; clavicular contact above the interclavicle; 53 54 unusually large manus and pes; concave anterior margin of the ilium shaft; main axes of the 55 56 proximal and distal heads of the femur set to each other at 90°. 57 58 59 60

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1 2 3 Content. The type species Metoposaurus diagnosticus from Germany; Metoposaurus 4 5 6 krasiejowensis (Sulej, 2002) from Poland (we followed Brusatte et al. 2015 in considering the 7 8 subspecies “M. diagnosticus krasiejowensis” Sulej, 2002 as the species M. krasiejowensis); 9 10 Metoposaurus algarvensis Brusatte, Butler, Mateus and Steyer, 2015 from Portugal; 11 12 Koskinonodon perfectus (Case, 1922) and Koskinonodon bakeri (Case, 1931) (following the 13 14 15 generic attribution of Sulej 2007 and Brusatte et al. 2015) from North America; Koskinonodon 16 17 maleriensis (Chowdhury, 1965) from India (following the generic attribution of Sengupta 2002, 18 19 2003 and the remarks of Brusatte et al. 2015); Dutuitosaurus ouazzoui, Arganasaurus lyazidi 20 21 22 and “Metoposaurus” azerouali from Morocco. 23 24 25 Remarks. In his diagnosis of the Metoposauridae, Sulej (2007) also added large external nostrils 26 27 and an exoccipital-pterygoid suture perpendicular to the skull axis in ventral view. However, 28 29 as these characters are also shared with Callistomordax kugleri Schoch, 2008, sister-taxon to 30 31 the Metoposauridae in our analysis (see below), we consider them as no longer valid for this 32 33 34 diagnosis. 35 36 37 In his revision, Hunt (1993) discriminated the genera Koskinonodon (Case, 1922) and 38 39 Metoposaurus Lydekker, 1890 on the basis of the lacrimal entering or not the orbit 40 41 (respectively). However, as recent works showed that the lacrimal does enter the orbit in the 42 43 44 genus Metoposaurus (Sulej 2002, 2007; Brusatte et al. 2015), this discrimination is no longer 45 46 valid. While the diagnosis of the genus Metoposaurus has been amended (Sulej 2002, 2007; 47 48 Brusatte et al. 2015), Koskinonodon still needs a systematic revision, which is out of the scope 49 50 51 of this paper. 52 53 Apachesaurus gregorii Hunt, 1993 from the Norian of North America has recently been 54 55 56 considered as a juvenile form of a large metoposaurid, potentially Koskinonodon perfectus (Gee 57 58 and Parker 2017, 2018a, b; Gee et al. 2017). To test this hypothesis, we decided to keep the 59 60 species A. gregorii in our phylogenetic analysis.

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1 2 3 Several Metoposaurid taxa from other localities have been erected but they are of 4 5 6 disputed validity: “Metoposaurus santaecrucis” Koken, 1913 from the Triassic of Italy and 7 8 Switzerland has been synonymized with Metoposaurus diagnosticus by Sulej (2002); 9 10 “Metoposaurus heimi” Kuhn, 1932 from southeastern Germany is based on a lost holotype (see 11 12 Schoch and Milner 2000); “Metoposaurus hoffmani” Dutuit, 1978 from the Late Triassic of 13 14 15 Madagascar is not valid according to Hunt (1993) and Schoch and Milner (2000). Fragments 16 17 of presumably metoposaurids have also been mentioned in the lower Keuper and Norian of 18 19 France (Corroy 1928; Cuny and Ramboer 1991) and in the Late Triassic of Algeria (Lehman 20 21 22 1971). 23 24 25 26 27 28 Genus ARGANASAURUS Hunt, 1993 29 30 Type Species. Arganasaurus lyazidi (Dutuit, 1976) 31 32 33 Diagnosis (modified from Hunt 1993). Subtriangular squamosal; shallow otic notch with 34 35 36 buldge-like tabular horn; postero-ventrally angled occipital surface, visible in dorsal view (see 37 38 characters 31 and 35, Buffa et al. 2018, appendix 1). 39 40 41 Content. The type species Arganasaurus lyazidi and Arganasaurus azerouali comb. nov., both 42 43 from the Carnian of the Argana Basin (Locality XIX, and XV and VII bis respectively, upper 44 45 46 part of the “T5 Unit” sensu Dutuit 1976). 47 48 49 Remarks. The diagnosis of the genus Arganasaurus was previously defined by monotypy as 50 51 that of Arganasaurus lyazidi. We add three new diagnostic characters for the genus 52 53 Arganasaurus (see phylogenetic analysis below) and consider the diagnostic characters of Hunt 54 55 (1993) as diagnostic characters of Arganasaurus lyazidi. The first description of the pectoral 56 57 58 girdle elements of the type species Arganasaurus lyazidi (used to code character states for 59 60 characters 61 and 62) is provided on Appendix 1 (Buffa et al. 2018).

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1 2 3 4 5 6 ARGANASAURUS (METOPOSAURUS) AZEROUALI (DUTUIT, 1976) COMB. NOV. 7 8 9 Synonymy. Metoposaurus azerouali Dutuit, 1976 (pl. 35-43; figs 72-77; p. 165-177). 10 11 12 Holotype. MNHN.F.ARG 5, a relatively well preserved and slightly deformed skull (39.5 cm 13 14 long, 35.6 cm wide and 9.1 cm high) described and figured by Dutuit (1976, pl. 35, 36, 41E; 15 16 17 figs 72-74; p. 165, 168, 169, 171, 172, 176). 18 19 20 Paratypes. MNHN.F.ARG 9-1-3: two sub-complete clavicles with the corresponding 21 22 articulated interclavicle described and figured by Dutuit (1976, pl. 41C, p. 172, 173). 23 24 25 Type locality and horizon. Locality XV near the village Imziln, northern part of the Argana 26 27 Basin (Western Atlas, Morocco); Upper section of the “T5 Unit” (sensu Dutuit 1976), Irohalène 28 29 30 Member, Timezgadiouine Formation, Carnian, Late Triassic. 31 32 Referred material. MNHN.F.ARG 1: right clavicle portion; MNHN.F.ARG 2: incomplete 33 34 35 interclavicle; MNHN.F.ARG 3: complete right hemi-mandible; MNHN.F.ARG 4: subcomplete 36 37 left hemi-mandible; MNHN.F.ARG 8: left clavicle with missing ornamentation; 38 39 MNHN.F.AZA 14: interclavicle portion; MNHN.F.AZA 28: subcomplete left clavicle; 40 41 42 MNHN.F.TAL 12: right skull portion; MNHN.F.TAL 16: interclavicle portion; MNHN.F.TAL 43 44 17: left skull portion; MNHN.F.TAL 27: right clavicle portion; MNHN.F.TAL 93: right 45 46 clavicle portion. 47 48 49 Diagnosis (modified from Dutuit 1976; Schoch and Milner 2000). Arganasaurus azerouali 50 51 52 comb. nov. differs from the type species Arganasaurus lyazidi by possessing the following 53 54 autapomorphies (see characters 1, 6, 9, 28, 30 and 50, Buffa et al. 2018, appendix 1): very thick 55 56 and massive cranial and postcranial bones; maxilla entering the orbital margin (shared with 57 58 Dutuitosaurus); lacrimal entering the orbit margin (shared with Metoposaurus and 59 60

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1 2 3 Koskinonodon perfectus); ornamentation with very few ridges; relatively poorly developed 4 5 6 lateral line system (except on the hemi-mandibles); orbits in the anterior quarter of the 7 8 interpterygoid fenestrae (shared with Koskinonodon perfectus); cultriform process very broad 9 10 but narrowing anteriorly; no splenial contribution to the symphysis (shared with 11 12 Dutuitosaurus); subtriangular posterior Meckelian fenestra; very large pitted zone in the 13 14 15 ornamentation of the pectoral girdle elements (shared with Dutuitosaurus ouazzoui, 16 17 Apachesaurus gregorii, Koskinonodon bakeri and Koskinonodon perfectus) . 18 19 20 Remarks. We followed the status of the type material originally given by Dutuit (1976) contra 21 22 Hunt (1993) and Khaldoune et al. (2017) in virtue of the International Code of Zoological 23 24 25 Nomenclature. Hunt (1993) designated the skull MNHN.F.ARG 5 and the articulated clavicles 26 27 and interclavicle MNHN.F.ARG 9-1-3 as lectotype and paralectotypes respectively. Khaldoune 28 29 et al. (2017) later designated the same skull as the lectotype with the hemi-mandibles 30 31 MNHN.F.ARG 3 and MNHN.F.ARG 4 as paralectotypes. However, the skull MNHN.F.ARG 32 33 34 5 and the clavicles and interclavicle MNHN.F.ARG 9-1-3 had already been designated as 35 36 holotype and paratypes respectively by Dutuit (1976) in his original description. No type status 37 38 was given to the hemi-mandibles MNHN.F.ARG 3 and MNHN.F.ARG 4. 39 40 41 Schoch and Milner (2000) considered the large size of A. azerouali comb. nov. as a 42 43 44 diagnostic character. However, as size is subjected to many biases, we follow Hunt (1993) and 45 46 Gee and Parker (2017) for whom it cannot be considered a diagnostic character for 47 48 metoposaurids. Schoch and Milner (2000) also proposed the small teeth in the palatal series of 49 50 51 A. azerouali comb. nov. as a diagnostic character, but we do not consider the teeth of 52 53 MNHN.F.ARG 5 “small” compared to that of other metoposaurids. 54 55 56 57 58 59 REDESCRIPTION 60

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1 2 3 Cranial general features 4 5 6 The holotype MNHN.F.ARG 5 (Fig. 1A) is relatively complete but slightly deformed, 7 8 especially on its palatal surface. The skull is relatively large compared to other metoposaurids, 9 10 11 and the bones are thick (the jugal is 1.0 cm high), rendering the skull massive. 12 13 14 The skull is typically metoposaurian in shape: dorsoventrally compressed, broad 15 16 posteriorly and gradually narrowing anteriorly, and with orbits in anterior position. The nares, 17 18 visible on MNHN.F.TAL 12 and MNHN.F.TAL 17 (Fig. 2), are ovoid and located very 19 20 21 anteriorly. In MNHN.F.ARG 5 (Fig. 1A), they are not visible in dorsal view because they are 22 23 marginal. The orbits are laterally positioned, widely separated and situated in the anterior half 24 25 of the skull. The pineal foramen is situated in the middle of the posterior half of the skull, and 26 27 28 is unusually large (2 cm in diameter). The otic notches are relatively shallow. 29 30 The dermal ornamentation of the cranial bones consists in deep alveoli only, hereby 31 32 33 called ‘pits’ following the usual term for metoposaurids (Hunt 1993; Schoch and Milner 2000; 34 35 Sulej 2002, 2007; Brusatte et al. 2015). The grooves, which indicate an active growth zone 36 37 (Moodie 1908; Dutuit 1976; Steyer 2000; Sulej 2007), are not present here, even between the 38 39 40 nares and the orbits or between the orbits and the pineal foramen as is usually the case in 41 42 metoposaurids (Dutuit 1976; Steyer 2000; Sulej 2007). Most of the cranial sutures are very 43 44 open and well visible. Adding to the unusually large pineal foramen, these characters suggest a 45 46 47 juvenile or a sub-adult growth stage (Boy 1974; Steyer 2000). 48 49 50 51 52 53 Skull Roof 54 55 The premaxilla, incomplete on MNHN.F.TAL 12 and MNHN.F.TAL 17 (Fig. 2), forms 56 57 58 the most anterior part of the skull and contacts the nasal posteromedially, the nares posteriorly 59 60 and the maxilla laterally.

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1 2 3 The nasal is subpolygonal, medially positioned and large, making up most of the skull 4 5 6 width anteriorly. It contacts the premaxilla anteromedially, the frontal posteromedially, the 7 8 prefrontal posterolaterally and the lacrimal and maxilla laterally. 9 10 11 The maxilla is the longest bone on the skull roof and forms the anterolateral margin of 12 13 the skull. It does not bear any ornamentation. It contacts the nasal and premaxilla anteriorly, 14 15 the lacrimal medially and the jugal posteriorly. It also enters the orbit posteromedially (Fig. 16 17 18 1B). The maxilla-jugal suture indeed enters the orbit in its posterior third, which leaves the 19 20 medial third in contact with the maxilla. This is also the case in D. ouazzoui (Dutuit 1976). The 21 22 left maxilla of MNHNF.ARG 5 bears an incomplete row of six teeth on its ventral surface (Fig. 23 24 25 3). 26 27 28 The lacrimal is elongate, almost as long as the preorbital region, contrary to that of M. 29 30 diagosticus, K. perfectus and A. gregorii where it is compact (Schoch and Milner 2000; 31 32 Spielmann and Lucas 2012; Lucas et al. 2016). In A. azerouali comb. nov., it contacts the nasal 33 34 anteromedially, contrary to that of K. perfectus and A. gregorii (Spielmann and Lucas 2012; 35 36 37 Lucas et al. 2016) where this contact is absent. It also contacts the prefrontal medially. On 38 39 MNHN.F.ARG 5, MNHN.F.TAL 12 and MNHN.F.TAL 17, the lacrimal contacts the anterior 40 41 margin of the orbit (Figs 1B, 2). This is also found in Metoposaurus, K. perfectus and K. 42 43 44 maleriensis (Sulej 2007; Brusatte et al. 2015; Lucas et al. 2016). 45 46 47 The prefrontal is large (about half long and third wide of the whole preorbital region) 48 49 and subrectangular. It contacts the nasal anteriorly and the lacrimal anterolaterally (Fig. 1B), 50 51 contrary to that of K. perfectus and A. gregorii where it contacts the nasal and maxilla anteriorly 52 53 (Spielmann and Lucas 2012; Lucas et al. 2016). In A. azerouali comb. nov., it also contacts the 54 55 56 frontal medially and the orbit and postfrontal posteriorly. The prefrontal-postfrontal suture is 57 58 anterolaterally oblique, contrary to M. krasiejowensis (Brusatte et al. 2015), thus the 59 60 contribution of the prefrontal to the orbit is reduced, contrary to K. perfectus and A. gregorii

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1 2 3 (Spielmann and Lucas 2012; Lucas et al. 2016). The prefrontal does not contact the jugal, 4 5 6 contrary to K. bakeri, A. gregorii and A. lyazidi. 7 8 The frontal is subrectangular, elongate (more than the third of the skull length) and 9 10 11 tapered to a point posteriorly. It contacts the nasal anteriorly, the prefrontal anterolaterally, the 12 13 postfrontal posterolaterally and the parietal posteriorly. 14 15 16 The postfrontal is elongate and slightly angled lateromedially, about half the length of 17 18 the postorbital region. It broadly contacts the orbit (Fig. 1B), contrary to K. perfectus and A. 19 20 21 gregorii where this contact is reduced (Spielmann and Lucas 2012; Lucas et al. 2016). It also 22 23 contacts the prefrontal anteriorly, the frontal medially, the postorbital laterally and the 24 25 supratemporal (at least on the right side of MNHN.F.ARG 5) and parietal posteriorly. 26 27 28 The postorbital is elongate, about half the length of the postorbital region. It contacts 29 30 the orbit anteriorly, the postfrontal medially, the jugal laterally, the squamosal posterolaterally 31 32 33 and the supratemporal posteriorly. 34 35 36 The jugal is elongate (more than the half length of the postorbital region) and laterally 37 38 positioned on the skull roof. Its anterior margin is posterior to the anterior orbital margin (Fig. 39 40 1B), contrary to M. diagnosticus, M. krasiejowensis, M. algarvensis and K. maleriensis where 41 42 43 it ends anteriorly to the anterior orbital margin, and to A. gregorii and A. lyazidi where it is 44 45 leveled with the anterior orbital margin. In A. azerouali comb. nov., it forms the anterolateral 46 47 margin of the posterior half of the skull. It borders the orbit anteriorly, and contacts the maxilla 48 49 50 laterally, the postorbital medially and the squamosal posteriorly. 51 52 53 The parietal is subrectangular, tapered to a point anteriorly. It extends from the midline 54 55 of the postorbital-prepineal region to the midline of the postpineal region. It contacts the frontal 56 57 and postfrontal anteriorly, the supratemporal laterally and the postparietal anteriorly. It is 58 59 pierced medially by the pineal foramen in its posterior half. 60

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1 2 3 Sulej (2002) discriminated M. diagnosticus and M. krasiejowensis based on the 4 5 6 prepineal length of the parietal (proportionnally long and short respectively) and the “expansion 7 8 angle” of the parietals (i.e. the angle between the left and right parietal-supratemporal sutures; 9 10 narrow and wide respectively). Brusatte et al. (2015) described M. algarvensis as having a 11 12 prepineal length similar to that of M. krasiejowensis and an expansion angle similar to that of 13 14 15 M. diagnosticus. The expansion angle cannot be measured on the holotype of A. azerouali 16 17 comb. nov. as the left and right parietal-supratemporal sutures are almost parallel. The prepineal 18 19 length is different on the left and right parietals (10.2 cm and 8.6 cm respectively) but both are 20 21 22 similar to the length of M diagnosticus. 23 24 25 The postparietal is small and subrectangular. It contacts the parietal anteriorly, the 26 27 supratemporal anterolaterally and the tabular posterolaterally. Its posterior margin is straight 28 29 medially and concave laterally. It forms the medial part of the posterior margin of the skull 30 31 table. 32 33 34 The supratemporal is subrectangular and elongated (almost the half length of the 35 36 37 postorbital region). It contacts the postfrontal (at least on the right side of MNHN.F.ARG 5) 38 39 and postorbital anteriorly, the parietal medially, the postparietal posteromedially, the squamosal 40 41 laterally and the tabular posteriorly. 42 43 44 The tabular is small and subrectangular. It contacts the postparietal anteromedially and 45 46 47 the supratemporal anterolaterally. Its posterior margin is strongly convex. It forms the 48 49 posterolateral margin of the skull table, and the medial margin of the otic notch. It bears a 50 51 reduced tabular horn compared to other metoposaurids. 52 53 54 The squamosal is subtriangular and pointed anteriorly (Fig. 1B) as in A. lyazidi (it is 55 56 polygonal in the other metoposaurids, Dutuit 1976; Spielmann and Lucas 2012; Lucas et al. 57 58 59 2016). Brusatte et al. (2015) described M. algarvensis as having a subtriangular squamosal but 60

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1 2 3 its medial margin is curved, contrary to the straight medial margin in both Arganasaurus 4 5 6 species. In A. azerouali comb. nov., the squamosal extends on almost two thirds of the 7 8 postorbital length. It contacts the postorbital anteromedially, the jugal anterolaterally, the 9 10 supratemporal medially and the quadratojugal laterally. The posterior margin of the squamosal 11 12 is concave medially and straight laterally. It forms the third quarter of the posterior skull margin 13 14 15 and the anterior and lateral margins of the otic notch. 16 17 18 The quadratojugal is a relatively small, with a length similar to that of the postpineal 19 20 region. Its lateral margin is convex and forms the most posterolateral margin of the skull. It 21 22 contacts the squamosal along the medial margin. 23 24 25 The depth of the otic notches and the development of the tabular horns have been used 26 27 28 to differentiate the Metoposauridae genera (Gregory 1980; Hunt 1993; Schoch and Milner 29 30 2000). Compared with the other metoposaurids, the otic notches of A. azerouali comb. nov. are 31 32 shallow (Figs 1, 4) and their tabular horns are buldge-like and poorly developed (0.9 cm), 33 34 contrary to the posterolaterally projecting tabular horn of other metoposaurids. These otic 35 36 37 notches are similar in shape to that of A. lyazidi. A. gregorii has extremely shallow otic notches 38 39 and no tabular horn – an argument to state that A. gregorii is a juvenile metoposaurid (Gee and 40 41 Parker 2017, 2018a, b; Gee et al. 2017). Here, the otic notches of A. azerouali comb. nov. and 42 43 44 A. lyazidi are not different in relative size (of “intermediate” depth between the well-developed 45 46 otic notches of most metoposaurids and the extremely shallow ones of A. gregorii according to 47 48 Hunt 1993), that is why we consider the shallow otic notches and buldge-like tabular horn of 49 50 51 A. azerouali comb. nov. and A. lyazidi as diagnostic and not related to ontogeny. 52 53 The postorbital canals begin on the posterolateral margin of the squamosal, farther back 54 55 56 than those of D. ouazzoui (Dutuit 1976) but similar to those of K. perfectus (Case 1922; Schoch 57 58 and Milner 2000; Lucas et al. 2016). The canal on the right side of MNHN.F.ARG 5 runs along 59 60 the lateral margin of the squamosal and the left one along the medial margin of the

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1 2 3 quadratojugal. They extend anteriorly on the posterior half of the jugal and form a convex loop 4 5 6 on the posterior half of the postorbital. They end posteriorly on the supratemporal, at the same 7 8 level than the pineal foramen. The width of the postorbital canals progressively increases, from 9 10 0.4 cm on the squamosal to 1.3 cm on the supratemporal. 11 12 13 The infraorbital canal is visible only on MNHN.F.TAL 17 (Fig. 2). It is about 0.7 cm 14 15 wide. It starts on the maxilla, gently curves on the lacrimal between the nare and the orbit, and 16 17 18 continues laterally on the jugal before joining the postorbital canal where the latter forms a 19 20 convex loop. 21 22 23 The supraorbital canal is poorly developed because it forms a punctuated canal rather 24 25 than a continuous groove (Fig. 1). It is about 2 cm wide. It starts on the premaxilla anteriorly 26 27 28 (as seen only on MNHN.F.TAL 12, Fig. 2), curves on the nasal and lacrimal between the nare 29 30 and the orbit (contrary to K perfectus and A. gregorii where it passes medially to the lacrimal, 31 32 Spielmann and Lucas 2012; Lucas et al. 2016), runs medially toward the orbit on the prefrontal, 33 34 frontal, postfrontal and postorbital, where it joins the postorbital canal in its convex loop. 35 36 37 38 39 40 Palate 41 42 43 Dutuit (1976: 169) gave a brief description of the palate. The palate of the holotype is 44 45 46 more deformed and less well-preserved than the skull roof, especially in its anterior portion 47 48 (Fig. 3A). 49 50 51 The interpterygoid fenestrae are extremely large and somewhat teardrop-shaped, with 52 53 an anteriorly tapered end, as in M. algarvensis (Brusatte et al. 2015). They cover most of the 54 55 anterior half of the palatal surface and are separated by a broad cultriform process of the 56 57 58 parasphenoid. The subtemporal fenestrae are large (more than two thirds of the palatal length) 59 60 and subtriangular.

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1 2 3 In palatal view, the orbits are located in a very anterior position within the interpterygoid 4 5 6 fenestrae: they occupy the anteriormost quarter of the latter. This is not the case in other 7 8 metoposaurids (except in K. perfectus, Lucas et al. 2016) in which the orbits are located in the 9 10 second anterior quarter of the interpterygoid fenestrae. These very anterior orbits of A. azerouali 11 12 comb. nov. do not seem linked to a juvenile growth stage because juvenile individuals of D. 13 14 15 ouazzoui have relatively posterior orbits within the interpterygoid fenestrae (Dutuit 1976). 16 17 18 The maxilla bears a row of small teeth (0.4 to 0.5 cm in diameter), of which six are 19 20 visible on MNHN.F.ARG 5 (Fig. 3). A parallel row of teeth (0.2 to 0.8 cm in diameter) extends 21 22 on the palatine and ectopterygoid: eight teeth are visible on the left maxilla and 14 on the right 23 24 25 one, preceded by a large anterior tusk of 1.6 cm wide. No alveoli could be observed, but this 26 27 may be due to the preservation. 28 29 30 The choanae, of approximately 3.6 x 2.2 cm, are relatively large compared with the skull 31 32 size (their maximum length is close to that of the orbit). Both choanae are ovoid-elongate in 33 34 shape, as in M. krasiejowensis, but the right one looks slightly more elongate than the left one 35 36 37 in MNHN.F.ARG 5 (Fig. 3). They are located very posteriorly in comparison with other 38 39 metoposaurids: their posterior border is located at the level of the anterior margin of the 40 41 interpterygoid fenestrae. The inter-choanal distance (of approximately 12 cm) is large, 42 43 44 approximately one third of the maximum skull width, as in M. algarvensis. 45 46 47 The vomerian plateau covers a large part of the anterior palate. Both vomers are partly 48 49 separated by an elongate extension of the cultriform process of the parasphenoid. As the anterior 50 51 portion of the palate is weathered, it is difficult to observe the sutures of the vomer with the 52 53 premaxilla and maxilla. However, the suture of the vomer with the palatine is visible on the 54 55 56 right side of MNHN.F.ARG 5 (Fig. 3): it reaches the posterior tip of the choana. 57 58 59 60

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1 2 3 The palatine is elongate and located just posteriorly to the choana. The left palatine of 4 5 6 MNHN.F.ARG 5 bears a palatal tusk of 1.6 cm in diameter (Fig. 3). Because of its poor 7 8 preservation state, the suture of the palatine with the ectopterygoid is unfortunately not visible. 9 10 11 The parasphenoid has a peculiar shape (Fig. 3): the parasphenoid plate, which forms the 12 13 medial part of the palate posterior to the interpterygoid fenestrae, is very elongate and 14 15 subrectangular. It extends into a very long and wide cultriform process anteriorly, separating 16 17 18 the interpterygoid fenestrae. This cultriform process is tapered to a point anteriorly, also 19 20 separating partly the vomers: its anterior extension is very anteriorly located, at the level of the 21 22 choanae, as is the case in M. krasiejowensis. The dorsal surface (i.e. the surface between the 23 24 25 bone and the skull roof) of the cultriform process forms a gutter in its medial third, as described 26 27 for D. ouazzoui (Dutuit 1976: fig. 4). The posterior quarter of the cultriform process is 28 29 significantly thinner, which differentiates A. azerouali from other metoposaurids and is thus 30 31 considered diagnostic (Case 1922; Dutuit 1976; Hunt 1993; Sengupta 2002; Sulej 2007; 32 33 34 Brusatte et al. 2015; Lucas et al. 2016). The ventral ornamentation of the parasphenoid is 35 36 composed of small subtle pits radiating from the center of the parasphenoid plate to its 37 38 periphery. It extends on the cultriform process on MNHN.F.ARG 5, contrary to all other 39 40 41 metoposaurids except K. perfectus. The T-shaped crista muscularis is visible in the posterior 42 43 half of the parasphenoid plate of MHNH.F.ARG 5 but its medial ridge (i.e. the vertical bar of 44 45 the ‘T’) is damaged (Fig. 3). The horizontal ridges (i.e. the two ridges forming the horizontal 46 47 48 bar of the ‘T’) are around 2.5 cm long each and do not extend on the pterygoid. 49 50 51 The ectopterygoid is located medially to the posterior portion of the maxilla and 52 53 anteriorly to the palatal ramus of the pterygoid. It is elongate and bears a tooth row visible on 54 55 MNHN.F.ARG 5, with the diameter of the tooth basis progressively reducing posteriorly. 56 57 However the ectopterygoid is not a very narrow bone (as seen in M. krasiejowensis): it ends 58 59 60 posteriorly drawing a substantial margin with the subtemporal fenestra, as in M. algarvensis.

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1 2 3 The pterygoid takes most of the posterior half of the palate. It has a typical triradiate 4 5 6 shape in palatal view. Its corpus is subrectangular and contacts the parasphenoid plate in a 7 8 slightly jagged anteroposteriorly oriented margin. The pterygoid-parasphenoid suture is very 9 10 elongate, a typical stereospondyl character (e.g., Yates and Warren 2000). The pterygoid corpus 11 12 extends anterolaterally into the palatal ramus, posterolaterally into the quadrate ramus and 13 14 15 posteromedially into the basipterygoid ramus. The palatine ramus is the longest ramus, 16 17 separating the interpterygoid fenestra and the subtemporal fenestra, and contacting the 18 19 ectopterygoid in its anterior end. The quadrate ramus is very posteriorly widened and forms a 20 21 22 third of the palatal posterior margin. The basipterygoid ramus, visible on the right side of 23 24 MNHN.F.ARG 5, is short. The corpus and palatal rami of the pterygoid are slightly ornamented, 25 26 with small subtle pits. The palatine ramus bears a posterolateral flange, as in most 27 28 metoposaurids. 29 30 31 The quadrate is visible in palatal and occipital view. It consists of a large (proportionally 32 33 34 to the skull size) and bulged bone located at the extremity of the quadrate ramus of the 35 36 pterygoid, posteriorly to the subtemporal fenestra. It is robust and massive, as is the case in M. 37 38 krasiejowensis. Its ventral surface is weathered, especially in its contact zone with the 39 40 41 pterygoid, but an oblique crest is visible. Unfortunately its preservation state does not allow a 42 43 more precise description. 44 45 46 47 48 49 Occiput 50 51 52 The occiput is well preserved, 35.6 cm wide and 9.1 cm high (Fig. 4). These 53 54 measurements are more similar to those of M. krasiejowensis than of M. algarvensis. In A. 55 56 azerouali comb. nov., the dorsal margin of the occiput is slightly convex, as in D. ouazzoui 57 58 59 (Dutuit 1976). The occiput projects posteriorly, similar to all other metoposaurids except A. 60

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1 2 3 gregorii (Hunt 1993; Spielmann and Lucas 2012). The occipital surface is slightly inclined 4 5 6 posteroventrally, making it partially visible in dorsal view, as is the case in A. lyazidi. The 7 8 articular condyles are slightly more ventral than the occipital condyle. 9 10 11 The squamosal is subrectangular and convex in occipital view. It bears the otic notches 12 13 (described above) and the crista falciformis, and contacts the paraquadrate foramen laterally. 14 15 The crista falciformis is present as a modest ridge, as in all metoposaurids. 16 17 18 The pterygoid is the largest bone in occipital view but the less extended posteriorly. Its 19 20 21 ventral margin is relatively straight and makes a third of the occipital width. It borders the 22 23 paraquadrate foramen and bears the otic flange (a posteriorly projecting ridge separating the 24 25 squamosal and the pterygoid on the occipital surface) similar to all metoposaurids. 26 27 28 The exoccipitals form the medial part of the ventral margin of the occiput. They contact 29 30 the foramen magnum dorsally and bear the occipital condyles. These condyles are 3.6 cm wide 31 32 33 and subcircular, as in M. krasiejowensis (those of M. algarvensis look relatively flat but this 34 35 could be due to the preservation state). In A. azerouali comb. nov., these condyles are well- 36 37 spaced along the occipital width (around 3 cm), more than those of D. ouazzoui or M. 38 39 40 krasiejowensis. The ascending branch of the exoccipital forms the occipital pillar (4.3 to 4.9 cm 41 42 high) which bears the posttemporal foramen (see below) and borders the foramen magnum. 43 44 This occipital pillar widens dorsally (around 2.3 cm above the condyles and around 4.8 cm near 45 46 47 the skull dorsal margin). 48 49 50 The foramen magnum is 6.4 cm high and occupies most of the medial margin of the 51 52 occiput (Fig. 4). Its left margin is slightly compressed medially, but the foramen is globally 53 54 keyhole-shaped, similar to all metoposaurids except A. gregorii which has a subtriangular 55 56 foramen magnum (Spielmann and Lucas 2012). In A. azerouali comb. nov., the dorsal portion 57 58 59 of this foramen is relatively high, as in M. algarvensis, but its ventral portion is still deeper. 60

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1 2 3 The paraquadrate foramen is very large and bordered by the squamosal dorsally, the 4 5 6 quadratojugal laterally, the quadrate ventrally and the pterygoid medially (Fig. 4). It is 7 8 subtriangular and very widened transversally (up to 2.7 cm wide), wider than that of D. ouazzoui 9 10 (Dutuit 1976). This differentiates A. azerouali comb. nov. from K. perfectus and A. gregorii 11 12 (Spielmann and Lucas 2012) where the paraquadrate foramen is small. No paraquadrate 13 14 15 accessory foramen has been found on this skull, contrary to M. diagnosticus or A. gregorii 16 17 (Speilmann and Lucas 2012). 18 19 20 The posttemporal foramen is located just above the occipital pillar. It is very small and 21 22 subcircular (1.5 cm in diameter), similar to all metoposaurids except A. gregorii, A. lyazidi, D. 23 24 25 ouazzoui and K. perfectus in which the posttemporal foramen is small and polygonal (Fig. 4). 26 27 28 29 30 Mandible 31 32 33 This study is based on the two associated (but not articulated) hemi-mandibles 34 35 36 (MNHN.F.ARG 3, Fig. 5, MNHN.F.ARG 4, Dutuit 1976, pl. 37C, 38C, 39A, B, E-G) belonging 37 38 to the above-described skull MNHN.F.ARG 5. The right hemi-mandible is complete. As for the 39 40 skull, the impressive dimensions of these hemi-mandibles were also noted by Dutuit (1976: 41 42 43 170). The right hemi-mandible is 46.1 cm long, 6.9 to 2.9 wide (narrowing in the medial third) 44 45 and 8.7 to 2.1 cm high (tapering anteriorly). Both hemi-mandibles mark a convex curve 46 47 anteriorly, terminating in the symphysis. 48 49 50 The dermal ornamentation, visible on the labial side, is almost exclusively composed of 51 52 53 pits, as is the case on the skull roof. The mandibular sensory canals running along the surangular 54 55 and the dentary are deep and well developed (Figs 5A, 5B and see below). This differentiates 56 57 A. azerouali comb. nov. from other metoposaurids. 58 59 60

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1 2 3 The dentary broadens anteriorly and forms the mandibular symphysis which is very long 4 5 6 (4.4 cm), as in most stereospondyls (e.g., Yates and Warren 2000). It contacts the prearticular 7 8 postero-lingually and the surangular postero-labially. Its labial surface is slightly ornamented 9 10 antero-ventrally. It is the only bone bearing large teeth (24 teeth on MNHN.F.ARG 3, between 11 12 29 and 72 mm high) and a symphyseal tusk anteriorly (1.2 cm in diameter and 1.0 cm high on 13 14 15 MNHN.F.ARG 4), as in all metoposaurids. No alveoli could be observed, but this may be due 16 17 to the preservation of the specimen. 18 19 20 The three coronoids are typical of metoposaurids: they bear no dentition, contrary to 21 22 close outgroups such as Callistomordax (Schoch 2008). The anterior coronoid is the shortest 23 24 25 and the posterior one the longest (3.9 and 11.2 cm long respectively). These coronoids contact 26 27 the dentary along their dorsal margins. Ventrally, the anterior coronoid contacts the splenial, 28 29 and the inter- and postero-coronoids contact the postplenial. 30 31 32 The splenials (i.e., splenial sensu stricto and postsplenial) are located anteroventrally 33 34 along the hemi-mandible. They are ornamented with small pits on their labial surface. 35 36 37 The splenial is subrectangular and elongate in lingual view, extending from the middle 38 39 40 of the dentary to the beginning of the convex curve of the mandible. It does not contribute the 41 42 symphysis, contrary to all metoposaurids except D. ouazzoui (Dutuit 1976). 43 44 45 The postsplenial is subtriangular and elongate in lingual view, extending from the 46 47 beginning of the preglenoid region to the middle of the dentary. It is pierced by a small ellipsoid 48 49 50 anterior Meckelian fenestra (1.3 cm long). Dutuit (1976, pl. 75) noticed the presence of three 51 52 splenials on the right hemi-mandible MNHN.F.ARG 3 but only two on the left one 53 54 MNHN.F.ARG 4. As we did not observe any presplenial on all the available hemi-mandibles, 55 56 we do not confirm this asymmetry and think A. azerouali comb. nov. has only two splenials, as 57 58 59 in all temnospondyls (e.g., Jupp and Warren 1986). 60

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1 2 3 The posterior Meckelian fenestra is subtriangular and elongate (Fig. 5D). In contrast, 4 5 6 most metoposaurids show a relatively short fenestra. It is formed by the postsplenial dorsally 7 8 and anteroventrally and the angular ventrally and posteriorly with a weak contribution of the 9 10 prearticular postero-dorsally (as in all metoposaurids, Jupp and Warren 1986). 11 12 13 The Postglenoid Region (PGR) is relatively short (7.0 cm on MNHN.F.ARG 3) and 14 15 composed of the articular dorsally, the surangular labially and the articular and angular 16 17 18 lingually, but not the prearticular (see description below). As noted by Sulej (2007), the PGR 19 20 of metoposaurids does not correspond to the typology given by Jupp and Warren (1986), as it 21 22 bears characters from both “type I” (e.g. prearticular not extending into the PGR) and “type II” 23 24 25 (e.g. angular extending into the PGR). In A. azerouali comb. nov., the PGR bears a strong ridge 26 27 formed by the surangular laterally, and a strong postglenoid process. In lingual view, this 28 29 postglenoid process is slightly higher than the preglenoid process (Fig. 5D). 30 31 32 The prearticular does not extend anteriorly to the anterior border of the adductor fossa, 33 34 as in all metoposaurids (Jupp and Warren 1986). It contacts the postsplenial anteriorly, the 35 36 37 articular posteriorly and the angular ventrally. It bears two dorsal processes on each side of the 38 39 adductor fossa; a small process on the same level as the preglenoid process (see surangular 40 41 below) and the postglenoid process posteriorly, contrary to A. gregorii which does not present 42 43 44 mandibular processes (Spielmann and Lucas 2012). Contrary to M. krasiejowensis, the 45 46 prearticular of A. azerouali comb. nov. does not extend posteriorly into the PGR. 47 48 49 The angular, the most ventral bone posteriorly, is elongate and covers a large surface of 50 51 the hemi-mandible labially. It is subrectangular in lingual view and subtriangular in labial view, 52 53 starting in the PGR, extending to the middle of the dentary and tapering anteriorly. Its labial 54 55 56 surface is very ornamented, bearing numerous pits and small grooves. On its lingual surface, 57 58 the angular contacts the postsplenial anteriorly, the posterior Meckelian fenestra anterodorsally, 59 60

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1 2 3 the prearticular dorsally and the articular posterodorsally. On its labial surface, the angular 4 5 6 contacts the postsplenial anteriorly, the dentary dorsally and the surangular posteriorly. 7 8 The articular is the most posterior bone dorsally. It is mostly visible in lingual view (Fig. 9 10 11 5D) where it is subtriangular and as long as the postglenoid region. It contacts the prearticular 12 13 anteriorly, the angular ventrally and borders the glenoid fossa dorsally. It projects posteriorly 14 15 with the retroarticular process. 16 17 18 The surangular is the most dorsal bone posteriorly in labial view. Visible in labial view 19 20 21 (Fig. 5B), it is very ornamented, with numerous pits. It bears the preglenoid process dorsally 22 23 anterior to the glenoid fossa, contrary to A. gregorii which does not present mandibular 24 25 processes (Spielmann and Lucas 2012). 26 27 28 The mandible bears three lateral line canals: the accessory, superior and inferior 29 30 mandibular canals (Fig. 5B). All canals connect on the posteroventral corner of the surangular. 31 32 33 The accessory mandibular canal is dorsally positioned on the labial surface. It is wide 34 35 36 (width of about 1 cm) but relatively short, and barely extending near the postglenoid region. It 37 38 begins at about a third length of the surangular, marks a convex curve posteroventrally and ends 39 40 on the retroarticular process with all other mandibular canals. 41 42 43 The superior mandibular canal is the longest, almost extending along the whole length 44 45 46 of the labial surface, and narrowing anteriorly (width of 1 cm posteriorly and 0.5 cm anteriorly). 47 48 It runs along the dentary, reaches the most dorsal margin on the angular, and gently decreases 49 50 posteriorly on the surangular, untill the posteroventral corner of this bone where it connects the 51 52 53 other mandibular canals. 54 55 The inferior mandibular canal is ventrally positioned on the labial surface. It is 1 cm 56 57 58 wide but relatively short. It begins ventrally at about half length of the angular, extends on the 59 60

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1 2 3 labial surface, and ends on the posteroventral corner of the surangular where it connects the 4 5 6 other mandibular canals. 7 8 9 10 11 Postcranial elements 12 13 14 We describe here articulated scapular elements and an isolated radius. The scapular 15 16 17 elements, visible on MNHN.F.ARG 9.1-3 (Fig. 6), consist of two sub-complete clavicles and 18 19 their articulated but incomplete interclavicle, designated as paratypes by Dutuit (1976). As for 20 21 the cranial bones, these elements are very thick (about 1 cm). The interclavicle is 24.2 cm long 22 23 24 and 31.5 cm wide; whereas the left and right clavicles are 26.2 and 23.7 cm long and 14.4 and 25 26 15.5 cm wide. These elements are strongly ornamented ventrally: a large region around their 27 28 ossification centers (i.e. the center of the interclavicle and the posterolateral corner of the 29 30 clavicles, Hunt 1993) presents polygonal and large alveoli (i.e ‘pits’), which turn progressively 31 32 33 into deep and elongate grooves radially. 34 35 36 The clavicles are broad and wing-shaped, tapering anteriorly. Their ornamented region 37 38 bearing alveoli occupy around 20% of the left clavicle MNHN.F.ARG 9.2 and 25% of the right 39 40 clavicle MNHN.F.ARG 9.3. Their contact zone with the interclavicle is reduced in ventral view, 41 42 43 and their medial margins are straight. These clavicles differ from those of the European 44 45 Metoposaurus species which bear a proportionally smaller alveolar ornamented region, an 46 47 anterior indentation of their medial margin and a longer contact zone with the interclavicle 48 49 50 (Colbert and Imbrie 1956; Hunt 1993; Long and Murry 1995; Sulej 2002, 2007). The clavicles 51 52 of A. azerouali comb. nov. also bear ventrally a short and curved canal located in their lateral 53 54 corners (Fig. 6). This clavicular canal begins on the posterior part of the lateral margin and ends 55 56 on the anterolateral part of the posterior margin. 57 58 59 60

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1 2 3 The lateral margin of the clavicle is folded vertically and forms a broad dorsal clavicular 4 5 6 process. This process is often broken and thus its orientation varies in the studied specimens: it 7 8 projects medially (e.g. MNHN.F.ARG 9.2, MNHN.F.ARG 8: left clavicle, Dutuit 1976, fig. 76, 9 10 pl. 42B) or laterally (e.g. MNHN.F.ARG 9.3, MNHN.F.ARG 1: right clavicle fragment, Dutuit 11 12 1976, pl. 40B, C). 13 14 15 Ventrally, the interclavicle bears an alveolar ornamented region which is large (around 16 17 18 18% of its total surface), contrary to all Metoposaurus species where it is much smaller. The 19 20 interclavicle of A. azerouali comb. nov. also bears two unornamented processes on which the 21 22 clavicles make contact. It is slightly concave dorsally, gently culminating above its ossification 23 24 25 center. 26 27 28 An isolated radius is preserved on MNHN.F.TAL 12 (Fig. 7): it is 9.51 cm in length, the 29 30 proximal epiphysis is 2.44 cm wide, the distal epiphysis is 1.75 cm wide and the diaphysis is 31 32 1.14 cm in diameter. Relatively elongate with flat surfaces, it is similar to the radius of D. 33 34 ouazzoui (Dutuit 1976). Further preparation is needed before a detailed description of this bone 35 36 37 can be given. 38 39 40 41 42 43 DISCUSSION 44 45 46 Phylogeny 47 48 49 In order to test the systematic position of the species “Metoposaurus” azerouali within 50 51 Metoposauroidea, a phylogenetic analysis was performed. We took into account all currently 52 53 recognized metoposaurid species; i.e., Apachesaurus gregorii (we considered as valid, see 54 55 above), Arganasaurus azerouali comb. nov., Arganasaurus lyazidi, Dutuitosaurus ouazzoui, 56 57 58 Koskinonodon bakeri, Koskinonodon maleriensis, Koskinonodon perfectus, Metoposaurus 59 60 algarvensis, Metoposaurus diagnosticus and Metoposaurus krasiejowensis; and the

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1 2 3 metoposauroids Callistomordax kugleri and Almasaurus habazzi Dutuit, 1972. We also used 4 5 6 the basal stereospondyl Rhineceps nyasaensis (Haughton, 1927) and the basal temnospondyls 7 8 Trimerorachis insignis Cope, 1878 and Eryops megacephalus Cope, 1877 as outgroups. 9 10 11 We built a new matrix of 15 taxa and 63 characters (43 cranial, 9 mandibular, 8 axial 12 13 skeleton and 3 appendicular skeleton, see Buffa et al. 2018, appendix 1, 2) using Mesquite 3.2 14 15 (Maddison and Maddison 2017). We consider this analysis preliminary because our matrix is 16 17 18 based on a modified and synthetic version of the matrices of McHugh (2012), Milner and 19 20 Schoch (2013), Schoch (2013), and Marsicano et al. (2017): we therefore recoded most 21 22 character states (characters 1, 3-6, 9-12, 14, 16, 17, 19-22, 26-29, 31-37, 39, 42, 44, 46-48, 52- 23 24 25 63) but also defined new ones (characters 2, 7, 8, 13, 15, 18, 23-25, 30, 38, 40, 41, 43, 45, 49- 26 27 52) based on direct observations (see Buffa et al. 2018, appendix 1). Our analysis is the first 28 29 computer-based phylogeny of the Metoposauridae because the previous works cited above did 30 31 not consider all the metoposaurid species and the analyses of Hunt (1993) and Sulej (2007) 32 33 34 were not based on computerized parsimony. 35 36 37 Our analysis was performed using PAUP* 4 (Swofford 2003) using heuristic searches 38 39 under the simple stepwise addition sequence and the tree bisection reconnection (TBR) 40 41 algorithm (reconnection limit = 8). Branches with a maximum length of zero were collapsed. 42 43 44 All the character states have the same weight and are considered as non-additive and unordered. 45 46 We obtained three most parsimonious trees with a length of 143 steps, a Consistency Index (CI) 47 48 of 0.5385 and a Retention Index (RI) of 0.6118. Both ACCTRAN and DELTRAN options were 49 50 51 tested to study the optimization of the character states. All synapomorphies found by PAUP*4 52 53 (under both ACCTRAN and DELTRAN options) were studied individually and were 54 55 considered as unambiguous or not, when both options were congruent (see Buffa et al. 2018, 56 57 appendix 3 for the complete list). The strict consensus tree, mapped on the stratigraphical chart 58 59 60 of the middle and Late Triassic, is visible on Figure 8.

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1 2 3 The result is that the species “Metoposaurus” azerouali forms a robust clade with 4 5 6 Arganasaurus lyazidi, supporting its attribution within the genus Arganasaurus and our new 7 8 assignment as Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov. This robust 9 10 Arganasaurus clade (Node G, Fig. 8) is supported by two unambiguous synapomorphies 11 12 (buldge-like tabular horn and exoccipital process visible in dorsal view) and two ambiguous 13 14 15 synapomorphies (cultriform process of uniform width and subtriangular posterior Meckelian 16 17 fenestra). We previously underlined in the description of A. azerouali comb. nov. (see above) 18 19 that these two taxa also shared a subtriangular squamosal, but since this character could be 20 21 22 subjected to individual variation (Spielmann and Lucas 2012), we refrained from using it in our 23 24 phylogenetic analysis. 25 26 27 Our analysis also shows that the species M. diagnosticus from Germany, M. 28 29 krasiejowensis from Poland and M. algarvensis from Portugal form a clade (Node L, Fig. 8) 30 31 supported by three unambiguous synapomorphies (no septomaxilla; prolonged clavicular 32 33 34 contact; reduced pits zone in interclavicle ornamentation) and one ambiguous synapomorphy 35 36 (lacrimal compact). This confirms the hypothesis of Brusatte et al. (2015) for whom 37 38 Metoposaurus is a central Laurasian genus. This Metoposaurus clade shares synapomorphies 39 40 41 with species of Koskinonodon (e.g., Nodes J-K, Fig. 8), which yet appear as stem-taxa of 42 43 Metoposaurus. Indeed, none of the Koskinonodon species form a clade here, which questions 44 45 the monophyly of this genus. This could be linked to the fact that a lacrimal entering the orbit 46 47 48 was considered as diagnostic by Hunt (1993) to define Koskinonodon, although this character 49 50 is also found in the genus Metoposaurus (Sengupta 2002; Sulej 2002, 2007; Brusatte et al. 51 52 2015). 53 54 55 The species “Apachesaurus” gregorii, which was considered here as valid to test its 56 57 position, appears to be sister-taxa to Koskinonodon perfectus (they both form a robust clade 58 59 60 supported by six unambiguous synapomorphies, see Node I, Fig. 8 and Buffa et al. 2018,

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1 2 3 appendix 3): this supports the hypothesis of Gee and Parker (2017, 2018a, b) and Gee et al. 4 5 6 (2017) for whom “Apachesaurus” gregorii may be a juvenile form of a large metoposaurid, 7 8 potentially K. perfectus. 9 10 11 Our results also suggest that Dutuitosaurus ouazzoui is the most basal metoposaurid, as 12 13 considered by Hunt (1993) but contra Schoch and Milner (2000). At least, the robust family 14 15 Metoposauridae (Node E, Fig. 8; see Systematic Palaeontology above for diagnosis and 16 17 18 definition) is comprised, with Almasaurus habazzi and Callistomordax kugleri, in the other 19 20 robust and more inclusive clade Metoposauroidea which is supported by five unambiguous 21 22 synapomorphies and two ambiguous synapomorphies (see Buffa et al. 2018, appendix 3). 23 24 25 26 27 28 Stratigraphic distribution 29 30 31 Before dealing with the evolution of the metoposaurids, a state-of-the-art of their 32 33 stratigraphic distribution has been compiled according to the literature and is visible on Figure 34 35 36 9. It encompasses several stages. Note that the stratigraphic ages of some taxa are not precise 37 38 and the duration of some (sub)stages is debated (see Fig. 9). The temporal limits of the Norian 39 40 indeed vary according to the authors: either 220-208.5 Ma (“short Norian” hypothesis of 41 42 43 Muttoni et al. 2004; Lucas 2018a; Lucas and Tanner 2018) or 227-208.5 Ma (“long Norian” 44 45 hypothesis according to Ogg et al. 2014). To minimize the number of working hypotheses in 46 47 our discussion below, we took into account the longest duration of the Norian (i.e., 227-208.5 48 49 50 Ma). 51 52 53 The metoposauroid Callistomordax comes from the Erfurt Formation in Germany 54 55 (Schoch 2008) dated between 239.5 Ma and 237.5 Ma (Longobardian, late Ladinian, Fig. 9) 56 57 according to the German Stratigraphic Commission (2016). M. diagnosticus is known in the 58 59 Germanic Keuper (Milner and Schoch 2004) with its first occurrence in the Schilfsandstein 60

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1 2 3 (Stuttgart Formation, beginning at 231.5 Ma, late Julian, “middle” Carnian, German 4 5 6 Stratigraphic Commission 2016), and its last occurrence in the Lehrbergschichten (lower Weser 7 8 Formation, last unit of the Carnian, ending at ca. 227 Ma, Cohen et al. 2018). 9 10 11 The Polish Krasiejów bonebed has long been considered late Carnian based on its 12 13 vertebrate assemblage and on a correlation with the German Lehrbergschichten (Dzik 2001, 14 15 2003; Dzik and Sulej 2007; Sulej 2002, 2007). However, recent litho-, bio-, climato- and 16 17 18 chemostratigraphic correlations attribute this bonebed to the Norian, i.e. coeval with the lowest 19 20 strata of the “Middle Grey Sandstones” of the German Arnstadt Formation (= Stubensandstein, 21 22 K5 Unit of the Keuper, Fig. 9, see Milner and Schoch 2004; Szulc 2005, Szulc et al. 2015). In 23 24 25 Germany, M. krasiejowensis is found in the Kielsandstein (upper Weser Formation, Milner and 26 27 Schoch 2004) which is the first unit of the Norian. Note that Milner and Schoch (2004) also 28 29 attributed the German specimen BMNH 37938 from Aixheim to M. krasiejowensis, therefore 30 31 coming to the Middle Stubensandstein, of similar age to the Polish specimens, but Lucas et al. 32 33 34 (2007b) and Lucas (2015) argued against this stratigraphic attribution. The stratigraphic 35 36 distribution of M. krasiejowensis thus extends from the Carnian-Norian boundary (ca. 227 Ma, 37 38 Cohen et al. 2018) to the lower K5 unit of the Keuper (ca. 218.5-209.5 Ma, German 39 40 41 Stratigraphic Commission 2016). 42 43 44 Metoposaurus and the phytosaur Parasuchus have long been used to define the 45 46 Otischalkian and Adamanian Carnian Land Vertebrate Faunachrons (LVF) (e.g. Lucas 1998, 47 48 2010, 2018b; Lucas et al. 2007a, 2012 Lucas and Tanner 2014). Metoposaurus is thus not 49 50 51 thought to extend into the Revuletian, the first and longest LVF of the Norian. However, as just 52 53 shown, Metoposaurus does extend into the Norian both in Germany and Poland (Figs 8, 9), and 54 55 Parasuchus is also present in the Norian Krasiejów bonebed (Dzik and Sulej, 2007; Lucas, 56 57 2018b). This is also the case under the “short Norian” hypothesis, in which the Krasiejów 58 59 60 bonebed is situated at the base of the Norian stage (Szulc et al. 2015).

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1 2 3 Lucas (2018b) partly defined the Otischalkian substage based on the highest occurrence 4 5 6 of the almasaurids. However, as Latiscopus disjunctus Wilson, 1948 is a nomen dubium (Bolt 7 8 and Chatterjee 2000) and the “lettenkeuper almasaurid” of Schoch and Milner (2000) belongs 9 10 to Callistomordax (Schoch, 2008), the family Almasauridae is only known from a single 11 12 locality and horizon in Morocco and cannot be used as index taxa. The LVFs of Lucas (2018b) 13 14 15 are thus questionable (and not used here) because Metoposaurus and Almasaurus cannot be 16 17 considered as indicators of the Carnian. Further studies will test whether the Adamanian LVF 18 19 extends into the Norian (as proposed by Imris et al. 2010, Martz et al. 2013 and Ogg et al. 2014) 20 21 22 or not. Pending these studies, the Otischalkian to Adamanian age of the Indian, North American, 23 24 Moroccan and Portugese metoposaurids given by Lucas (2018b) are not taken into account in 25 26 our discussion below. 27 28 29 The Portuguese M. algarvensis is from the Penina bonebed of the ‘AB2’ Unit of the 30 31 Algarve Basin. This unit is considered as latest Carnian-early Norian in age based on the co- 32 33 34 occurrence of M. algarvensis with a phytosaur indet. (Steyer et al. 2011; Mateus et al. 2014; 35 36 Brusatte et al. 2015) and on biostratigraphic correlations (conchostracans, bivalves, macro- and 37 38 micro-flora) with the Spanish Cofrentes Formation (Arche and López-Gómez 2014). The 39 40 41 Cofrentes Formation lays above strata correlated with the German Schilfsandstein, ending at 42 43 229.5 Ma (Tuvalian, late Carnian, Arche and López-Gómez 2014; German Stratigraphic 44 45 Commission 2016). This will be considered a minimum age for the base of the Portuguese 46 47 48 ‘AB2’ Unit. 49 50 51 The Indian K. maleriensis comes from the Lower Maleri (Pranhita-Godavari Basin) and 52 53 the Tiki formations (Rewa Basin) (Sengupta 2002, 2003). These formations are considered 54 55 coeval based on faunal and floral similarities (Mukherjee et al. 2012, Ray et al. 2016). Both are 56 57 correlated to the lower Ischigualastian fauna of the Ischigualasto Formation on the basis of 58 59 60 faunal resemblance, and are part of the Hyperodapedon Assemblage Zone, commonly used to

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1 2 3 correlate Gondwanan formations (Langer 2005; Bandyopadhay and Sengupta 2006; Ray et al. 4 5 6 2016). The Ischigualasto Formation is bracketed by two volcanic layers, respectively dated 7 8 231.4 ± 0.3 Ma and 225.9 ± 0.9 Ma (late Julian-Tuvalian, late Carnian, Martinez et al. 2011; 9 10 Kent et al. 2014; Langer et al. 2018). In the absence of precise dating for the Indian formations, 11 12 we consider K. maleriensis to be constrained between these brackets (Fig. 9). 13 14 15 The oldest North American metoposaurids (i.e., first occurrence of K. perfectus and 16 17 18 unique occurrence of K. bakeri) come from the Santa Rosa Sandstone and the coeval Camp 19 20 Springs Member of the Dockum Group and Evangeline Member of the Wolfville Formation 21 22 (Long and Murry 1995; Schoch and Milner 2000; Martz et al. 2013; Sues and Olsen 2015). The 23 24 25 Santa Rosa Sandstone is overlain by the Tecovas Member (first occurrence of A. gregorii, K. 26 27 perfectus, Long and Murry 1995; Schoch and Milner 2000), which has been correlated with the 28 29 Blue Mesa and Sonlesa members of the Chinle Formation based on numerous faunal similarities 30 31 (Martz et al. 2013). As a result, the oldest metoposaurid-bearing strata are rough equivalents of 32 33 34 the underlying Shinarump and Mesa Renondo members, the oldest of the Chinle Formation, 35 36 dated between 227 and 225 Ma (Lacian, early Norian, Ramezani et al. 2014). 37 38 39 The highest occurrences of metoposaurids in North America come from the upper part 40 41 of the Petrified Forest Member of the Chinle Formation (A. gregorii, K. perfectus) and the upper 42 43 44 Redonda Formation of the Dockum Group (A. gregorii, Hunt 1993; Long and Murry 1995; 45 46 Schoch and Milner 2000; Spielmann and Lucas 2012). The Petrified member specimens come 47 48 from under the Black Forest Bed, dated just under 210 Ma, in the latest Norian (Ramezani et 49 50 51 al. 2014; Gee and Parker 2018a). We consider this age as minimum for the Redonda Formation, 52 53 which is stratigraphically higher than the Petrified Forest Member (Fig. 9, Martz et al. 2013). 54 55 56 The Moroccan metoposaurids all come from the Irohalène Member (“T5” unit sensu 57 58 Dutuit, 1976, Timezgadiouine Formation) of the Argana Basin. This unit has traditionally been 59 60 considered of Carnian age based on its faunal assemblage (Khaldoune et al. 2017). The

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1 2 3 underlying Aglégal Member (“T4” unit sensu Dutuit 1976) has been dated as Middle Triassic 4 5 6 (Anisian-Ladianian) based on charophytes, ostracods and vertebrate remains (Medina et al. 7 8 2001; Jalil et al. 2009, Khaldoune et al. 2017). Microfloral remains have suggested a late 9 10 Carnian-earliest Norian age for the overlying Tadrarat Ouadou Member (“T6” unit sensu Dutuit 11 12 1976, Bigoudine Formation; Tourani et al. 2000; Khaldoune et al. 2017). As there is no 13 14 15 apparent discontinuity between the T4 and T5 units, the T5 unit may comprise the early Carnian 16 17 and at least part of the late Carnian. However we cannot attribute more precise ages for these 18 19 “lower” and “upper” horizons of Dutuit (1976) (Fig. 9). 20 21 22 23 24 25 Evolution of the Metoposauridae 26 27 28 According to the phylogeny obtained and the stratigraphic and geographic distributions 29 30 of the considered taxa (Figs 8, 9), we can propose evolutionary scenarios for the metoposaurid 31 32 33 origin, diversification and extinction: 34 35 36 As Callistomordax kugleri from the Longobardian (upper Ladinian) of Germany 37 38 (Schoch 2008) is the oldest known metoposauroid (Fig. 8), the ages of divergence of both the 39 40 clade (Callistomordax + Metoposauridae) and the Metoposauridae may be Longobardian or 41 42 43 older. Since Almasaurus (sister-taxon to the clade Callsitomordax + Metoposauridae) and 44 45 Dutuitosaurus (basal metoposaurid) are Moroccan, these divergences may have occurred in 46 47 central Pangea, around southern Laurasia or northern Gondwana. 48 49 50 The German M. diagnosticus and the Indian K. maleriensis are the oldest metoposaurids 51 52 53 whose first occurrences are well constrained (ca. 231.5-231 Ma, late Julian-early Tuvalian, 54 55 “middle” Carnian, Fig. 8). Their almost simultaneous appearance in Laurasian and Gondwanan 56 57 formations suggest a rapid diversification of the Metoposauridae. Their first occurrence is 58 59 coeval with the Carnian Pluvial Episode (CPE; Simms and Ruffell 1989; Ruffell et al. 2016), a 60

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1 2 3 global climate change in the late Julian (“middle” Carnian, 1.2 Ma long and ending at ca. 231 4 5 6 Ma according to Dal Corso et al. 2018) during which the climate turned from arid to humid and 7 8 then to arid again (Figs 8, 9). As metoposaurids occupied freshwater environments (Hunt 1993; 9 10 Schoch and Milner 2000; Brusatte et al. 2015), they may have benefited from an increasing 11 12 number of large freshwater areas during that time. As argued by Fortuny et al. (2017), the large- 13 14 15 sized metoposaurid species indeed thrived in large freshwater bodies. The CPE could therefore 16 17 have favored the metoposaurid diversification, as it was also proposed for the dinosaur radiation 18 19 (Bernardi et al. 2018), but further studies will test this hypothesis. In particular, a more precise 20 21 22 dating of the Moroccan metoposaurid bonebeds is needed before a strong correlation between 23 24 the CPE and the metoposaurid diversification can be made. 25 26 27 As the earliest diverging taxa (D. ouazzoui, A. lyazidi and A. azerouali) are Moroccan, 28 29 this diversification of the Metoposauridae may have occurred in northern Gondwana first, then 30 31 in western Laurasia (neighbor province near the palaeoequator in the Late Triassic, Brusatte et 32 33 34 al., fig. 13), then in eastern Gondwana (India, K. maleriensis) and eastern Laurasia 35 36 (Metoposaurus). 37 38 39 To explain the occurrence of K. maleriensis in higher palaeolatitudes in the late Carnian 40 41 of India, Sengupta (2002, 2003) proposed that metoposaurids could have used circum-tethyan 42 43 44 shoreline connections. This possible circum-tethyan dispersion is also supported by the fact that 45 46 all the metoposaurid localities were in a summerwet climatic biozone according to the model 47 48 of Selwood and Valdes (2006, see also Brusatte et al. 2015). However, the current metoposaurid 49 50 51 fossil record is still too sparse to support a robust scenario explaining their dispersion. 52 53 In the Norian (following the commonly accepted “long Norian” hypothesis, Muttoni et 54 55 56 al. 2004; Ogg et al. 2014; Cohen et al. 2018), metoposaurids appear to be mostly located in 57 58 Laurasia, with only K. maleriensis potentially extending in Gondwana (India) during the earliest 59 60 Norian (Figs 8, 9). Fortuny et al. (2017) proposed that the aridification of the climate during

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1 2 3 the Norian may have led to the decline of metoposaurids. These authors argued that the group 4 5 6 underwent a trend in size diminution during the Norian, as diminutive taxa such as A. gregorii 7 8 would have been better suited to arid climates, which is why they are more represented in these 9 10 horizons. This trend in size diminution has been refuted by Gee and Paker (2017, 2018a) on the 11 12 basis of A. gregorii being a juvenile metoposaurid, and evidence shows that the metoposaurids 13 14 15 could withstand some variety of climates (Konietzko-meier and Klein 2013). However, 16 17 metoposaurids are indeed rarer in the higher Norian horizons. In addition, it has been proposed 18 19 that in nonmarine environments, the unspecialized metoposaurids may have faced difficulties 20 21 22 competing with more specialized taxa, especially suction feeders such as the piscivorous 23 24 phytosaurs (Schoch and Milner 2000) and the brachyopoids and plagiosaurids (whom vaulted 25 26 palate is specialized in suction feeding, see Warren et al. 2000; Sengupta 2003). Further studies 27 28 are needed to test this hypothesis. Following their decline during the Norian, metoposaurids are 29 30 31 only represented by isolated material non-diagnostic beyond the family level in the Rhaetian of 32 33 North America (Spielmann et al. 2007). 34 35 36 37 38 39 CONCLUSION 40 41 42 43 44 45 The systematic revision and detailed redescription of “Metoposaurus” azerouali Dutuit, 46 47 1976 from the Late Triassic of Morocco have highlighted its close relationship with 48 49 50 Arganasaurus lyazidi and led to the new combination Arganasaurus (Metoposaurus) azerouali 51 52 (Dutuit, 1976) comb. nov., proposed here. Its comparison with other metoposaurids led to the 53 54 first phylogeny of the Metoposauridae, which confirms that the genus Metoposaurus is 55 56 composed of central Laurasian species and supports the hypothesis that “Apachesaurus” 57 58 59 gregorii may be a juvenile form of Koskinonodon perfectus known in the Norian of North 60

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1 2 3 America. The current fossil record of the Metoposauroidea together with the phylogeny 4 5 6 obtained suggest that the group diverged at least during the Longobardian (late Ladinian), and 7 8 diversified around the late Julian (“middle” Carnian). This diversification could be linked to 9 10 the Carnian Pluvial Episode (CPE), a global climate change from arid to humid conditions 11 12 coeval with the first strongly constrained occurrences of metoposaurids. Metoposaurids may 13 14 15 have diversified first in northern Gondwana and then in western Laurasia, southern Gondwana 16 17 and central Laurasia, in tropical humid biomes. Their decline may be linked to the aridification 18 19 of the climate in the Norian and competition with other more specialized taxa, leading to their 20 21 22 extinction in the Rhaetian in North America. 23 24 25 26 27 28 Acknowledgements. We thank V. Barriel (MNHN) for her phylogenetic help to V.B., P. Loubry 29 30 (CNRS Paris) for the photos of the studied specimens, D. Germain (MNHN), G. Clément 31 32 (MNHN) and S. Crasquin (CNRS) for their authorization to study the material. We thank C. 33 34 Marsicano and two anonymous reviewers for their constructive reviews, and S. Thomas and K. 35 36 37 Angielczyk for their editorial works. 38 39 40 41 42 43 DATA ARCHIVING STATEMENT 44 45 46 Data for this study are available in the Dryad Digital Repository: 47 48 https://datadryad.org/review?doi=doi:10.5061/dryad.d6s5h2d [please note that the data for 49 50 this paper are not yet published and this temporary link should not be shared without the 51 52 53 express permission of the author] 54 55 File 1. Character-taxon matrix. 56 57 58 59 60

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1 2 3 SUPPORTING INFORMATION 4 5 6 Additional Supporting Information can be found in the online version of this article 7 8 9 Appendix S1. Description of characters used in phylogenetic analysis. 10 11 12 Appendix S2. Character states for each taxon. 13 14 15 Appendix S3. List of nodes returned by phylogenetic analysis with ambiguous and 16 17 unambiguous synapomorphies. 18 19 20 FIG. S1. Character 2: Shape of orbits. All character states are represented. 21 22 23 FIG. S2. Character 7: Lacrimal-nasal suture. All character states are represented. Lacrimal in 24 25 26 light gray, nasal in dark gray. 27 28 29 FIG. S3. Character 8: Lacrimal shape. All character states are represented. Lacrimal in light 30 31 gray. 32 33 34 FIG. S4. Character 13: Postfrontal contribution to orbital margin. All character states are 35 36 represented. Postfrontal in light gray. 37 38 39 FIG. S5. Character 18: Postorbital sulcus-posterior skull margin contact. All character states 40 41 are represented. Supraorbital canal in light gray, infraorbital and postorbital canal in dark 42 43 44 gray. 45 46 47 FIG. S6. Character 23: Transverse pterygoid flange. All character states are represented. 48 49 50 FIG. S7. Character 24: Palatine ramus medial margin. All character states are represented. 51 52 53 FIG. S8. Character 25: Parasphenoid ornamentation. All character states are represented. 54 55 56 FIG. S9. Character 30: Orbits in interpterygoid fenestrae. All character states are represented. 57 58 59 FIG. S10. Character 38: Paraquadrate accessory foramen. All character states are represented. 60

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1 2 3 FIG. S11. Character 40: Foramen magnum shape. All character states are represented. 4 5 6 FIG. S12. Character 41: Foramen magnum proportions. All character states are represented. 7 8 9 FIG. S13. Character 45: Anterior coronoid tooth row. All character states are represented. 10 11 12 FIG. S14. Character 49: Splenial contribution to symphysis. All character states are 13 14 represented. Splenial in light gray. 15 16 17 FIG. S15. Character 50: Posterior Meckelian fenestra shape. All character states are 18 19 20 represented. 21 22 23 FIG. S16. Character 51: Mandibular anterior ventral margin. All character states are 24 25 represented. 26 27 28 FIG. S17. Character 52: Mandibular tapering in height anteriorly. All character states are 29 30 represented. 31 32 33 34 35 36 REFERENCES 37 38 39 ARCHE, A. and LÓPEZ-GÓMEZ, J. 2014. The Carnian Pluvial Event in Western Europe: new 40 41 data from Iberia and correlation with the Western Neotethys and Eastern North 42 43 44 America–NW Africa regions. Earth-Science Reviews, 128, 196–231. 45 46 47 BANDYOPADHYAY, S. and SENGUPTA, D. P. 2006. Vertebrate faunal turnover during the 48 49 Triassic-Jurassic transition: an Indian scenario. New Mexico Museum of Natural History 50 51 and Science Bulletin, 37, 77–85. 52 53 54 BERNARDI, M., GIANOLLA, P., PETTI, F. M., MIETTO, P. and BENTON, M. J. 2018. 55 56 57 Dinosaur diversification linked with the Carnian Pluvial Episode. Nature 58 59 Communications, 9, 1–10. 60

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1 2 3 BOLT, J. R. and CHATTERJEE, S. 2000. A new temnospondyl amphibian from the Late 4 5 6 Triassic of Texas. Journal of Paleontology, 74 (4), 670–683. 7 8 BOY, J. A. 1974. Die Larven der rhachitomen Amphibien (Amphibia: Temnospondyli; 9 10 11 Karbon-Trias). Paläontologische Zeitschrift, 48, 236–268. 12 13 14 BRUSATTE, S. L., BUTLER, R. J., MATHEUS, O. and STEYER, J.-S. 2015. A new species 15 16 of Metoposaurus from the Late Triassic of Portugal and comments on the systematics 17 18 and biogeography of metoposaurid temnospondyls. Journal of Vertebrate Paleontology, 19 20 21 35 (3), 1–23. 22 23 24 BUFFA, V., JALIL, N. –E, STEYER, J. –S. 2018. Data from : Redescription of Arganasaurus 25 26 (Metoposaurus) azerouali (Dutuit) comb. nov. from the Late Triassic of the Argana 27 28 Basin (Morocco), and the First Phylogenetic Analysis of the Metoposauridae 29 30 (Amphibia, Temnospondyli). Dryad Digital Repository. 31 32 33 https://doi.org/10.5061/dryad.d6s5h2d 34 35 36 CASE, E. C. 1922. New reptiles and stegocephalians from the Upper Triassic of western Texas. 37 38 Carnegie Institution of Washington, 321, 7–84. 39 40 41 — 1931. Description of a new species of Buettneria with a discussion of the brain case. 42 43 Contributions from the Museum of Paleontology, University of Michigan, 3, 187–206. 44 45 46 CHOWDHURY, T. R. 1965. A new metoposaurid amphibian from the upper Triassic Maleri 47 48 49 Formation of Central India. Philosophical Transaction of the Royal Society of London, 50 51 Series B, 250, 1–52. 52 53 54 COHEN, K. M., FINNEY, S. C., GIBBARD, P. L. and FAN, J.-X. 2018 (2013; updated). The 55 56 ICS International Chronostratigraphic Chart. Episodes 36, 199–204. 57 58 59 60

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1 2 3 COLBERT, E. H. and IMBRIE, J. 1956. Triassic metoposaurid amphibians. Bulletin of the 4 5 6 American Museum of Natural History, 110, 402–452. 7 8 COPE, E. D. 1877. Description of extinct Vertebrate from the Permian and Triassic formations 9 10 11 of the United States. Proceedings of the American Philosophical Society, 17, 182–193. 12 13 14 — 1878. Description of extinct Batrachia and Reptilia from the Permian Formation of Texas. 15 16 Proceedings of the American Philosophical Society, 17, 505–530. 17 18 19 CORROY, G. 1928. Les vertébrés du Trias de Lorraine et le Trias Lorrain. Annales de 20 21 Paléontologie, 17, 83–136. 22 23 24 CUNY, G. and RAMBOER, G. 1991. Nouvelles données sur la faune et l’âge de Saint Nicholas 25 26 27 de Port. Revue de Paléontologie, 10, 69–78. 28 29 30 DAL CORSO, J., BENTON, M. J., BERNARDI, M., FRANZ, M., GIANOLLA, P., HOHN, 31 32 S., KUSTATSCHER, E., MERICO, A., ROGHI, G., RUFFELL, A., Ogg, J. G, PRETO, 33 34 N. SCHMIDT, A. R., SEYFULLAH, L. J., SIMMS, M. J., SHI, Z. and ZHANG, Y. 35 36 2018. First workshop on the Carnian Pluvial Episode (Late Triassic): a 37 38 39 report. Albertiana, 44, 49–57. 40 41 42 DAMIANI, R. J. and YATES, A. M. 2003. The Triassic amphibian Thoosuchus yakovlevi and 43 44 the relationships of the Trematosauroidea. Records of the Australian Museum, 55, 331– 45 46 342. 47 48 49 DUTUIT, J. M. 1972. Un nouveau genre de stégocéphale du Trias supérieur marocain : 50 51 52 Almasaurus habbazi. Bulletin du Muséum National d’Histoire Naturelle, Série C, 53 54 Sciences de la Terre, 72, 73–81. 55 56 57 — 1976. Introduction à l’étude paléontologique du Trias continental marocain : Description 58 59 des premiers Stégocéphales recueillis dans le couloir d’Argana (Atlas occidental). 60

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1 2 3 4 5 6 FIGURE CAPTIONS 7 8 9 FIG. 1. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 10 11 Triassic of the Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in dorsal view. A, 12 13 14 photograph; B, interpretive drawing. Scale bars represent 10 cm. Anatomical abbreviations: Fr, 15 16 frontal; Ju, jugal; La, lacrimal; Mx, maxilla; Na, nasal; Orb, orbit; Pa, parietal; Pfr, postfrontal; 17 18 Pif, pineal foramen; Po, postorbital; Po.c, postorbital canal; Ppa, postparietal; Prf, prefrontal; 19 20 21 Qj, quadratojugal; So.c, supraorbital canal; Sq, squamosal; Su, supratemporal; Tab, tabular. 22 23 24 FIG. 2. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 25 26 Triassic of the Argana Basin, Morocco: MNHN.F.TAL 12 and MNHN.F.TAL 17 skull 27 28 fragments. A, MNHN.F.TAL 12 in dorsal view; B, MNHN.F.TAL 12 in ventral view; C, 29 30 MNHN.F.TAL 17 in dorsal view. Scale bars represent 10 cm. 31 32 33 FIG. 3. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 34 35 36 Triassic of the Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in ventral view. A, 37 38 photograph; B, interpretive drawing. Scale bars represent 10 cm. Anatomical abbreviations: 39 40 Ch, choana; Cr.ms, crista muscularis; Cu.pr, cultriform process of the parasphenoid; Ect, 41 42 43 ectopterygoid; Exo, exoccipital; If, interpterygoid fenestra; Orb, orbit; Pal, palatine; Pal.t, 44 45 palatal tusk; Ps, parasphenoid; Pt, pterygoid; Q, quadrate; Stf, subtemporal fenestra; Vo, vomer. 46 47 48 FIG. 4. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 49 50 Triassic of the Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in occipital view. A, 51 52 53 photograph; B, interpretive drawing. Scale bars represent 10 cm. Anatomical abbreviations: 54 55 Cr.fal, crista falciformis; Exo, exoccipital; Fm, foramen magnum; Oc, occipital condyle; Of, 56 57 otic flange; On, otic notch; Ppa, postparietal; Pq.f, paraquadrate foramen; Pt, pterygoid; Pt.f, 58 59 posttemporal foramen; Q, quadrate; Qj, quadratojugal; Sq, squamosal; Tab, tabular. 60

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1 2 3 FIG. 5. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 4 5 6 Triassic of the Argana Basin, Morocco: MNHN.F.ARG 3. Complete right hemi-mandible in 7 8 labial view, A, photograph; B, interpretive drawing; and lingual view, C, photograph; D, 9 10 interpretive drawing. Scale bars represent 10 cm. Anatomical abbreviations: Am.c, accessory 11 12 mandibular canal; aMf, anterior Meckelian fenestra; Ang, angular; Art, articular; Co1, anterior 13 14 15 coronoid; Co2, intercoronoid; Co3, posterior coronoid; De, dentary; Glf, glenoid fossa; Im.c, 16 17 inferior mandibular canal; Par, prearticular; poGl.Pr, postglenoid process; pMf, posterior 18 19 Mekelian fenestra; poSp, postsplenial; prGl.Pr, preglenoid process; Rart.Pr, retroarticular 20 21 22 process; Sang, surangular; Sm.c, superior mandibular canal; Sp, splenial; Sy, symphysis. 23 24 25 FIG. 6. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 26 27 Triassic of the Argana Basin, Morocco: MNHN.F.ARG9-1-3, paratype, articulated clavicles 28 29 MNHN.F.ARG 9.1 and MNHN.F.ARG 9.2 and interclavicle MNHN.F.ARG 9.3 in ventral 30 31 view. A, photograph; B, interpretive drawing. Scale bars represent 15 cm. Anatomical 32 33 34 abbreviations: Cl, clavicle; Cl.c, clavicular canal; Ic, interclavicle. 35 36 37 FIG. 7. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late 38 39 Triassic of the Argana Basin, Morocco: MNHN.F.TAL 12, isolated radius encased in the 40 41 ventral surface of the skull fragment. Anatomical abbreviations: Orb, orbit; Ra, radius. 42 43 44 FIG. 8. Phylogeny of the Metoposauroidea and position of Arganasaurus (Metoposaurus) 45 46 47 azerouali (Dutuit, 1976) comb. nov.. Strict consensus of three most parsimonious trees (L=143; 48 49 CI = 0.5385; RI = 0.6118, see text) mapped on the stratigraphic chart of the Middle and Late 50 51 Triassic (stratigraphic chart after Cohen et al. 2018). Node labels: Node letter/Bremer support 52 53 value (when above 1). Black bars indicate the unambiguous stratigraphic distribution of the 54 55 56 taxa and dotted lines indicate the range of uncertainty of this distribution. CPE scale bar 57 58 represents the duration of the Carnian Pluvial Episode (dated according to Dal Corso et al. 59 60

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1 2 3 2018). Abbreviations: Myr, million years. Carn., Carnian; Hett., Hettangian; Ladin., Ladinian; 4 5 6 Rhaet., Rhaetian; Sinem., Sinemurian. 7 8 FIG. 9. Correlation chart of all the Late Triassic metoposauroid-bearing formations across 9 10 11 Pangaea. Stratigraphic chart after Cohen et al. (2018), uncertainty on the duration of the Norian 12 13 stage collowing Ogg et al. (2014), Land Vertebrate Faunachrons (LVF) according to Lucas 14 15 (2018b) and Carnian Pluvial Episode (CPE, in blue) dated according to Dal Corso et al. (2018). 16 17 18 Dotted lines indicate an uncertain age and arrows indicate the extent of this uncertainty. 19 20 Abbreviations: Adam., Adamanian; Alaun., Alaunian; Apach., Apachean; Berdyan., 21 22 Berdyankian; Fass., Fassanian; Fm., Formation; Longob., Longobardian; Mb., Member; 23 24 25 Otisch., Otischalkian; Perov., Perovkan; Revuel., Revueltian; Sevat., Sevatian; Tuval., 26 27 Tuvalian; Wass., Wassonian. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

51 Palaeontology Palaeontology Page 52 of 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 FIG. 1. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in dorsal view. A, photograph; B, interpretive 25 drawing. Scale bars represent 10 cm. Anatomical abbreviations: Fr, frontal; Ju, jugal; La, lacrimal; Mx, 26 maxilla; Na, nasal; Orb, orbit; Pa, parietal; Pfr, postfrontal; Pif, pineal foramen; Po, postorbital; Po.c, 27 postorbital canal; Ppa, postparietal; Prf, prefrontal; Qj, quadratojugal; So.c, supraorbital canal; Sq, 28 squamosal; Su, supratemporal; Tab, tabular. 29 30 165x86mm (300 x 300 DPI) 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Page 53 of 60 Palaeontology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 FIG. 2. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the 26 Argana Basin, Morocco: MNHN.F.TAL 12 and MNHN.F.TAL 17 skull fragments. A, MNHN.F.TAL 12 in dorsal 27 view; B, MNHN.F.TAL 12 in ventral view; C, MNHN.F.TAL 17 in dorsal view. Scale bars represent 10 cm. 28 29 165x94mm (300 x 300 DPI) 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Palaeontology Page 54 of 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 FIG. 3. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the 24 Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in ventral view. A, photograph; B, interpretive 25 drawing. Scale bars represent 10 cm. Anatomical abbreviations: Ch, choana; Cr.ms, crista muscularis; 26 Cu.pr, cultriform process of the parasphenoid; Ect, ectopterygoid; Exo, exoccipital; If, interpterygoid fenestra; Orb, orbit; Pal, palatine; Pal.t, palatal tusk; Ps, parasphenoid; Pt, pterygoid; Q, quadrate; Stf, 27 subtemporal fenestra; Vo, vomer. 28 29 166x83mm (300 x 300 DPI) 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Page 55 of 60 Palaeontology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 FIG. 4. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the 32 Argana Basin, Morocco: MNHN.F.ARG 5, holotype skull in occipital view. A, photograph; B, interpretive 33 drawing. Scale bars represent 10 cm. Anatomical abbreviations: Cr.fal, crista falciformis; Exo, exoccipital; 34 Fm, foramen magnum; Oc, occipital condyle; Of, otic flange; On, otic notch; Ppa, postparietal; Pq.f, 35 paraquadrate foramen; Pt, pterygoid; Pt.f, posttemporal foramen; Q, quadrate; Qj, quadratojugal; Sq, squamosal; Tab, tabular. 36 37 165x125mm (300 x 300 DPI) 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Palaeontology Page 56 of 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 FIG. 5. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the 20 Argana Basin, Morocco: MNHN.F.ARG 3. Complete right hemi-mandible in labial view, A, photograph; B, 21 interpretive drawing; and lingual view, C, photograph; D, interpretive drawing. Scale bars represent 10 cm. 22 Anatomical abbreviations: Am.c, accessory mandibular canal; aMf, anterior Meckelian fenestra; Ang, 23 angular; Art, articular; Co1, anterior coronoid; Co2, intercoronoid; Co3, posterior coronoid; De, dentary; Glf, 24 glenoid fossa; Im.c, inferior mandibular canal; Par, prearticular; poGl.Pr, postglenoid process; pMf, posterior 25 Mekelian fenestra; poSp, postsplenial; prGl.Pr, preglenoid process; Rart.Pr, retroarticular process; Sang, surangular; Sm.c, superior mandibular canal; Sp, splenial; Sy, symphysis. 26 27 165x63mm (300 x 300 DPI) 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Page 57 of 60 Palaeontology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 FIG. 6. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the Argana Basin, Morocco: MNHN.F.ARG9-1-3, paratype, articulated clavicles MNHN.F.ARG 9.1 and 21 MNHN.F.ARG 9.2 and interclavicle MNHN.F.ARG 9.3 in ventral view. A, photograph; B, interpretive drawing. 22 Scale bars represent 15 cm. Anatomical abbreviations: Cl, clavicle; Cl.c, clavicular canal; Ic, interclavicle. 23 24 166x64mm (300 x 300 DPI) 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Palaeontology Page 58 of 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 FIG. 7. Arganasaurus (Metoposaurus) azerouali (Dutuit, 1976) comb. nov., from the Late Triassic of the Argana Basin, Morocco: MNHN.F.TAL 12, isolated radius encased in the ventral surface of the skull fragment. 30 Anatomical abbreviations: Orb, orbit; Ra, radius. 31 32 80x54mm (300 x 300 DPI) 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Page 59 of 60 Palaeontology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 FIG. 8. Phylogeny of the Metoposauroidea and position of Arganasaurus (Metoposaurus) azerouali (Dutuit, 30 1976) comb. nov.. Strict consensus of three most parsimonious trees (L=143; CI = 0.5385; RI = 0.6118, 31 see text) mapped on the stratigraphic chart of the Middle and Late Triassic (stratigraphic chart after Cohen et al. 2018). Node labels: Node letter/Bremer support value (when above 1). Black bars indicate the 32 unambiguous stratigraphic distribution of the taxa and dotted lines indicate the range of uncertainty of this 33 distribution. CPE scale bar represents the duration of the Carnian Pluvial Episode (dated according to Dal 34 Corso et al. 2018). Abbreviations: Myr, million years. Carn., Carnian; Hett., Hettangian; Ladin., Ladinian; 35 Rhaet., Rhaetian; Sinem., Sinemurian. 36 37 165x114mm (300 x 300 DPI) 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology Palaeontology Page 60 of 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 FIG. 9. Correlation chart of all the Late Triassic metoposauroid-bearing formations across Pangaea. Stratigraphic chart after Cohen et al. (2018), uncertainty on the duration of the Norian stage collowing Ogg 30 et al. (2014), Land Vertebrate Faunachrons (LVF) according to Lucas (2018b) and Carnian Pluvial Episode 31 (CPE, in blue) dated according to Dal Corso et al. (2018). Dotted lines indicate an uncertain age and arrows 32 indicate the extent of this uncertainty. Abbreviations: Adam., Adamanian; Alaun., Alaunian; Apach., 33 Apachean; Berdyan., Berdyankian; Fass., Fassanian; Fm., Formation; Longob., Longobardian; Mb., Member; 34 Otisch., Otischalkian; Perov., Perovkan; Revuel., Revueltian; Sevat., Sevatian; Tuval., Tuvalian; Wass., 35 Wassonian. 36 165x112mm (300 x 300 DPI) 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Palaeontology