Jeremy E Martin
email: jeremy.martin@ens-lyon.fr

New material of the ziphodont mesoeucrocodylian Iberosuchus from the Eocene of Languedoc, southern France Nouveau matériel du crocodylomorphe ziphodonte Iberosuchus de

Keywords: Comparative anatomy, Sebecosuchia, Eocene, France

Skull fragments and osteoderms assigned to Iberosuchus sp. are described from three middle Eocene localities: Aumelas, Robiac and Saint-Martin-de-Londres in Languedoc, southern France. These remains expand the anatomical knowledge of this poorly known taxon, notably on the morphology of the premaxilla, maxilla, postorbital and jugal and allow a comparison with other non-eusuchian ziphodont mesoeucrocodylians. A close relationship of the genus Iberosuchus with narrow/elevated-snouted Baurusuchidae or Peirosauridae from the Cretaceous of South America and Africa appears unlikely. Affinities between Iberosuchus and Sebecidae, a group reported from the Cenozoic of South America; are suspected but require further testing. The record of Iberosuchus is limited to the European middle Eocene (Lutetian and Bartonian) and it is currently known from Portugal, Spain and France. RÉSUMÉ-Des morceaux crâniens et des osteoderms sont décrits en provenance de trois gisements de l'Eocène moyen du Languedoc, sud de la France : Aumelas, Robiac et Saint-Martin-de-Londres, et assignés au crocodylomorphe ziphodonte Iberosuchus sp.. Bien que fragmentaires, ces restes élargissent les connaissances sur l'anatomie de ce taxon mal connu, notamment sur la morphologie du prémaxillaire, du maxillaire, du postorbital et du jugal et autorisent une comparaison avec d'autres mesoeucrocodyliens ziphodontes non-eusuchiens. Le genre Iberosuchus ne ressemble à aucun crocodylomorphe à museau étroit et surélevé du Crétacé d'Amérique du Sud ou d'Afrique, tels les Baurusuchidae ou les Peirosauridae. En revanche, des similarités sont notées entre Iberosuchus et les Sebecidae, un groupe connu dans le Cénozoïque d'Amérique du Sud, évoquant un lien possible entre ces deux taxons mais qui requiert de futures études. Iberosuchus n'est connu que dans l'Eocène moyen (Lutétien et Bartonien) d'Europe et est mentionné au Portugal, en Espagne ainsi qu'en France.

Introduction

Amidst the rich mammalian faunas, Eocene continental assemblages of Europe contain ziphodont mesoeucrocodylians with serrated and labiolingually compressed teeth.

Europe is unique at that time for hosting two distantly related lineages with convergent cranial morphologies. On one hand, the eusuchian Pristichampsus rollinati, recently moved into the genus Boverisuchus [START_REF] Brochu | Phylogenetic relationships of Palaeogene ziphodont eusuchians and the status of Pristichampsus Gervais, 1853[END_REF], is known from French and German Lutetian deposits and is represented by well-preserved skeletons from Geiseltal (e.g. [START_REF] Brochu | Phylogenetic relationships of Palaeogene ziphodont eusuchians and the status of Pristichampsus Gervais, 1853[END_REF].

The affinities of the second lineage, possibly related to the Sebecosuchia, remain obscure due to the scarcity of specimens. Sebecosuchia comprise the Sebecidae and the Baurusuchidae, primarily reported from South America (e.g. [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF][START_REF] Buffetaut | Découverte du crocodilien Sebecus dans le Miocène du Pérou oriental[END_REF]Buffetaut, 1982;Turner and Sertich, 2010;[START_REF] Pol | Postcranial anatomy of Sebecus icaeorhinus (Crocodyliformes, Sebecidae) from the Eocene of Patagonia[END_REF]. Distinguishing Pristichampsus and Sebecosuchia on the basis of tooth morphology has not proved conclusive yet [START_REF] Antunes | Iberosuchus et Pristichampsus, crocodiliens de l'éocène, données complémentaires, discussion, distribution stratigraphique[END_REF]Legasa et al., 1993;[START_REF] Brochu | Phylogenetic relationships of Palaeogene ziphodont eusuchians and the status of Pristichampsus Gervais, 1853[END_REF] and their identification will have to rely on the identification of cranial and postcranial elements. [START_REF] Berg | Die Krokodile, insbesondere Asiatosuchus und aff. Sebecus?, aus dem Eozän von Messel bei Darmstadt/Hessen[END_REF] first recognized 'aff. Sebecus? n. sp.' for a fragmentary rostrum and a lower jaw from the Lutetian of Messel pit in Germany, suggesting the first referral to Sebecosuchia in Europe. Two ziphodont 'mesosuchians' were then named from the Eocene of Europe: Bergisuchus dietrichbergi [START_REF] Kuhn | Die vorzeitlichen Krokodile[END_REF] for the aforementioned german specimen, and Iberosuchus macrodon [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF] for a rostrum from the Lutetian of Vale Furado, Portugal. Unsurprisingly, the anatomy and affinities of these animals remains poorly known.

Bergisuchus and Iberosuchus have been interpreted as members of the Sebecosuchia and more precisely to be part of the Baurusuchidae [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF][START_REF] Buffetaut | Histoire biogéographique des Sebecosuchia (Crocodylia, Mesosuchia) : un essai d'interprétation[END_REF]Buffetaut, 1982). Then, both taxa were viewed as European members of the family Trematochampsidae [START_REF] Buffetaut | The ziphodont mesosuchian crocodile from Messel: a reassessment[END_REF] or closer to Sebecus than to Trematochampsidae for Bergisuchus [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF]. [START_REF] Gasparini | New tertiary Sebecosuchia (Crocodylia: Mesosuchia) from Argentina[END_REF] concluded that the affinities of Iberosuchus macrodon were uncertain because the premaxilla combines characters of the Baurusuchidae and Sebecidae (such as the recess for reception of the hypertrophied mandibular fourth tooth), but that contrary to these groups, the premaxilla bears five alveoli instead of four.

The first phylogenetic explorations found Iberosuchus as a possible member of the Sebecosuchia and recovered a polyphyletic trematochampsid clade [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF]. A sebecosuchian affinity was confirmed in Turner and Sertich (2010), and Iberosuchus and Bergisuchus were considered non-sebecid sebecosuchians in other phylogenetic analyses that included other baurusuchid and sebecid taxa [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF][START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF][START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF][START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF]. Therefore, Bergisuchus and Iberosuchus seem to belong to the Sebecosuchia ((Sebecidae + Baurusuchidae) according [START_REF] Pol | Postcranial anatomy of Sebecus icaeorhinus (Crocodyliformes, Sebecidae) from the Eocene of Patagonia[END_REF]. However, the phylogenetic position of Sebecidae is debatable, and they have been allied with Peirosauridae [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF]. More recently, [START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF] highlighted that sebecids together with Iberosuchus and Bergisuchus share derived similarities with baurusuchids and with peirosaurids. Therefore, the placement of Bergisuchus and Iberosuchus has yet to be explored.

Here, I report new specimens from three Eocene localities in Languedoc, southern France, which despite their fragmentary nature can be attributed to Iberosuchus sp. Their description provides a basis for comparing the genus Iberosuchus to other non-eusuchian ziphodont mesoeucrocodylians from Europe and Gondwana and although the new material does not add a sufficient number of characters for a phylogenetic analysis, its affinities are preliminary discussed with a focus on the Sebecosuchia (Sebecidae + Baurusuchidae sensu [START_REF] Pol | Postcranial anatomy of Sebecus icaeorhinus (Crocodyliformes, Sebecidae) from the Eocene of Patagonia[END_REF] with which it has previously been allied [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF]Turner and Sertich, 2010;[START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF] as well as the Peirosauridae, which are allied to the Sebecidae under the phylogenetic hypothesis of [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF].

All the specimens presented here are housed in ISEM, Institut des Sciences de l'Évolution de Montpellier, Université de Montpellier, France, and bear the following acronyms: RBN, Robiac Nord, Gard, France; SMF, St-Martin de Londres, Hérault, France; AUM, Aumelas, Hérault, France.

Geological setting

The material described herein comes from three localities of the Languedoc in southern France. All the localities correspond to Eocene continental deposits, whose ages were established according to the European Mammal Paleogene (MP) zonation (Biochro'M, 1997). Aumelas (Hérault) is considered to be the oldest of the three and is attributed a MP13 age according to [START_REF] Escarguel | Sur l'âge numérique des faunes de mammifères du paléogène d'Europe occidentale, en particulier celles de l'éocène inférieur et moyen[END_REF], therefore possibly Lutetian. The outcrop consists of a lacustrine limestone and acid-preparation is therefore necessary to free specimens from their carbonate matrix [START_REF] Sudre | Aumelasia gabineaudi n.g. n.sp. Nouveau Dichobunidae (Artiodactyla, Mammalia) du gisement d'Aumelas (Hérault) d'âge lutétien terminal. Palaeovertebrata, Mémoire Jubilaire en hommage à[END_REF]. Saint-Martin-de-Londres (Hérault) assigned to MP15 [START_REF] Escarguel | Sur l'âge numérique des faunes de mammifères du paléogène d'Europe occidentale, en particulier celles de l'éocène inférieur et moyen[END_REF] could either be late Lutetian or Bartonian in age. The locality consists of a fossiliferous lens located at the base of limestones containing the freshwater gastropod Australorbis pseudoammonius [START_REF] Crochet | Découverte dans le bassin de Saint-Martin-de-Londres (Hérault, Sud de la France) d'un gisement à vertébrés continentaux d'âge Eocène moyen[END_REF]. Bones are included in a carbonaceous mud and the site yielded a diverse mammalian fauna together with yet indeterminate remains of birds and a herpetofaunal assemblage [START_REF] Crochet | Découverte dans le bassin de Saint-Martin-de-Londres (Hérault, Sud de la France) d'un gisement à vertébrés continentaux d'âge Eocène moyen[END_REF]. Finally, the locality of Robiac (Gard) [START_REF] Sudre | Les gisements de Robiac et leurs faunes de mammifères[END_REF] assigned to MP16 [START_REF] Escarguel | Sur l'âge numérique des faunes de mammifères du paléogène d'Europe occidentale, en particulier celles de l'éocène inférieur et moyen[END_REF]) might be considered Bartonian in age. Several ziphodont teeth from this locality, housed in the Muséum National d'Histoire Naturelle, Paris have been attributed to the genera Pristichampsus ( = Boverisuchus) and to Iberosuchus by [START_REF] Antunes | Iberosuchus et Pristichampsus, crocodiliens de l'éocène, données complémentaires, discussion, distribution stratigraphique[END_REF].

Systematic Palaeontology

MESOEUCROCODYLIA [START_REF] Whetstone | A 'cursorial' crocodilian from the Triassic of Lesotho (Basutoland), southern Africa[END_REF]Whybrow, 1983 SEBECOSUCHIA Simpson, 1937 Genus Iberosuchus [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF] Iberosuchus sp.

Figs. 2-6

Referred Specimens. AUM 466, AUM 474, AUM 477, SMF 203: premaxillae;RBN 2026, SMF 181: maxillae;AUM 465: left postorbital;AUM 472: left jugal;SMF 206: a large isolated tooth;RBN 201, 2012RBN 201, , 2014RBN 201, , 2018RBN 201, , 2019RBN 201, , 2020RBN 201, , 2021RBN 201, , 2023RBN 201, , 2816;;AUM 458, AUM 459: osteoderms.

Description

Skull:

Premaxilla -Three specimens come from Aumelas and include an almost complete right element (AUM 474, Fig. 2A,B), a fragment of a right element (AUM 466, Fig. 2C-F), and a pair of premaxillae pressed against each other (AUM 477). Ornamentation of the external surface of these premaxillae is vermiculate. The morphology of AUM 477 corresponds to that described for AUM 466 and AUM 474 in displaying a marked concave notch visible on both elements for the reception of the dentary tooth, as well as the posterior premaxillary foramen visible on the palatal surface of the right element. The size of AUM 477 is about three times larger than the other specimens described below. A right complete premaxilla bearing one tooth in the last alveolus comes from Saint-Martin-de-Londres (SMF 203, Fig. 3A-C) and is the largest of all specimens.

AUM 474 is almost complete and only misses its premaxillary dorsal process. AUM 466 is more fragmentary being represented by the posterior area and the premaxillary dorsal process. In all cases, the premaxilla is taller than long. The external nares face anteriorly and according to AUM 466, which preserves the suture for the nasal, this bone participates in the posterodorsal margin of the external nares as in the holotype [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF]. The ornamented lateral surface of the premaxilla consists of a distinct bony ridge that makes the vertical lateral margin of the naris. The anterior end of the premaxilla makes the ventral margin of the naris, is devoid of ornamentation and is visible in dorsal view. This area is flush against the anterior margin of the premaxilla, where a few foramina open above the tooth row.

The lateral border of the naris is marked internally by a narrow and vertical incision or narial recess, obvious in AUM 474 and SMF 203 (Figs. 2F,3A). In ventral view, the suture for the maxilla is visible and forms the ventral margin of the narial canal, thus the maxilla attains the level of the last premaxillary alveolus. The complete premaxillary tooth row of AUM 474 and SMF 203 presents five alveoli (Figs. 2E,3C), all of them subcircular in outline as in the holotype (pl. VII in [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF]. All the alveoli are separated from each other. They increase in diameter until the fourth, which is the largest. The last alveolus is of the same size as the third and is not in line with the other alveoli; it opens more dorsally, near the level of the premaxillary notch. Two excavated and deep pits are located immediately lingual to the tooth row between the second and third, then between the third and fourth alveoli. Anterior to the suture with the maxilla, the ventrolateral margin of the premaxilla bears a deep concave notch for reception of the largest dentary tooth as in the holotype [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF]. In ventral view, this notch is delimited medially by a bony ridge, which stands out from the palatal surface of the premaxilla. Medial to this ridge, the palatal surface of the premaxilla is not flat but is deeply concave. Posteriorly along this concavity, a foramen opens ventrally on the premaxillary-maxillary suture as in Pabwehshi pakistanensis [START_REF] Wilson | New crocodyliform (Reptilia, Mesoeucrocodylia) from the Upper Cretaceous Pab Formation of Vitakri, Balochistan (Pakistan)[END_REF] and Hamadasuchus rebouli [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF]. This foramen is visible in AUM 474, AUM 466, SMF 203 and seems visible but broken in the holotype (pl. VII in [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF].

Maxilla -Two fragments of maxillae are recognized from Robiac (RBN 2026) and Saint-Martin-de-Londres (SMF 181; Fig. 3). RBN 2026 represents a posterior fragment of a right maxilla hosting two broken ziphodont tooth crowns. SMF 181 is a larger portion of a right maxilla. In both specimens, the lateral surface of the bone is vermiculate. The maxilla RBN 2026 has a vertical lateral surface; however, as seen in anterior view, the lateral margin close to the tooth row is not vertical but is beveled and faces lateroventrally. Alveoli are mediolaterally compressed. Medially, no palatal process of the maxilla is present but the suture for the ectopterygoid is visible. SMF 181 is a right element from the anterior region of the maxilla. The lateral surface of this maxilla is completely vertical being twice as tall as the complete associated tooth crown. Six alveoli are visible, which are all mediolaterally compressed and their long axis has an oblique direction. The largest of all may correspond to the third alveolus. [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF] reported that the second maxillary alveolus could be the largest but he observed that the third is incomplete. The collars of all alveoli are indented and in medial view, the alveolar walls are clearly individualized and run for most of the height of the maxilla. Foramina are visible dorsal to the alveoli along the medial maxillary surface. The palatal shelf is not well preserved but can be located far dorsally, at about mid-level of the maxillary height. In anterior view, the internal alveolar wall of the broken alveolus reveals a net of more or less vertical furrows.

Nasal -A fragment of the paired nasals is preserved from Aumelas (AUM 471; Fig. 2O,P). The dorsal surface of the nasal is slightly convex. In dorsal view, the vermiculate ornamentation is too dense to allow discerning the median suture as in the holotype [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF]. The suture between the nasals consists of a straight line only visible in the ventral surface. Here, the nasals merge into a thin ridge following the suture. Opening ventrally, a pair of foramina is centered on each nasal. Each nasal is ventrally concave and their lateral wall is oblique. Laterally, the nasal accommodates a dorsoventrally high suture for the maxilla. Although the preserved portion of the nasals is short, the nasals narrow in their anterior portion.

Postorbital -A nearly complete left isolated postorbital comes from Aumelas (AUM 465; Fig. 2G-K) and closely resembles the postorbital of the Spanish Iberosuchus macrodon from Aldealengua (Ortega, 2004, unpublished). The dorsal surface is vermiculate. The postorbital has a distinct anterolateral process, the dorsal surface of which is demarcated from the dorsal surface of the postorbital by a concave notch. Possibly, this process or facet would accommodate a palpebral bone (arrow in Fig. 2H,I,K). The sutures with the frontal and the squamosal are not preserved and it is thus impossible to assess the participation of the postorbital to the infratemporal fenestra. The postorbital builds the anterolateral margin of the supratemporal fenestra but does not overhang this fenestra. Medially, the posterior region of the supratemporal wall of the postorbital presents a wide sutural area for the reception of a lamina (stipple line in Fig. 2G). It is unknown whether this sutural area accommodates a medial contribution of the squamosal or a process of the laterosphenoid. Two small foramina are observed just anterior to this lamina. The postorbital is vertical and triangular in cross section, and slightly concave on each side. No foramen is detected on the bar. The postorbital suture for the jugal is strongly indented and is visible in lateral view. Accordingly, the jugal ascends far dorsally on the lateral margin of the bar whereas the postorbital reaches far ventrally on the medial side of the bar. Dorsally, the posterior margin of the postorbital is deeply inset into a concave and smooth structure. The postorbital bar is roofed by the anterolateral process of the postorbital.

Jugal -A left isolated jugal is identified from Aumelas (AUM 472; Fig. 2L-N). Its anterior process and part of the posterior process are not preserved. Its lateral surface bears faint vermiculate ornamentation as in other bones, rather than pits. The jugal is mediolaterally compressed, with an ovoid section in posterior view. The jugal process of the postorbital bar has the shape of a pillar, is mesiodistally compressed in cross section and devoid of ornamentation. In lateral view, the postorbital bar is nearly perpendicular, albeit slightly bent posteriorly to the posterior process of the jugal. The lateral margin of the postorbital bar is not inset from the lateral rugose surface of the bone but is flush against it. The postorbital bar described in the ziphodont 'mesosuchian' from La Livinière, Hérault, France is also not inset medially [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF]. However, the two jugal specimens from La Livinière are fragmentary and further comparison with the jugal from Aumelas is limited to the similar sculpturing pattern on the external surface. On the anterior corner of the bar of AUM 472, a bony ridge separates the bar from the lateral surface of the bone. Here, a small circular perforation (diameter = 2 mm) of the jugal is visible. In medial view, the large sutural area for the ectopterygoid indicates that the ectopterygoid posterior process is short, reaching at about the same level as the jugal bar. Dorsally, the entire medial surface of the bar accommodates a sutural area that could correspond to the descending process of the postorbital. Ventrally, the jugal presents a transverse trough bearing a set of equally spaced foramina. This trough is bordered by a thick ridge, delimiting the lateral surface from the ventral surface. In lateral view, the ventral margin of the jugal is not straight with the anterior region curving ventrally.

However, the presence of a notch at the level of the ectopterygoid suture (see [START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF] could not be assessed with confidence.

Dentition -All of the teeth, including those preserved in premaxillae and maxillae are ziphodont (Figs. 4,5). They are labiolingually compressed with clearly individualized denticles on the mesiodistal carinae. The premaxilla AUM 466 hosts a replacement tooth, visible in the broken fourth alveolus (Fig. 5C). The tooth displays individualized denticles on the mesial carina. The distal carina is not visible. The denticles spread for the whole crown length. AUM 477 also hosts two replacement teeth with the same morphology; one in the last alveolus of the left premaxilla, another one is heavily damaged and occurs in a break of the bone. As an example of a large isolated tooth, SMF 206 (Fig. 4) shows that the crown is not symmetrical but the apex is distally curved. The crown is thick and flat compared to the mesial and distal margins, which gradually become thinner before merging along the carina.

Postcranial Skeleton:

Osteoderms -A number of osteoderms are preserved in Robiac (Fig. 6) and are identical to osteoderms reported from other localities in Spain (Martín de [START_REF] Martín De Jesús | Los Crocodylia del Eoceno y Oligoceno de la Cuenca del Duero. Dientes y Osteodermos[END_REF][START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF]. They display a tall ridge of variable extent surrounded by smaller ridges radiating around it. For example, in a series of small osteoderms (RBN 2018(RBN , 2020(RBN , 2019(RBN , 2021(RBN , 2012(RBN , 2023)), one ridge runs for almost the entire length of the osteoderm and culminates into a spine near the anterior or posterior edge of the osteoderm where two lateral accessory processes join, so that in dorsal view, the ridge has the shape of a cross. This morphology of the ridge is also observed in larger osteoderms, but the main body of the osteoderms is flat, ovoid or rectangular in outline (RBN 2816(RBN , 2014(RBN , 2013)). The whole outline of the osteoderm is strongly indented. The ventral surface is flat in large osteoderms and concave in small ones. Two osteoderms (AUM 458 and AUM 459, Fig. 6X-C1) are longer than wide with a nearly rectangular outline as reported in [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF] and [START_REF] Martin | A sebecosuchian in a middle Eocene karst with comments on the dorsal shield in Crocodylomorpha[END_REF].

They bear a shallow median ridge associated to radiating vermiculate smaller ridges. Their long margin is serrated and the anterior margin is smooth and convex whereas the posterior margin is beveled in dorsal view.

Discussion

Assignment to the genus Iberosuchus

The record of non-eusuchian ziphodonts from the Eocene of Europe consists of fragmentary remains [START_REF] Berg | Die Krokodile, insbesondere Asiatosuchus und aff. Sebecus?, aus dem Eozän von Messel bei Darmstadt/Hessen[END_REF][START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF][START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF][START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF]. Since the first mention of [START_REF] Berg | Die Krokodile, insbesondere Asiatosuchus und aff. Sebecus?, aus dem Eozän von Messel bei Darmstadt/Hessen[END_REF], only two taxa have been formally erected, Bergisuchus dietrichbergi [START_REF] Kuhn | Die vorzeitlichen Krokodile[END_REF] and Iberosuchus macrodon Antunes 1975. Additional skull material from the Eocene of Tosalet del Morral, Lerida province, Spain has been considered to be reminiscent of Iberosuchus macrodon (Buffetaut, 1982;[START_REF] Buffetaut | The ziphodont mesosuchian crocodile from Messel: a reassessment[END_REF][START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF]. [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF] reassigned to cf. Iberosuchus historical specimens consisting of mandibular remains, from the Eocene of Issel, France and Caenes, Spain based on tooth morphology and mandibular characters. [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF] reported two mandibles that were referred to Bergisuchus cf. dietrichbergi from the middle Eocene of Geiseltal, Germany. Other remains of uncertain affinities were reported by [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF] and consist of a jugal, vertebrae and isolated teeth from La Livinière, Hérault, France. [START_REF] Ortega | El cocodrilo de El Viso (Eoceno, Zamora): consideraciones acerca de los «zifodontos» (Metasuchia,?Sebecosuchia) del Eoceno de la cuenca del Duero[END_REF] reported a fragmentary skull and mandibular elements from the Eocene of el Cerro de El Viso, Zamora, Spain. These later remains have been described in [START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF] and they represent the most complete remains attributable to Iberosuchus. [START_REF] Antunes | Iberosuchus, crocodile Sébécosuchien nouveau, l'Eocène ibérique au Nord de la chaîne centrale, et l'origine du canyon de Nazaré[END_REF] advanced that the material they described from Vale Furado could not be referred to Bergisuchus dietrichbergi because that taxon is characterized by a denser ornamentation of the premaxilla, by the absence of a notch for reception of the fourth mandibular tooth, and by smaller and possibly more numerous maxillary teeth. [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF] also noted differences between cf. Iberosuchus and Bergisuchus, notably in the sculpturing, tooth count, shape of the dentary, and in the diameter of the fourth enlarged dentary tooth. At least based on sculpturing, the specimens from Aumelas, Robiac and Saint-Martin-de-Londres cannot be allied to Bergisuchus dietrichbergi. Buffetaut (1982;[START_REF] Buffetaut | The ziphodont mesosuchian crocodile from Messel: a reassessment[END_REF] briefly reported a rostrum from the Eocene of Tosalet del Morral, Spain as being very similar to Iberosuchus but also bearing similarities with Bergisuchus. This important specimen was also discussed by [START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF], and matches the morphology of the herein described material from southern France and Portugal in: 1) the same tooth counts and dental arrangement in the premaxillae; 2) similar tooth proportions in the maxilla, with a large third tooth followed by smaller fourth and fifth teeth; 3) teeth slightly compressed; 4) the presence of a notch at the level of the premaxillary-maxillary suture. The premaxillae from Aumelas and Saint-Martin-de-Londres closely match the holotype of Iberosuchus macrodon in presenting the same alveolar count, a recess along the posterior and ventral narial borders, the subcircular contour of the alveoli, and in being taller than wide. The largest maxillary alveolus in the specimen of Saint-Martin-de-Londres is the third as in the specimen from Tosalet del Morral. The presence of a palatal foramen at the premaxillary-maxillary suture is attested in the premaxillae of Aumelas, Saint-Martin-de-Londres, Tosalet del Morral and Vale Furado. Furthermore, the postorbital from Aumelas is comparable to the postorbital of Iberosuchus from Salamanca, Spain (Ortega, 2004, Fig. 5.6) in presenting a notch that may accommodate a palpebral. Finally, osteoderms described here from Languedoc with their peculiar crested or vermiculate ornamentation (Fig. 6) have previously been reported from Spain (Martín de [START_REF] Martín De Jesús | Los Crocodylia del Eoceno y Oligoceno de la Cuenca del Duero. Dientes y Osteodermos[END_REF][START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF] or from France [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF][START_REF] Martin | A sebecosuchian in a middle Eocene karst with comments on the dorsal shield in Crocodylomorpha[END_REF] and provide additional evidence for a referral to the genus Iberosuchus.

Because they are directly comparable to the material from Portugal and Spain, the specimens described here from the French middle Eocene localities of Aumelas, Saint-Martin-de-Londres and Robiac are ascribed to Iberosuchus sp.. Although comparative material is extremely limited, the jugal from Aumelas is similar to that of La Livinière [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF]. Both share the same sculpturing pattern, and a postorbital bar, which is not inset from the lateral surface. It appears plausible that the material from La Livinière can be ascribed to the genus Iberosuchus but until more material becomes available it is referred to cf. Iberosuchus.

Comparison with other ziphodont mesoeucrocodylians

Although there is presently not enough characters to attempt a phylogenetic analysis, the strong similarities between the specimens from Languedoc and Iberosuchus allow comparisons with the three relevant groups with close affiliates to Iberosuchus: Baurusuchidae, Peirosauridae, and Sebecidae [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF]Turner and Sertich, 2010;[START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF][START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF][START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF]. Baurusuchidae is a taxon restricted to the Cretaceous of Brazil, Argentina and possibly India (e.g. Montefeltro et al. 2011). Peirosauridae, which are mostly from the Cretaceous of Argentina and Brazil, includes seven species (see [START_REF] Martinelli | A new peirosaurid from the Upper Cretaceous of Argentina: Implications for specimens referred to Peirosaurus torminni Price (Crocodyliformes: Peirosauridae)[END_REF] as well as a taxon from the Cretaceous of Morocco (Turner and Sertich, 2010) referred as Hamadasuchus rebouli by [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF].

Sebecidae are exclusively known in the Cenozoic of South America [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF][START_REF] Busbey | New material of Sebecus cf. huilensis (Crocodilia: Sebecosuchidae) from the Miocene La Venta Formation of Colombia[END_REF][START_REF] Buffetaut | A new crocodilian, Sebecus querejazus, nov. sp. (Mesosuchia, Sebecidae) from the Santa Lucia Formation (Early Paleocene) at Vila Vila, southcentral Bolivia[END_REF][START_REF] Gasparini | New tertiary sebecosuchians (Crocodylomorpha) from South America: phylogenetic implications[END_REF][START_REF] Paolillo | Nuevos cocodrilos Sebecosuchia del Cenozoico suramericano (Mesosuchia: Crocodylia)[END_REF][START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF][START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF][START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF].

In Iberosuchus, the ziphodont dentition, the oreinirostral morphology, the presence of an enlarged third maxillary tooth (see also [START_REF] Buffetaut | The ziphodont mesosuchian crocodile from Messel: a reassessment[END_REF] for the specimen from Tosalet del Moral, Spain), the conical cross section of the premaxillary dentition, the presence of an antorbital fenestra [START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF], the presence of a palpebral, and the excavated notch at the premaxillary-maxillary suture for reception of the enlarged fourth dentary tooth, all indicate a suite of shared characters with members of the Baurusuchidae, Peirosauridae and Sebecidae.

In fact, among mesoeucrocodylians, the presence of labiolingually compressed and serrated teeth -the ziphodont condition of Langston (1975); see also [START_REF] Legasa | The serrated teeth of Sebecus and the Iberoccitanian crocodile, a morphological and ultrastructural comparison[END_REF] -arose in distantly related lineages, some with a possible terrestrial habit such as Araripesuchus wegeneri (Prasad and de Lapparent de Broin, 2002) and in some eusuchians (e.g. [START_REF] Rossmann | Studien an känozoischen Krokodilen: 1. Die paläoökologische Bedeutung des eusuchen Krokodils Pristichampsus rollinatii (Gray) für die Fossillagerstätte Grube Messel[END_REF]. Iberosuchus shares other characters with Baurusuchidae, Peirosauridae and Sebecidae in possessing a palatal foramen on the premaxillary-maxillary suture as occurs in the following sebecids: Lorosuchus nodosus from the Paleocene of Argentina [START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF] and possibly in Sebecus icaeorhinus from the Eocene of Argentina (see plate 12 in [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF] and Ayllusuchus fernandezi from the Eocene of Argentina (see fig. 2 in [START_REF] Gasparini | New tertiary Sebecosuchia (Crocodylia: Mesosuchia) from Argentina[END_REF]. Such a palatal foramen is also present in the peirosaurid Hamadasuchus rebouli from the Cretaceous of Morocco [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF] and finally in Pabwehshi pakistanensis from the Cretaceous of Pakistan, a taxon interpreted as a baurusuchid [START_REF] Wilson | New crocodyliform (Reptilia, Mesoeucrocodylia) from the Upper Cretaceous Pab Formation of Vitakri, Balochistan (Pakistan)[END_REF]. Among the Baurusuchidae, Peirosauridae and Sebecidae, the presence of an antorbital fenestra is variable and does not preferably indicate a particular affinity. For example, the antorbital fenestra is preserved in the peirosaurids Pepesuchus deseae, Montealtosuchus arrudacamposi, Uberabasuchus terrificus, Hamadasuchus rebouli and Lomasuchus palpebrosus [START_REF] Campos | On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil[END_REF][START_REF] Carvalho | Uberabasuchus terrificus sp. Nov., a new crocodylomorpha from the Bauru Basin (Upper Cretaceous), Brazil[END_REF]2007;[START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF][START_REF] Gasparini | A new Senonian peirosaurid (Crocodylomorpha) from Argentina and a synopsis of the South American Cretaceous crocodilians[END_REF]. The baurusuchids Baurusuchus salgadoensis and Campinasuchus dinizi possess an antorbital fenestra whereas Stratiotosuchus maxhechti and Pissarrachampsa serra lack this feature [START_REF] Riff | Baurusuchid crocodyliforms as theropod mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti (Upper Cretaceous of Brazil)[END_REF]Montelfreto et al., 2011). An antorbital fenestra has not been identified in the Sebecidae, although two equivocal members Zulmasuchus querejazus [START_REF] Buffetaut | A new crocodilian, Sebecus querejazus, nov. sp. (Mesosuchia, Sebecidae) from the Santa Lucia Formation (Early Paleocene) at Vila Vila, southcentral Bolivia[END_REF] and Bretesuchus bonapartei [START_REF] Gasparini | New tertiary sebecosuchians (Crocodylomorpha) from South America: phylogenetic implications[END_REF] display a depression on the lacrimal, corresponding to the likely position of this fenestra. In addition, the antorbital fenestra has been tentatively identified in Sahitisuchus fluminensis [START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF]. The area is otherwise unknown in other sebecids such as Ayllusuchus fernandezi [START_REF] Gasparini | New tertiary Sebecosuchia (Crocodylia: Mesosuchia) from Argentina[END_REF] or Langstonia huilensis [START_REF] Langston | Ziphodont crocodiles: Pristichampsus vorax (Troxell), new combination, from the Eocene of North America[END_REF]. The anterolateral corner of the postorbital of Iberosuchus possesses a facet, possibly for the accommodation of a palpebral. A palpebral facet on the postorbital has been reported in the baurusuchid Campinasuchus dinizi [START_REF] Campos | On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil[END_REF], in the peirosaurid Hamadasuchus rebouli [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF] and in Pepesuchus desea [START_REF] Campos | On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil[END_REF]. Complete palpebrals are known in the baurusuchids Baurusuchus albertoi, Baurusuchus salgadoensis, Gondwanasuchus scabrosus [START_REF] Marinho | Gondwanasuchus scabrosus gen. et sp. nov., a new terrestrial predatory crocodyliform (Mesoeucrocodylia: Baurusuchidae) from the Late Cretaceous bauru Basin of Brazil[END_REF], Stratiotosuchus maxhechti [START_REF] Riff | Baurusuchid crocodyliforms as theropod mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti (Upper Cretaceous of Brazil)[END_REF] and Pissarrachampsa serra (Montelfreto et al., 2011), and also in the peirosaurids Lomasuchus palpebrosus and Montealtosuchus arrudacamposi (Carvalho et al., 2007). [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF] described a triangular palpebral attached to the anterior margin of the orbit in the sebecid Sebecus icaeorhinus (possibly, a posterior palpebral was present). Considering all those evidences, the presence of a ziphodont dentition, a palatal foramen, an antorbital fenestra and palpebral, are widely distributed characters among Baurusuchidae, Peirosauridae and Sebecidae. Nevertheless, Iberosuchus also presents characters found in each of these three families and these are reviewed below.

With Peirosauridae, Iberosuchus displays two synapomorphies based on the framework of Larsson and Sues (2007, p. 552): the presence of five premaxillary teeth and the anterior two premaxillary alveoli nearly confluent. These characters are clearly visible in the specimens from Aumelas (Fig. 2B,2E) and Saint-Martin-de-Londres (fig. 3C), in the rostrum from Tosalet del Morral (Buffetaut, 1982, fig. 1) and in the holotype of Iberosuchus macrodon (Antunes, 1975, pl. VII, fig. 17) and relying on such characters would indicate a peirosaurid affinity for Iberosuchus. However, the recently described peirosaurid Montealtosuchus arrudacamposi does not have confluent premaxillary teeth and the specimen assigned to Hamadasuchus rebouli [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF] possesses four premaxillary alveoli only. Turner and Sertich (2010, p. 208) coded Iberosuchus macrodon on the basis of the datamatrix of [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF] and found that this genus shares with Peirosauridae the extremely large perinarial fossa (also present in Baurusuchidae, e.g. [START_REF] Riff | Baurusuchid crocodyliforms as theropod mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti (Upper Cretaceous of Brazil)[END_REF] and the wedge-like process of the maxilla in lateral view at the premaxillary-maxillary suture.

However, comparing Iberosuchus with the best-represented members of the Peirosauridae reveals several differences including: the premaxilla of Iberosuchus is much taller and rostrocaudally shorter than in any known peirosaurid (i.e., Montealtosuchus, Pepesuchus desae, Peirosaurus, Uberabasuchus terrificus or Hamadasuchus rebouli) and the pattern of ornamentation differs with vermiculation versus pitted ornamentation in Peirosauridae. Also, the dentition of Peirosauridae is conical to sub-conical in cross section but is never extremely compressed, unlike in the maxilla of Iberosuchus. Iberosuchus also differs in the morphology of the postorbital bar from any peirosaurid (e.g., Hamadasuchus rebouli in [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF] because it is not even slightly inset but flushes along the lateral ornamented surface of the jugal (Fig. 2L). Unlike any peirosaurids, Iberosuchus sp. possesses an elevated rostrum and cf. Iberosuchus shows a small number of dentary alveoli (fourteen alveoli according to [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF]. Among peirosaurids, the dentary alveolar count attains eighteen alveoli [START_REF] Larsson | Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco[END_REF]Carvalho et al., 2007;[START_REF] Campos | On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil[END_REF][START_REF] Martinelli | A new peirosaurid from the Upper Cretaceous of Argentina: Implications for specimens referred to Peirosaurus torminni Price (Crocodyliformes: Peirosauridae)[END_REF].

As for postcranial elements, osteoderms have recently been reported in the peirosaurid Montealtosuchus arrudacamposi. Such osteoderms are unlike those described for Iberosuchus in presenting a quadrangular outline and an external ornamentation with cupules [START_REF] Tavares | Osteoderms of Montealtosuchus arrudacamposi (Crocodyliformes, Peirosauridae) from the Turonian-Santonian (Upper Cretaceous) of Bauru Basin, Brazil[END_REF]. Therefore, no characters support an affinity of Iberosuchus with the Peirosauridae.

Iberosuchus resembles the Baurusuchidae in sharing the elevation of the rostrum, a vermiculate ornamentation, mediolaterally compressed maxillary teeth, an enlarged third maxillary alveolus and dentary dentition, a vermiculate pattern of ornamentation and osteoderms with a tall ridge and a rugose aspect. An autapomorphy of the Baurusuchidae is the extreme reduction of the number of premaxillary and maxillary alveoli (e.g., Montelfreto et al., 2010;[START_REF] Riff | Baurusuchid crocodyliforms as theropod mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti (Upper Cretaceous of Brazil)[END_REF]. In Iberosuchus, the presence of five premaxillary alveoli, more than five alveoli in the maxilla and a premaxillary palatal foramen discard a referral to the Baurusuchidae or to Bretesuchus bonapartei [START_REF] Gasparini | New tertiary sebecosuchians (Crocodylomorpha) from South America: phylogenetic implications[END_REF]. Pabwehshi pakistanensis has been tentatively allied to the Baurusuchidae [START_REF] Wilson | New crocodyliform (Reptilia, Mesoeucrocodylia) from the Upper Cretaceous Pab Formation of Vitakri, Balochistan (Pakistan)[END_REF] and is comparable to Iberosuchus in sharing a palatal foramen at the level of the premaxillarymaxillary suture, the morphology of the perinarial fossa, the elevated rostrum and the notch for reception of an enlarged dentary tooth. As with Iberosuchus or Bergisuchus, the affinities of Pabwehshi pakistanensis are only tentative because of the fragmentary nature of the material. However, the premaxillary tooth count and maxillary alveolar size precludes further affinities of Iberosuchus with Pabwehshi pakistanensis. The morphology of the postorbital bar in the baurusuchid Pissarachampsa serra is different from Iberosuchus macrodon from Aldealengua, Spain (Ortega, 2004 unpublished) and from Iberosuchus sp. from Aumelas (Fig. 2G-K) in being slightly inset (Montefeltro et al., 2011). Although evidence to ally Iberosuchus to the Baurusuchidae on the basis of cranial elements is not supported, [START_REF] Martin | A sebecosuchian in a middle Eocene karst with comments on the dorsal shield in Crocodylomorpha[END_REF] highlighted the morphological similarity of European sebecosuchian osteoderms with those of Baurusuchus [START_REF] Nascimento | A new species of Baurusuchus (Crocodyliformes, Mesoeucrocodylia) from the Upper Cretaceous of Brazil, with the first complete postcranial skeleton described for the family Baurusuchidae[END_REF][START_REF] De Araújo Júnior | Taphonomy of a Baurusuchus (Crocodyliformes, Baurusuchidae) from the Adamantina Formation (Upper Cretaceous, Bauru Basin), Brazil: implications for preservational modes, time resolution and paleoecology[END_REF]. Nevertheless, osteoderms have not been reported in the Sebecidae and similar osteoderms do also exist in non-sebecosuchian notosuchians, which may indicate that this morphology might be widespread within Notosuchia [START_REF] Martin | A sebecosuchian in a middle Eocene karst with comments on the dorsal shield in Crocodylomorpha[END_REF].

With the Sebecidae, Iberosuchus shares a vermiculate ornamentation, a vertical maxilla, an enlarged third maxillary alveolus, strongly compressed ziphodont teeth as well as characters exclusively found in the Sebecidae. The premaxilla of Iberosuchus, Lorosuchus nodosus and Sebecus icaeorhinus bear subconical premaxillary alveoli matching the subcircular outline of the opposing dentary alveoli [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF][START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF]. The dentary is unknown in Ayllusuchus fernandezi but the premaxillary alveoli are also subcircular (fig. 2 in Gasparini, 1984). The postorbital bar of Iberosuchus is similar to that of Sebecus icaeorhinus (fig. 7 in [START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF] in presenting a vertical postorbital bar that is almost in line with the ornamented lateral surface of the bone. The postorbital bar of Lorosuchus nodosus has a similar position but unlike Iberosuchus macrodon or Sebecus icaeorhinus, it is ornamented at its base [START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF]. The area of interest is not preserved in Ayllusuchus fernandezi, Zulmasuchus querejazus, Barinasuchus arveloi or Langstonia huilensis. Although the remains from Languedoc do not preserve a frontal, [START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF] noted that a sagittal crest is present on the dorsal surface of the frontal of Iberosuchus, as in sebecids [START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF]. Finally, the only difference to be detected is the premaxillary alveolar count, which is smaller in Ayllusuchus fernandezi, Barinasuchus arveloi, Langstonia huilensis, Lorosuchus nodosus and Sebecus icaeorhinus all possessing four premaxillary alveoli [START_REF] Gasparini | New tertiary Sebecosuchia (Crocodylia: Mesosuchia) from Argentina[END_REF][START_REF] Paolillo | Nuevos cocodrilos Sebecosuchia del Cenozoico suramericano (Mesosuchia: Crocodylia)[END_REF][START_REF] Langston | Ziphodont crocodiles: Pristichampsus vorax (Troxell), new combination, from the Eocene of North America[END_REF][START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF][START_REF] Colbert | Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia[END_REF] versus five alveoli for Iberosuchus.

The relationships of Iberosuchus with other non-eusuchian ziphodont mesoeucrocodylians remain unsolved and more complete material is needed to allow testing a proper phylogenetic hypothesis. Nevertheless, limited clues available from the fragmentary specimens discovered from southern France hint at a possible affinity with the Sebecidae. This is in good agreement with previous phylogenetic results that recovered Iberosuchus and Bergisuchus as non-sebecid sebecosuchians (i.e., more derived than Baurusuchidae and close to the Sebecidae) (e.g. [START_REF] Rossmann | Studies on Cenozoic crocodiles: 8. Bergisuchus dietrichbergi Kuhn (Sebecosuchia: Bergisuchidae n. fam.) from the Middle Eocene of Germany, some new systematic and biological conclusions[END_REF][START_REF] Pol | A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina[END_REF][START_REF] Kellner | A new sebecid from the Paleogene of Brazil and the crocodyliform radiation after the K-Pg boundary[END_REF][START_REF] Pol | A new notosuchian from the Late Cretaceous of Brazil and the phylogeny of advanced notosuchians[END_REF]. The quality of the European material is at the moment insufficient to clarify previous questions on the biogeographic origin of Iberosuchus (Buffetaut, 1982a;1986;[START_REF] Buffetaut | A ziphodont mesosuchian crocodile from the Eocene of Algeria[END_REF]. This matter could be further refined with a detailed update on Iberosuchus remains from Spain [START_REF] Ortega | El cocodrilo de El Viso (Eoceno, Zamora): consideraciones acerca de los «zifodontos» (Metasuchia,?Sebecosuchia) del Eoceno de la cuenca del Duero[END_REF][START_REF] Ortega | Historia evolutiva de los cocodrilos Mesoeucrocodylia[END_REF], with future discoveries from other European localities or from Paleogene deposits of North Africa, where another poorly known taxon with a ziphodont dentition, Eremosuchus elkoholicus was described (Buffetaut, 1982b;[START_REF] Buffetaut | A ziphodont mesosuchian crocodile from the Eocene of Algeria[END_REF]. Aumelas, Saint-Martin-de-Londres, Hérault, and Robiac, Gard (this paper); and La Livinière, Hérault [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF] and Issel, Aude [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF]. [planned for column page width] et La Livinière, Hérault [START_REF] Buffetaut | Un mésosuchien ziphodonte dans l'Eocène supérieur de la Livinière (Hérault, France)[END_REF] et Issel, Aude [START_REF] Ortega | Reinterpretation and new denomination of Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)[END_REF].

Fig. 1 .

 1 Figure captions.

Fig. 1 .

 1 Fig. 1. Carte du sud de la France montrant les localités (étoiles) ayant fournies les restes

Fig. 2 .

 2 Fig. 2. Skull remains of Iberosuchus sp. from the Lutetian of Aumelas, Hérault, France. Right

Fig. 2 .

 2 Fig. 2. Restes crâniens d'Iberosuchus sp. du Lutétien d'Aumelas, Hérault, France.

Fig. 3 .

 3 Fig. 3. Skull remains of Iberosuchus sp. from the Lutetian-Bartonian of Saint-Martin-de-

Fig. 3 .

 3 Fig. 3. Restes crâniens d'Iberosuchus sp. du Lutétien-Bartonien de Saint-Martin-de-Londres,

Fig. 4 .

 4 Fig. 4. Isolated tooth of Iberosuchus sp. (SMF 206) from the Lutetian-Bartonian of Saint-

Fig. 3 .

 3 Fig. 3. Dent isolée d'Iberosuchus sp. (SMF 206) du Lutétien-Bartonien de Saint-Martin-de-

Fig. 5 .Fig. 5 .

 55 Fig. 5. Details of the dentition of Iberosuchus sp. from the Lutetian of Aumelas, Hérault,

Fig. 6 .

 6 Fig. 6. Osteoderms attributed to Iberosuchus sp.. A-D (RBN 2019; E-H: RBN 2021; I-L:

Fig. 6 .

 6 Fig. 6. Ostéodermes attribués à Iberosuchus sp.; les cinq premiers proviennent du Bartonien

Acknowledgments

B. Marandat and S. Jiquel provided access to the palaeontology collections at ISEM; A-L.

Charruault prepared some of the material presented in this article and several persons from the laboratory contributed to making my visit in 2012 enjoyable and fruitful.


B Thiria

O Cadot

J.-F Beaudoin

Drag fluctuations of a disk in a turbulent jet: Effect of turbulent scales averaging

The drag fluctuations of a disk placed on the axis of a turbulent incompressible jet are studied at Re = 70000. Statistics and spectra have been obtained for different disk sizes. A significant spatial averaging effect is observed in the symmetrization of probability distribution function and in the low-pass filtering of spectra. These effects are associated with a redistribution of the high-frequencies energy to the low frequencies. It is shown that this redistribution is done in such a way that the rms value of the drag fluctuations increases linearly with the disk surface. These results concerning the drag fluctuations are compared and found to be consistent with fluctuations of a global kinetic energy extracted from the turbulent field in front of the disk.

Introduction. -Fluctuations of global quantities in out-of-equilibrium systems are of general interest. For the last ten years, a global quantity as the power injected in a closed turbulent flow has been thoroughly studied [1][2][3][4][5][6][7]. The fluctuations are not symmetric [1,8] but tend to symmetrize as the degrees of freedom are increased [5,8,9]. In the closed flow, the number of degrees of freedom strongly depends on the aspect ratio of the experiment that determines the number of large-scale structures [5,9]. Hence, the central limit theorem, implying a symmetrization of the fluctuations together with a reduction of the fluctuation rate as the number of degrees of freedom is increased is satisfactorily verified [5].

There are far fewer experimental results concerning the case of open turbulent flows which are also of general interest for direct industrial applications. For instance, questions of practical importance are: how do the global force fluctuations exerted on a body under turbulent conditions behave with different body sizes and flow characteristics? Is there a smoothing effect of the fluctuations due to a spatial averaging of the turbulent scales? Is the central (a) Present address: Physique et Mécanique des Milieux Hétérogènes (PMMH) UMR 7636 CNRS ESPCI P6 P7 -10 rue Vauquelin, F-75231, Paris Cedex 5, France, EU; E-mail: bthiria@pmmh.espci.fr limit theorem relevant for this case? For open turbulent flows, we are actually only aware of the work of Ciliberto et al. [10] who considered the drag fluctuations of a disk placed in a fully turbulent jet. The authors were studying the temporal averaging of the drag fluctuations in order to bring some experimental evidence of the Gallavotti-Cohen fluctuation theorem (see references in [10]). This theorem predicts the ratio of the probabilities for positive-and negative-energy injection rates (a quantity related to the instantaneous drag) averaged over a variable time window. In order to observe negative events of drag (an essential ingredient for the fluctuation theorem), the authors placed the disk in a very specific region, not on the axis of the turbulent jet where the instantaneous drag is always positive (as we will do in this work), but sufficiently far from the axis to obtain some negative drag events. While the work of Ciliberto et al. [10] was a temporal averaging study, the goal of the present work is a spatial averaging study of the turbulent scales impacting on the disk surface.

We considered two cases in a turbulent jet flow at a fixed Reynolds number. In the first case, the global quantity is directly the drag that the turbulent jet exerts on a disk of diameter D. In the second case, the global quantity is a kinetic energy contained in a square area in front of the disk. The aim of this work is to study effects of the spatial averaging of the turbulent scales on the drag fluctuations of the disk. The question we address is: what are the properties of these drag fluctuations as the disk size increases?

Experimental setup. -The turbulent air jet is formed by a nozzle of 20 mm in diameter. We used five disks having diameters of 10 mm, 15 mm, 22 mm, 30 mm and 40 mm. Each disk was successively placed one meter from the nozzle, centred on the jet axis and perpendicular to it (fig. 1). At this location and without disk, the freejet width is δ = 110 mm, the mean velocity taken on the jet axis is u = 10 m • s -1 , the fluctuation rate defined as urms u is 28%, and the corresponding Reynolds number based on the jet width is Re = u δ ν ∼ 70000. At this location, the different characteristic scales of the jet are the integral scale L ∼ 55 mm (based on the jet's half-width), the Taylor micro-scale λ ∼ 3.5 mm and the Kolmogorov scale η ∼ 0.1 mm. All the disks we use are smaller than the integral scale of the flow and much larger than either the dissipative scale or the Taylor micro-scale.

Force fluctuations are performed using a highly sensitive quartz force sensor of type 9203 from Kistler measuring compressive force from few mN to 500 N. The sensor is mounted on the disk in order to be sensitive to the force component that is parallel to the main flow direction u. This component corresponds to the drag exerted on the disk (see fig. 1). As we need a high-resolution frequency of the drag fluctuations, particular attention has been given to the measurement itself. Indeed, fluctuations of drag are so weak especially at high frequencies, that any vibrations of the mechanical structure of the sensor support will considerably mask the true aerodynamic drag. Many different materials were tried for the holding stand until the force sensor was directly placed on a block of dough whose property is to be exclusively plastic (non-elastic) and the disk was stuck to the force sensor with bee wax. There is no screw, no mechanical articulation in our system. This special setup has allowed us to push away all the resonances, which of course still exist, as far as we can. From this particular setup, the frequency response is directly measured using an electric coil supplied with a white noise current and placed in front of the disk. The random electromagnetic force suffered by the magnet is then compared to the initial white noise excitation. Figure 2(a) displays the frequency response obtained with the disk of diameter D = 40 mm. From this result, we can obtain reliable measurements of the force fluctuations up to 1200 Hz. For comparison in the work [10], it is the response of a flexion that is measured and the cut-off is much lower about 30 Hz. On the other hand, our transducer is not sensitive to the low-frequency fluctuations, the corresponding high-pass filtering is about 10 Hz. In the following, we shall call δF (t) the drag fluctuations.

A hot-wire probe is used to obtain a local kinetic energy. The measurement point is localized on the jet axis, 10 mm upstream from the disk as displayed in fig. 1(a). The hot wire is always removed when drag is measured to avoid any contaminations. The hot wire is placed in such a way to be sensitive to u(t) 2 + v(t) 2 which is the modulus of the velocity projected in a plane containing the jet axis and the measurement point. We denote by (t) = 1 2 (u(t) 2 + v(t) 2 ) the quantity corresponding to a local kinetic energy and by δ (t) its fluctuation about the mean.

Finally, we perform Particle Image Velocimetry measurements (using a LAVISION PIV setup) to extract the instantaneous velocity field whose components are u and v (fig. 1(b)). The light sheet is produced by two lasers Nd : Yag of 50 mJ per pulse. A 12-bit camera with a CCD resolution of 1200 × 1600 is used. The seeding is insured by an olive oil spray placed at the entrance of the fan that generates the jet. The measurements area covered by the camera field is 80 mm × 60 mm and the corresponding image resolution is 0.05 mm per pixel. For the inter-correlation postprocessing of the images, we use interrogation windows of 16 pixels × 16 pixels. The resolution for the velocity measurements is then 0.8 mm. The square area of dimensions D × D denoted as the "averaged area" in fig. 1(b) is the surface on which spatial averaging will be performed (see later in the text). In the following, symbols . . . denotes temporal averaging. During a PIV acquisition, the sampling frequency of the velocity field is not constant in time and may fluctuate between 3 Hz and 10 Hz. The PIV setup does not solve the dynamic of the large-scale structures since their typical turnover time is about L U ≈ 0.05 s. Temporal statistics are performed over 2000 velocity fields that can reasonably be assumed as independent.

Results. -We first use the smallest disk (D = 10 mm). We measure the fluctuating drag, δF (t) and the local velocity with the hot wire u(t) 2 + v(t) 2 located upstream from the disk (see fig. 1(a)). Figure 2(b) shows the comparison between power spectra of the local velocity (which correspond to a kinetic-energy spectrum) and drag measurements. The kinetic-energy spectrum falls as the classical f -5/3 law as expected in the Kolmogorov theory. The power spectrum of the drag fluctuations is very similar to that of the local kinetic-energy spectrum in the range of the low frequencies. A different behavior is observed for the high-frequencies range where the drag fluctuation power spectrum decreases more abruptly than the kinetic-energy spectrum.

In fig. 3, the Probability density function (Pdf) of the reduced drag fluctuation δF obtained for the smallest disk D = 10 mm is compared to the Pdf of the local kineticenergy fluctuations δ measured from the local velocity probe. Both Pdfs are also very similar, especially the tail for positive events that superimposes satisfactorily. The Pdf asymmetry of the kinetic energy is at first order a consequence of the quadratic non-linear deformation of the velocity Pdf which is mainly Gaussian. This is confirmed by the good superimposition on the same graph of a Chi2 distribution. Although the asymmetry sign is in agreement with the previous result of Ciliberto et al. [10] for drag statistics, we do not observe exponential tails as they do. This difference is related to the important role that plays the large-scale flow inhomogeneity: our disks are placed on the jet axis, while in Ciliberto et al. [10] the disk is placed at a distance of four disk's diameter off the jet axis. From the spectra in fig. 2(b) and the Pdfs in fig. 3, we find that the drag fluctuations behave, at first order as the fluctuations of the local kinetic energy in the jet. The result is consistent with the assumption that the drag fluctuations are simply associated with the pressure head fluctuations on the disk. In order to check this idea, we placed the disk in a uniform flow (wind tunnel of 400 mm × 400 mm in test section) having the same velocity say, 10 m/s. In this case the drag fluctuation are too small to be measurable. We then conclude that drag fluctuations due to the wake are negligible compared to that of the forehead disk when the incoming flow is the turbulent jet. We can establish a simple relationship, based on dimensional arguments, between the head pressure and the kinetic energy. For a uniform incoming incompressible fluid of velocity U , the pressure head on the disk is given by the Bernoulli's theorem, P = P 0 + 1 2 ρU 2 , with P 0 the free-stream pressure and ρ the air density. Replacing U by u(t), we obtain that the pressure head fluctuations, and hence the drag fluctuations in our case, depends on the kinetic-energy fluctuations in the bulk upstream from the disk. This is exactly what is revealed by fig. 3. Assuming that the velocity fluctuations are small compared to the mean velocity in the jet, one obtains that δP (t) ∼ ρ u δu(t). In this case, fluctuations of the local velocity are proportional to the drag fluctuations. This dimensional relation explains why we observe similar spectra in fig. 2(b). Of course Bernoulli's theorem does not hold rigorously in our case, our result only expresses a conservation law between pressure and kinetic-energy variation. In the detail the spectrum of the local velocity in fig. 2 frequencies than that of the drag fluctuations. This faster decrease is related to a spatial averaging effect. The effect is confirmed in the following when the size of the disk is increased.

(b) decreases more abruptly at high

The magnitude of the disk surface S influences the statistics of the drag fluctuations. The Pdfs of the drag in fig. 4(a) tend to symmetrize as S increases: the tail at large positive drag fluctuations is shortened while the other tail for the negative fluctuations is reinforced (this observation is displayed by arrows in fig. 4(a)). The effect is weak but very significant since the hierarchy of the tails follows the hierarchy of the disk diameters. While the Chi2 distribution represents well the Pdf for D = 10 mm (fig. 3), it becomes less and less accurate as D increases. In fig. 5(a), we plot the skewness δF 3 vs. S/S L , where S L = π( L 2 ) 2 is the characteristic surface of the integral scale impacting the disk defined from L = 55 mm, the half-width of the free jet at the disk location. We can see that the skewness decreases continuously as the disk surface increases. The spatial averaging effect is also clearly visible in fig. 4(b) that shows the evolution of the power spectra of drag fluctuations with D. Each power spectrum has been divided by the corresponding disk surface. A cut-off frequency due to the size of the integration surface shifts to lower values as D increases. As the integration surface increases, scales smaller than the integration surface naturally average and some energy at high frequencies is then lost. While more energy related to the small scales is lost as S increases, more energy is created in the large scales since the plateau at low frequencies is elevated (the effect is displayed by arrows in fig. 4(b)). On the other hand, we find that the root-meansquare (rms) value δF 2 is linear with the surface in fig. 5(b) or equivalently that δF 2 divided by the surface is almost constant in fig. 6(b) (squares). In consequence of the Parseval relation, all the spectra in fig. 4(b) have the same integral over the whole frequencies range. The spatial averaging due to the disk size does not smooth the fluctuations as it would be expected from the central limit theorem. The reason should be the interaction between the disk and the jet that is observed as a redistribution of the high-frequencies energy (small scales) to the low-frequencies energy (large scales) by keeping constant the total energy of the fluctuations per surface unit. The jet-disk interaction strongly modifies the turbulent mean flow by imposing a turbulent boundary layer on the disk. In fig. 6(a), the kinetic energy of the mean flow extracted from PIV measurements along the jet axis, 0 (0, y) = 1 2 ( u 2 + v 2 ) decreases toward zero on the disk. As shown in the inset of fig. 6(a), for every disk, the decreasing laws superimpose when y is scaled by D. The typical length scale for the turbulent boundary layer on each disk is then simply given by D.

The last global variable we have considered is extracted from the PIV measurements. It is a total kinetic energy E contained in a square area of the xy-plane whose size is equal to the disk diameter D (see fig. 1(b)) and defined as

E(t) = i,j∈D×D (u i,j (t) 2 + v i,j (t) 2 ),
where (i, j) denotes the location of the velocity vector inside the area D × D. The local velocities measured with the PIV setup already result from a spatial averaging over a square area of size δs = 0.08 mm × 0.08 mm. It corresponds to the size of the interrogation window and also to the mesh size of the location matrix. For each disk, we acquired 2000 velocity fields and then obtained 2000 realizations for E. We also perform the same velocity measurements without disk in order to characterize the averaging effect of the free jet. In this case, we also consider the five averaged areas corresponding to the five disk diameters. For each realization set of E, we computed the rate of fluctuations defined as: δErms D 2 , where δE rms = (E -E ) 2 . This quantity is plotted in fig. 6(b) vs. the surface of integration D 2 /L 2 for the free jet and jet with disks. The quantity is normalized by its magnitude for the larger area of integration, say D = 40 mm (for which D 2 /L 2 = 0.53). The free jet exhibits a pronounced averaging effect, the larger the size of integration the smaller the rms fluctuation rate.

Discussion and conclusion. -The aim of this work was to study the consequence of the spatial averaging of turbulence scales on the drag fluctuations of a disk placed in a turbulent jet. The equivalence between the local kinetic energy in front of the disk and the drag is shown with the smaller disk (D = 10 mm) by the similarities of the Pdf (fig. 3) and the spectra (fig. 4). When the disk size is increased, the rms fluctuations density of the global kinetic energy computed in an area in front of the disk behave mostly as the rms fluctuations density of the drag (fig. 6(b)). We can then assume that the drag fluctuations exerted on the disk are mainly governed by the global kinetic energy contained in an area in front of the disk. In other word, the way the drag statistics behave as the disk size D increases should be similar to that of the statistics of the global kinetic energy taken over an area of size D in front of the disk.

For the free jet, the rms density fluctuations of the global kinetic energy contained in a box decreases continuously as the size of the box increases (fig. 6(b)). This smoothing of the fluctuations is consistent with a constant correlation length, characteristic to the free jet (proportional to the large-scale length), and smaller than the box sizes. It is equivalent to an increase in the effective number of degrees of freedom as the box size is increased.

When a disk is introduced in the turbulent jet, the smoothing effect of the rms density fluctuations averaging nearly disappears (fig. 6(b)). Actually the presence of the disk in the jet modifies the turbulent flow property in front of the disk compared to that of the free jet. A new correlation length, corresponding to the boundary layer thickness on the disk is introduced. We find this length to be proportional to the disk diameter D (fig. 6(a)), which may be consistent with a constant number of degrees of freedom irrespective of the disk diameter. Although we do not observe spatial averaging effect on the rms density fluctuations of the drag, the low-pass filtering of the spectra (fig. 4(b)) and the Pdfs symmetrization (fig. 4(a)) indicate, on the other hand, a significant disk's size effect. This low-pass filtering is actually associated with a redistribution of the high-frequency energy fluctuations to the low frequencies. In conclusion, increasing the body size in a turbulent jet will not lead to a reduction of its drag fluctuation rate. The reason is that the body imposes a new correlation length proportional to its size which acts on the drag as a low-pass filter and symmetrizes the PDF, but keeps the fluctuation rate constant. * * *

Fig. 1 :

 1 Fig. 1: Experimental setup. (a) Setup for drag and local velocity measurements. (b) PIV measurements setup with the disk having the larger size D = 40 mm. The camera field dimensions are fixed, while the size of the averaged area (see text) displayed by a dashed line is adapted to the disk diameter.

Fig. 2 :

 2 Fig. 2: (a) Frequency response of the force transducer measured as explained in text while the transducer is loaded with the D = 40 mm disk. (b) Comparison of power spectra of local velocity measurement (hot wire) and drag fluctuations of the disk of diameter D = 10 mm.

Fig. 3 :

 3 Fig. 3: Comparison of the Pdf of the reduced drag fluctuations δF = δF √ (δF ) 2 obtained from the disk of diameter D = 10 mm with the Pdf of the reduced local kinetic-energy fluctuations δ = δ √ (δ ) 2 obtained from the local hot-wire measurements and a Chi2 distribution.

Fig. 4 :

 4 Fig. 4: (a) Evolution of the Pdfs of the reduced drag fluctuations δF = δF (δF ) 2 as a function of S. (b) Evolution of normalized drag spectra (each power spectrum has been divided by the corresponding disk surface) as a function of S. The arrows indicate the curves legend (see text).

Fig. 5 :

 5 Fig. 5: (a) Skewness of drag fluctuations vs. the disk surface S/SL. (b) Standard deviation vs. the disk surface S/SL. The dashed line is a linear law.

Fig. 6 :

 6 Fig. 6: (a) Kinetic energy of the mean flow on the jet axis (x = 0) vs. the distance to the disk y. Inset: same data but plotted vs. y/D. (b) Rate of fluctuations of the kinetic energy contained in a D × D area vs. D 2 /L 2 . The rate of fluctuations of the free jet (triangles) is compared to a model of correlated degrees of freedom having a correlation length of LC = 2 3 L 37 mm (continuous line, see text). The rate of fluctuations in front of the disks (circles) is compared to the density of the rms fluctuations about the mean of the drag exerted on the disk presented in fig. 5(b) (squares).

The authors would like to thank A. Noullez for fruitful discussions. This work was supported by the ANR Project No. 06-BLAN-0363-01 "HighSpeedPIV".