France Polette
email: france.polette@univ-rennes1.fr

Alexis Licht

Aude Cincotta

David J Batten

Pauline Depuydt

Didier Néraudeau

Géraldine Garcia

Xavier Valentin

Alexis Polette

Aude Licht

David J Cincotta

Pauline Batten

Alexis Licht

Palynological assemblage from the lower Cenomanian plant-bearing Lagerstätte of Jaunay-Clan-Ormeau-Saint-Denis (Vienne, western France): Stratigraphic and paleoenvironmental implications

Keywords: Palynology, palaeobotany, Anemiaceae, freshwater, Cretaceous, France

Introduction

The study of mid-Cretaceous palaeobotanical and palynological assemblages has been historically essential for our understanding of the rise to dominance of angiosperms [START_REF] Wing | Ecological aspects of the Cretaceous flowering plant radiation[END_REF]. In Europe, our knowledge of this key interval for angiosperm evolution comes from several Albian-Cenomanian fossil sites with angiosperm-rich palaeofloras and palynofloras, mostly from Czech Republic [START_REF] Pacltová | Palynological study of Angiospermae from the Peruc Formation ( ?Albian-Lower Cenomanian) of Bohemia. Sbornı ḱ geologicky ćh věd / R ̌ada P[END_REF][START_REF] Greguš | Revision of Cenomanian flora from the Maletín sandstone[END_REF][START_REF] Kvaček | Comparison of Cenomanian floras from western interior North America and Central Europe[END_REF][START_REF] Kvaček | Zlatkocarpus gen. nov., a new angiosperm reproductive structure with monocolpate-reticulate pollen from the Late Cretaceous (Cenomanian) of the Czech Republic[END_REF][START_REF] Kvaček | The Early Angiosperm Pseudoasterophyllites cretaceus from Albian-Cenomanian of Czech Republic and France Revisited[END_REF][START_REF] Kvaček | Pseudoasterophyllites cretaceus from the Cenomanian (Cretaceous) of the Czech Republic: A possible link between Chloranthaceae and Ceratophyllum[END_REF], Spain [START_REF] Gomez | Klitzschophyllites, aquatic basal Eudicots (Ranunculales?) from the Upper Albian (Lower Cretaceous) of north-eastern Spain[END_REF][START_REF] Sender | Ploufolia cerciforme gen. et comb. nov.: aquatic angiosperm leaves from the Upper Albian of north-eastern Spain[END_REF][START_REF] Sender | A new uppermost Albian flora from Teruel province, northeastern Spain[END_REF], and France (see captions of Fig. 1 for references).

In western France, numerous palaeobotanical and palynological investigations have been carried out on Cenomanian deposits since the mid-19 th Century, owing to the high abundance of quarries and coastal cliffs. The large majority of the plant macroremains have been recovered from Charente-Maritime and Maine-et-Loire as fossil wood and diverse foliage preserved as impressions or in flints, and the highest diversity of continental palynomorphs has been recorded in Charente-Maritime, Charente and Vendée (Fig. 1, see caption for references). However, very little has been published on localities yielding both plant macroand microremains, along with their potential affinities (Table 1). The rare deposits containing diversified macrofossil assemblages have so far yielded either a surprisingly poor palynoflora or none at all, such as the plant-bearing clays from the Hucheloup and the Puy-Puy quarries in Maine-et-Loire [START_REF] Pons | Les organes reproducteurs de Frenelopsis alata (K. Feistm.) Knobloch, Cheirolepidiaceae du Cénomanien de l'Anjou[END_REF][START_REF] Fleury | Palaeobotanical investigation of a Cenomanian clay lens in Hucheloup Quarry, Maine-et-Loire, NW France : Taxonomic, stratigraphic and palaeoenvironmental implications[END_REF] and Charente-Maritime respectively [START_REF] Néraudeau | Stratigraphie et paléontologie (plantes, vertébrés) de la série paralique Albien terminal-Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)[END_REF][START_REF] Peyrot | Apport de données palynologiques à la reconstruction paléoenvironnementale de l'Albo-Cénomanien des Charentes (Sud-Ouest de la France)[END_REF]; Table 1). Conversely, deposits that have yielded abundant palynomorphs rarely contain a diversified macroflora, as is the case for the majority of the Cenomanian deposits from Vendée [START_REF] Azéma | Étude palynologique préliminaire du gisement cénomanien de la Bironnière, Vendée (France)[END_REF][START_REF] Azéma | Des miospores du Cénomanien moyen[END_REF], and for Archingeay-Les Nouillers in Charente-Maritime [START_REF] Moreau | Albian flora from Archingeay-Les Nouillers (Charente-Maritime): comparison and synthesis of Cretaceous mesoand macro-remains from the Aquitaine Basin (southwestern France)[END_REF]; Table 1).

The locality of Jaunay-Clan-Ormeau-Saint-Denis (Vienne) is in this regard a notable exception. During the construction of the LGV SEA railway line in 2012 and 2014, palaeontological investigations were carried out by the team of X. Valentin in the temporarily outcropping lower Cenomanian clay deposits near the village of Jaunay-Clan (Fig. 2, Valentin et al., 2014). They described an assemblage composed of leaf impressions, various bivalves, crustacean, ichnofossils, insect body, wing impressions, and theropod feathers [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF][START_REF] Nel | New dragonflies from the early Cenomanian of France enlighten the timing of the odonatan turnover at the Early/Late Cretaceous boundary[END_REF]. The astoundingly well-preserved palaeoflora is composed of four genera of ferns, three genera of gymnosperms, and two genera of angiosperms, namely Ploufolia and Eucalyptolaurus [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF], making Jaunay-Clan Ormeau-Saint-Denis (JCO) one of the most diversified Cenomanian plant-bearing localities of France (Table 1). The Jaunay-clan locality is thus regarded as a true Lagerstätte, according to the excellent preservation and the diversity of its fossil assemblage. In contrast to the other assemblages of western France, the Jaunay-clan yielded a rich palynoflora in combination to its rich macroflora. The stratigraphic, taxonomic, and palaeoecological details of this assemblage are presented herein, in the hope of achieving a clearer understanding of this unique French Cenomanian palaeoenvironment, and more generally of the Cenomanian vegetation of western France.

Geological setting

The Jaunay-Clan area is situated about 15 km north of Poitiers, in the southwestern part of the Paris Basin, and is crossed from southeast to northwest by the Clain River (Fig. 2).

Outcropping deposits are constituted by Callovo-Oxfordian limestones unconformably overlain by lower Cenomanian deposits [START_REF] Bourgueil | Notice de la carte géologique de la France à 1/50 000[END_REF]. The contact between the Callovo-Oxfordian limestones and the lower Cenomanian deposits is marked by a ferralitic alteration surface developed on a palaeo-karst which has been eroded in places [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]. The fossiliferous deposits at Jaunay-Clan consist of 1-5 m thick deposits filling up small (~30 m wide) depressions on the post-Oxfordian surface. At the site of sampling, the JCO locality, (Fig. 3), they specifically consist of, from bottom to top:

-about 10 cm of massive reddish clay, with numerous calcareous nodules, ferruginous pisolites and cm-thick sand layers; -30 to 40 cm of clast supported, brecciated limestones and ferriginous pisolites, likely reworked from the alteration surface [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]; -about 1.20 m of calcareous mudstones interlaminated with millimetre-scale layers of finegrained sand and organic-rich mudstone, containing plant remains, worm ichnofossils, invertebrates trackway and wings, a theropod feather, crustaceans and bivalves [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF].

This sequence progressively grades into non-fossiliferous laminated grey siltstones and coarse ferruginous sand and is capped by Lower Cenomanian glauconitic sandstones that can be found regionally [START_REF] Joubert | Le Cénomanien des départements de la Vienne et des Deux-Sèvres[END_REF].

Material and Methods

3.1.Extraction method

Ten samples (JCO A-JCO D, JCO 5, JCO 6b, JCO 8, JCO 12, JCO 13, JCO 15) were collected by X. Valentin and A. Cincotta from the JCO locality and analyzed for their palynological content (Fig. 3). Samples were processed at the University of Liege following a method consisting of immersion of 25 g of sample in 15% HCl followed by digestion in 30% HF, and sieving through mesh sizes of 12 and 200 µm, washing between each stage until neutral pH.

Another sample was sent to DJB by DN in 2014, and was processed at Aberystwyth University for its microfossil (QPR3670) and mesofossil (MFP513) content, following the extraction procedure of [START_REF] Batten | Extraction techniques: small palynomorphs[END_REF] for the microfossils. The extraction of megaspores involved initial soaking of 100 g of rock in warm water on a hot plate followed by immersion of the sample in a solution of Na4P2O7 in order to disaggregate it as much as possible before sieving through a 70 mm mesh to reduce its bulk prior to standard palynological processing using HCl and HF. A few megaspores were recovered, and picked out of the aqueous residues under a stereomicroscope and housed dry in micropalaeontological slides. Some of the specimens recovered were mounted on scanning electron microscope (SEM) stubs to which carbon tabs had been fixed, and sent by DJB to FP for examination under a Phenom table

SEM.

Seven samples (JCO D, JCO 8, JCO B, JCO 12, JCO A, JCO 13, JCO 15) were shown to be particularly productive. Others are either barren (JCO C) or very poor in fossil content (QPR3670, JCO 5, JCO 6b). The fossil site being no longer exposed, it was not possible to analyze more samples from those levels.

Specimen counts

250 specimens were counted and identified in order to compare the relative abundance of the different botanical families or taxa of higher ranks (see Section 4) for samples JCO B, JCO 12, JCO A, JCO 13, JCO 15; note that all the palynomorphs present on the slides (between 506 and 4300) were counted and observed in order to note the presence of new species, and produce rarefaction curves (see Section 4). The two other productive palynological preparations, JCO D and JCO 8, yielded 241 and 163 palynomorphs respectively. Sample JCO 5 yielded 15 specimens, and samples JCO 6b and QPR3670 only yielded the freshwater algae Schizosporis reticulatus.

Rarefaction curves are the product of the relation between the cumulative specific diversity and the number of palynomorphs encountered in a sample. They were established in order to see whether the diversity of the different palynological assemblages described herein is well represented, and if they could be thoroughly compared to each other. The use of rarefaction analyses in Quaternary strata instead of more common diversity indices, such as Shannon's and Simpson's, was extensively discussed by [START_REF] Birks | The use of rarefaction analysis for estimating palynological richness from Quaternary pollen-analytical data[END_REF]. Rarefaction curves are used to estimate the observed richness of palynomorphs in a sample, and are different from other standard rarefaction analyses used to estimate the potential richness of an incomplete assemblage [START_REF] Birks | The use of rarefaction analysis for estimating palynological richness from Quaternary pollen-analytical data[END_REF]. Their purpose is not to infer an estimate of diversity, but only to observe the actual diversity of the sample; they do not require any mathematical or statistical treatment to be calculated. All the palynological preparations are housed in University of Poitiers (CVCU) under collection numbers UP/JCO log 2013 and log 2014.

Results

A taxonomic list of species encountered in the productive samples of Jaunay-Clan Ormeau-Saint-Denis is provided in Appendix 1. Authors of species that are listed in Appendix 1 are not indicated in the text.

The palynomorphs recovered from the Jaunay-Clan Ormeau-Saint-Denis (JCO) palynoflora are generally well preserved, and only a few specimens were too distorted for reliable identification. Altogether, 184 species of megaspores, spores, pollen grains, dinocysts and algae were recovered from the seven productive samples of JCO, with a specific diversity ranging from 34 to 84 species (Appendix 1). The rarefaction curves show that a plateau is usually reached between 700 and 1000 specimens when enough specimens are present, as for JCO A, JCO B, and JCO 15 (Fig. 4). However, the richest and most diversified assemblage JCO 13 reaches a plateau at 3500 specimens, a little more than 60% of the entire specific diversity being recovered at 1000 specimens (Fig. 4). The other assemblages (JCO D, JCO 8, JCO 12) were not rich enough to reach a plateau, but the slopes of their lines are similar to those of JCO A and JCO B, except for JCO D, which is steeper. Thus, the comparative specific diversity of those three assemblages has to be considered cautiously (Fig. 5A2).

Spores are the most diversified group with 103 species of bryophyte (Pl. I.I-I.N), lycophyte (Pl. I.O-T; Pl. II.A-II.Q), and filicophyte (Pls. IIR-VH) related forms (Fig. 5A3; see Appendix 2 for botanical affinities of palynological genera). Gymnosperm pollen spectrum is composed of 33 species (Pls. V.I-V.Q, VI.T), and is taxonomically dominated by bisaccate pollen grains related to Pinaceae and Podocarpaceae (Appendix 1; Fig. 5C2). Angiosperms (Pls. VI.R, VI.S, VII.A-VII.R) are represented by 31 species of Chloranthaceae, ?Chloranthaceae/?Ceratophyllaceae , probable monocots or more basal angiosperms, eudicots, and angiosperms of uncertain botanical affinities (Appendix 1; Fig. 5D2). They are taxonomically dominated by the eudicots (Appendix 1; Fig. 5D2). Two palynological intervals can be inferred from the relative abundance of the different taxa (Fig. 5A1-D1).

JCO D-JCO 8: spore dominated assemblages

The oldest assemblages are characterized by the numerical dominance of spores, representing more between 60% and 70% of the whole assemblages (Fig. 5A1). They are dominated by forms belonging to the Gleicheniaceae (20-25%), ascribed to the genera Gleicheniidites (Pl. VII.P-VII.R). One species, identified as Nyssapollenites albertensis (Pl. VII.D) was recovered from JCO D, but is absent from the younger assemblages. Angiosperm pollen grains always represent less than 10% of the whole assemblage (Fig. 5A1). Dinoflagellates are absent, and only a few fresh water algae have been recovered (Appendix 1). These two assemblages are overall less diverse than the younger ones (Fig. 5A2), but this difference cannot be taken into account because their potential maximum diversity has not been reached (Fig. 4).

JCO B-JCO 15: pollen dominated assemblages

An abrupt change of the general composition of the palynoflora is observed from JCO B onward. While still taxonomically dominated by spores, the abundance of gymnosperm pollen grains rises significantly, representing between 50% and 70% of the whole assemblages (Fig.

5A1, 5A2

). A great increase of the abundance of Classopollis (Cheirolepidiaceae) is observed, representing from less than 10% in the oldest assemblages to 40-50% of the whole assemblages from JCO B onward (Fig. 5C1). The pollen grains of Araucariaceae and Cupressaceae (including Taxodiaceae) become more diversified, with the appearance of Callialasporites dampieri (Pl. VI.D) and Uesuguipollenites callosus (Pl. VI.F) in JCO 13 and JCO 15, and Perinopollenites halonatus (Pl. VI.I) and Taxodiaceaepollenites hiatus (Pl. VI.J) from JCO B to JCO 15 (Appendix 1; Fig. 5C2). Several species of Podocarpidites (Pl. V.Q), Cerebropollenites (Pl. VI.E), and Cedripites (Pl. V.M) also appear in this interval, along with representatives of the genus Alisporites, of uncertain gymnosperm botanical affinities (Pl.

V.K, V.L).

Along with the increasing abundance of gymnosperm pollen grains, the spore content significantly declines in comparison with the first interval, representing between 25% and 40% of the assemblages. However, the distribution of the different botanical groups stays fairly similar to that of the first interval (Fig. 5B1); only a slight decrease in the abundance of Cyatheales (ca. 5%) and Anemiaceae (ca. 2,5%) is noted (Fig. 5B1). Spores are still the most diversified group, represented by 20 to 45 species for each assemblage of JCO B-JCO 15 (Fig. 5A2,5B2). Several genera appear in this interval, namely Cingutriletes, Stereisporites Only few angiosperm pollen grains (Pl. VI.O-VI.T; Pl. VII.A-VII.R) were encountered, almost always representing less than 10% of the whole assemblages, except in the youngest assemblage JCO 15, in which 12% of the assemblage consists of angiosperm grains (Fig. 5A1). The assemblages JCO A and JCO 13 are the most diversified, with 12 and 16 species recovered respectively, mostly represented by eudicots for JCO 13 (Fig. 5D2).

Representatives of the genus Stellatopollis (monocots or more basal angiosperms; Pl. VI.R, VI.S) were only encountered in this interval. In addition, grains of Dichastopollenites (Pl. VII.P-VII.R), of uncertain botanical affinity, become more diversified and better represented than in the first interval (Ap; Fig. 5D2). The effective abundance of the angiosperms (Fig. 5D1) shows that ?Chloranthaceae/ ?Ceratophyllaceae content declines while the tricolpate forms belonging to the eudicots are progressively better represented. The abundance of the monosulcate grains linked to probable monocots or more basal angiosperms (Pl. VI.O-VI.S) is variable (Fig. 5D1). A diversification of eudicot content is also visible along the succession, with six out of 14 species encountered only in the JCO 13 and JCO 15 assemblages (Table 1).

Several species belonging to

Discussion

Biostratigraphic implications

The sedimentary sequence of Jaunay-Clan is part of a formation that has been dated to the lower Cenomanian [START_REF] Louail | Stratigraphie du Cénomanien littoral de la marge Sud-Ouest du Bassin de Paris. L'exemple du sondage de Loudun[END_REF][START_REF] Alvarez | le Cénomanien et le Turonien au NW de Poitiers (Vienne). Stratigraphie, sédimentologie, cartographie et hydrogéologie[END_REF][START_REF] Joubert | Le Cénomanien des départements de la Vienne et des Deux-Sèvres[END_REF][START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF], notably based on the presence of Acompsoceras essendiense in an hardground layer overlying the glauconious sandstones, indicative of uppermost lower Cenomanian or lowermost middle Cenomanian in Normandy and Sarthe [START_REF] Louail | Stratigraphie du Cénomanien littoral de la marge Sud-Ouest du Bassin de Paris. L'exemple du sondage de Loudun[END_REF]. However, the Jaunay-Clan locality, located below these glauconious sandstones, has never been properly dated and could be older; moreover, no this upper Cenomanian biostratigraphic age has never been tested in the light of dinoflagellate and palynomorph assemblages.

Most of the dinoflagellates recovered from the the JCO locality are relatively long-ranging species, thus not biostratigraphically informative. For example, Spiniferites ramosus is often the dominant form in Early Cretaceous assemblages, ranging from the early Valanginian to at least the Campanian. Surculosphaeridium longifurcatum, which is the dominant form in the JCO assemblage, ranges from the Early Cretaceous to the Santonian [START_REF] Costa | Dinoflagellate cysts of the Cretaceous System[END_REF], and Achomosphaera ramulifera, while mostly encountered from Cenomanian onward, has been recorded several times in Aptian-Albian deposits of the Paris Basin [START_REF] Davey | An investigation of microplankton assemblages from the Albian of the Paris Basin[END_REF][START_REF] Fauconnier | Répartition des péridiniens de l'Albien du bassin de Paris. Rôle stratigraphique et liaison avec le cadre sédimentologique[END_REF]. However, the presence of Tehamadinium coummia and Trichodinium spinosum agrees with an age of deposition no younger than early Cenomanian.

They both are usually encountered in Lower Cretaceous deposits, mostly Albian, but the presence of one or the other has been noted in lower Cenomanian deposits of Charente-Maritime [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF] and Alberta [START_REF] Bloch | Sedimentology, micropaleontology, geochemistry and hydrocarbon potential of shale from the Cretaceous Lower Colorado Group in Western Canada[END_REF].

The continental palynomorphs include Tricolpites nemejcii, which is a fairly common form in the JCO palynoflora, and is considered to appear during the early Cenomanian [START_REF] Doyle | Angiosperm pollen zonation of the continental Cretaceous of the Atlantic Coastal Plain and its application to deep wells in the Salisbury Embayment[END_REF][START_REF] Hochuli | Timing of early angiosperm radiation: recalibrating the classical succession[END_REF]. Less abundant tricolpate forms include Nyssapollenites albertensis, which is not known until the uppermost Albian [START_REF] Singh | Lower Cretaceous Microfloras of the Peace River area, Northwestern Alberta[END_REF]

, and

Retitricolporites decorosus, which has only been recorded in Cenomanian strata of North America [START_REF] Singh | Cenomanian microfloras of the Peace River area, northwestern Alberta[END_REF][START_REF] Lupia | Discordant Morphological Disparity and Taxonomic Diversity during the Cretaceous Angiosperm Radiation: North American Pollen Record[END_REF]. Microreticulatiporites sacalii has been suggested as a stratigraphic marker of the upper Albian-Cenomanian in northern America and Europe [START_REF] Ravn | Microreticulatisporites sacalii (Deák and Combaz) n. comb., a stratigraphically significant miospore from the Cenomanian of the United States[END_REF], but Ludvingson et al. (2010) indicate that this species seems to be restricted to Cenomanian strata of Nebraska. In France, this species has been almost exclusively encountered in Cenomanian deposits [START_REF] Deák | Microfossiles organiques" du Wealdien et du Cénomanien dans un sondage de Charente-Maritime[END_REF][START_REF] Azéma | Étude palynologique préliminaire du gisement cénomanien de la Bironnière, Vendée (France)[END_REF][START_REF] Médus | Le Cénomanien supérieur de la coupe de Laudun (Gard, France): étude palynologique et données sédimentologiques[END_REF][START_REF] Peyrot | Apport de données palynologiques à la reconstruction paléoenvironnementale de l'Albo-Cénomanien des Charentes (Sud-Ouest de la France)[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF], but has also been encountered in deposits considered as latest Albian in Charente-Maritime [START_REF] Dejax | Analyse palynologique de l'argile lignitifère à ambre de l'Albien terminal d'Archingeay (Charente-Maritime, France)[END_REF]. Elsewhere, this species is also very common in Cenomanian deposits but has been recorded in upper Albian deposits in Hungary and Wyoming [START_REF] Juhász | Lycopodiaceae spores from Lower Cretaceous deposits of Hungary[END_REF]Ravn, 1995). The common presence of M. sacalii and M. urkuticus at Jaunay-Clan would rather suggest an early Cenomanian rather than an upper Albian age. The absence of Normapolles is worth being noted, as this group does not appear before the mid-Cenomanian in France [START_REF] Azéma | Des miospores du Cénomanien moyen[END_REF].

Thus, the presence of Tehamadinium coummia, Trichodinium spinosum, Tricolpites nemejcii, Retitricolporites decorosus, and common Microreticulatiporites sacalii, coupled with the absence of Normapolles pollen grains suggests that the Jaunay-Clan assemblage is no older nor younger than lower Cenomanian, corroborating the previous age determination of the deposits. In addition, this assemblage is more similar to the assemblages recovered from the B1-B2 lithological subunits of Charente-Maritime and Charente than the slightly oldest ones recovered from the A1-A2 lithological subunits (see Section 5.4. for further explanation). It could be possible that the Jaunay-Clan strata were deposited simultaneously with the clay levels of the subunits B1 or B2 (mid-lower Cenomanian) described in Charente-Maritime (for further details concerning the Cenomanian lithological units, see Moreau, 1993a-b, and[START_REF] Néraudeau | Variation in echinoid biodiversity during the Cenomanian-early Turonian transgressive episode in Charentes[END_REF].

Palaeoenvironmental reconstruction

The first palynological interval (JCO D to JCO 8) described here-above is characterized by the numerical and taxonomical dominance of fern spores. The majority of extant ferns flourishes in wet conditions, and are generally used as indicators of humid settings. The high spore content likely represents the local vegetation: being generally heavier than pollen grains, spores tend to be dispersed less widely, commonly being deposited close to their producers [START_REF] Ferguson | Plant part processing and community reconstruction[END_REF]. This is supported by the several well-preserved fern macroremains recovered in the lower part of the succession [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]Fig. 3).

Other plant remains, such as the Nympheales-related Ploufolia, were only recovered from clay layers situated below the conglomerate layer rich in limestone breccias and reworked pisolites, corresponding to the first palynological interval [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]. The outstanding preservation of these freshwater taxa suggests a calm depositional environment, which can be associated with a lacustrine-type environment [START_REF] Sender | Ploufolia cerciforme gen. et comb. nov.: aquatic angiosperm leaves from the Upper Albian of north-eastern Spain[END_REF]. The presence of the megaspore Arcellites, ascribed to the Marsileaceae, supports the hypothesis of a calm freshwater environment, modern Marsileaceae being water ferns, growing in seasonally wet or aquatic habitats [START_REF] Zavialova | Species of the water-fern megaspore genus Molaspora from a Cenomanian deposit in western France: occurrence, sporoderm ultrastructure and evolutionary relationships[END_REF]Appendix 2). Dominant fern spores belong to Cyatheales, Gleicheniaceae and Anemiaceae families.

Modern Cyatheales are concentrated at the tropics, but can occupy varied habitats (Kramer in [START_REF] Kramer | The Families and Genera of Vascular Plants. I. Pteridophytes and Gymnosperms[END_REF]; Appendix 2). Their high abundance at Jaunay-Clan agrees with a globally warm mid-Cretaceous climate [START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) mid-latitude vegetation and climate dynamics on spore-pollen assemblages[END_REF]. The dominance of Gleicheniidites is fairly common in Lower and mid-Cretaceous continental deposits of Western Europe, and has already been noted several times in France [START_REF] Herngreen | Palynology of a Wealden section (Lower Cretaceous) in the "Carrière de Longueville", the Boulonnais (France)[END_REF][START_REF] Peyrot | Apport de données palynologiques à la reconstruction paléoenvironnementale de l'Albo-Cénomanien des Charentes (Sud-Ouest de la France)[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF].

Modern Gleicheniaceae are considered as opportunistic, pioneering tropical to subtropical plants, adapted to long droughts, growing in unstable habitats including dry forests and wetlands that occasionally dry out [START_REF] Coiffard | Early Cretaceous angiosperm invasion of Western Europe and major environmental changes[END_REF][START_REF] Mehltreter | Fern ecology[END_REF][START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) mid-latitude vegetation and climate dynamics on spore-pollen assemblages[END_REF]Appendix 2). Representatives of the Anemiceae usually develop under warm and humid environments, and their Mesozoic relatives may have grown along riverbanks, or as understorey in forests [START_REF] Dettmann | Spore morphology of Anemia, Mohria, and Ceratopteris (Filicales)[END_REF][START_REF] Van Konijnenburg-Van Cittert | Ecology of some Late Triassic to Early Cretaceous ferns in Eurasia[END_REF].

However, some species of Anemiceae are adapted to more arid conditions, such as found in heathlands, and may tolerate partial desiccation [START_REF] Proctor | Poikilohydry and homoihydry: antithesis or spectrum of possibilities?[END_REF][START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF] Appendix 2).

Owing to their high dispersal potential, the relatively high content of bisaccate pollen grains is not necessarily informative regarding the local depositional environment, but they can provide valuable information about general palaeoenvironmental settings. Bisaccate pollen grains from the first interval are mostly represented by Podocarpaceae, Pinaceae being absent.

Modern Podocarpaceae usually grow on mountain areas of tropical to subtropical regions, with a preference for humid settings [START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF][START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) mid-latitude vegetation and climate dynamics on spore-pollen assemblages[END_REF]Appendix 2). The presence of Vitreisporites, recovered from the JCO B assemblage, corroborates the prevalence of humid conditions, as inferred by [START_REF] Abbink | A sporomorph ecogroup model for the Northwest European Jurassic-Lower Cretaceous : concept and framework[END_REF], who suggested that this member of the Caytoniales group may have grown on the transition between floodplain and backswamp peats under warm conditions (Appendix 2).

The palaeocology of the mid-Cretaceous angiosperms from Western Europe has been extensively discussed by [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. Based on the wide range of possible habitats of Cretaceous representatives of Lauraceae (e.g. Ecalyptaulorus depreii, abundantly found at Jaunay-Clan) and Chloranthaceae (e.g. Clavatipollenites), they conclude that Cenomanian angiospermous assemblages could have developed within several types of plant communities, including aquatic, frequently disturbed and more stable hygrophilous and xerophilous associations.

Thus, the macropalaeontological and palynological information covering the lower palynological interval of the Jaunay-Clan succession suggest that the depositional settings were likely to have occurred in a calm freshwater environment, potentially submitted to occasional droughts, such as a floodplain or a pond, where abundant ferns and a few aquatic and terrestrial angiosperms could have grown along the banks under warm and relatively humid general conditions.

The upper palynological interval (JCO B to JCO 15) is largely dominated by gymnosperm pollen grains. The composition of the assemblages indicates an abrupt palaeoenvironmental change, highlighted by the marked increase of grains belonging to Classopollis, along with the appearance of dinocysts. Classopollis were produced by the extinct members of the Cheirolepidiaceae family. Members of the Cheirolepidiaceae can develop in a wide range of habitats, but are mostly associated with arid low-lying water margins environments under subtropical or tropical climate [START_REF] Alvin | Cheirolepidiaceae: Biology, structure and paleoecology[END_REF][START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF]Appendix 2). Numerous cheirolepidaceous macroremains display xeromorphic adaptations which have been interpreted to reflect dry and/or saline environments [START_REF] Pons | Paléoclimatologie comparée de deux gisements du Crétacé supérieur d'Europe occidentale[END_REF][START_REF] Mendes | Reassessment of the cheirolepidiaceous conifer Frenelopsis teixeirae Alvin et Pais from the Early Cretaceous (Hauterivian) of Portugal and palaeoenvironmental considerations[END_REF]. This sudden increase is associated with the appearance and progressive increase of dinocysts from JCO B onward, which would suggest an opening to very occasional marine inputs, the dinocysts only representing less than 2% of the assemblages. The macrofossils recovered from the Jaunay-Clan succession show a similar trend, with only well-preserved angiosperm leaves and fern fronds at the base of the succession, and the progressive appearance of more brackish organisms such as the bivalve Brachidontes sp., and various worm traces from JCO 8 onward [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]Fig. 3).

The recovery of a few specimens of Densoisporites in the youngest assemblages, along with the slight increase of the abundance and diversity of Alisporites grains could infer the existence of a distant tidally-influenced habitat [START_REF] Abbink | A sporomorph ecogroup model for the Northwest European Jurassic-Lower Cretaceous : concept and framework[END_REF]Appendices 1, 2). However, too few grains were encountered to consider this observation as a strong palaeoenvironmental argument. The appearance of several species of inaperturate pollen grains, including Taxodiaceaepollenites hiatus, Perinopollenites halonatus and araucariaceous related forms (Appendix 1) suggests the existence of conifer forests linked to wet lowlands, such as in low salinity back-swamp environments, based on the ecological requirement of some modern Cupressaceae [START_REF] Schrank | Pollen and spores from the Tendagru Beds, Upper Jurassic and Lower Cretaceous of southeast Tanzania: palynostratigraphical and paleoecological implications[END_REF][START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]Appendix 2).

Moreover, the recurring presence of bryophytic species of Stereisporites and Cingutriletes from JCO B to JCO 15 suggests the possible existence of low-oxygenation related environments, such as in swamps or peat bogs [START_REF] Kujau | Reconstructing Valanginian (Early Cretaceous) mid-latitude vegetation and climate dynamics on spore-pollen assemblages[END_REF]Appendices 1, 2). Thus, the palaeontological and palynological composition corresponding to the second palynological interval suggests progressive establishment of inner lagoonal-type or backswamp environment, becoming increasingly open to very occasional marine inputs, and characterized by a more xeric vegetation dominated by plants producing pollen grains attributed to the Cheirolepidiaceae and Cupressaceae families (including Taxodiaceae), associated with a similar fern and angiosperm community as described for the first palynological interval. This type of environment, periodically flooded by marine or brackish waters, is known to be colonized by mangrove vegetation in tropical and subtropical latitudes [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. [START_REF] Batten | Wealden palaeoecology from the distribution of plant fossils[END_REF] and [START_REF] Gomez | Diversity and histology of a plant litter bed from the Cenomanian of Archingeay-Les Nouillers (southwestern France)[END_REF] already suggested that Cenomanian vegetation from Western Europe and notably Charentes (western France) could be related to mangroves or salt-marsh environments, which could also be the case of the Jaunay-Clan vegetation.

Botanical relationships between macro-and microfossils

Authors of species that are listed in Appendix 1 are not indicated in the text.

Abundant fern fronds have been recovered from the Jaunay-Clan clay deposits, and have been identified as Ruffordia goeppertii (Dunker) Seward, Cladophlebis sp., Sphenopteris sp., and Osmundophyllum sp. [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]; Table 1).

The dispersed spores produced by Ruffordia geoppertii have been previously documented with details [START_REF] Hughes | Descriptions of schizaeaceous spores taken from Early Cretaceous macrofossils[END_REF][START_REF] Deng | Relationship between the Early Cretaceous Ruffordia goepperti and dispersed spores Cicatricosisporites[END_REF]. They belong to the anemiaceous genus Cicatricosisporites, and several species have been described as associated dispersed spores, namely Cicatricosisporites goeppertii (Seward) Groot et Penny, Cicatricosisporites aralica (Bolchovitina) Brenner, and Cicatricosisporites australiensis (Cookson) Potonié.

Because the specific epithet applied to C. goepperti and C. aralica also refers to a form genus of foliage, those species cannot be considered as valid; C. australiensis is thus considered as the effective name of the taxon [START_REF] Ames | Cretaceous Spores and Pollen from the USA and the USSR[END_REF][START_REF] Deng | Relationship between the Early Cretaceous Ruffordia goepperti and dispersed spores Cicatricosisporites[END_REF]. No form identified as C. australiensis has been recovered from the Jaunay-Clan samples, but fairly similar palynomorphs to the holotypes of C. goeppertii and C. aralica have been encountered, and identified as Cicatricosisporites hughesii (Pl. IV.C). Specific differences of anemiaceous Cretaceous dispersed spores are often based on slight morphological variations, and do not take into account a large spectrum of possible intraspecific variability, resulting in numerous overlapping diagnoses. It is then possible that the spores identified as C. hughesii could belong to the same biological species as those identified as C. australiensis.

Reproductive structures of a Cretaceous fern recovered from Canada, and identified as Cladophlebis dunkeri (Schimper) Seward have been observed by [START_REF] Radforth | An analysis of Cladophlebis (Klukia) dunkeri Schimper, a Mesozoic fern from western Canada[END_REF].

They described associated cicatricose trilete spores, which Balme (1995) treated as Cicatricosisporites ludbrookii. Although more typical of older assemblages, this species has been recorded herein in the JCO 13 assemblage (Table 1; Pl. IV.D), and could well have been produced by similar forms as the foliage identified as Cladophlebis sp. However, [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF] specify that this specimen of Cladophlebis sp. belongs to the family Osmundaceae.

The potential corresponding dispersed spores could then belong to the only osmundaceous species recorded, Todisporites major (Pl. II.R), which could be the case for Osmundophyllum sp.

It is quite difficult to discuss the nature of the spores produced by the specimen identified as Sphenopteris sp., because of the wide use of this morphogenus for various foliage types from both Palaeozoic and Mesozoic assemblages. Spores as varied as Deltoidospora, Cicatricosisporites, Apiculatasporites, and Leiotriletes have been identified as dispersed spores of foliage of Sphenopteris [START_REF] Balme | Fossil in situ spores and pollen grains: an annotated catalogue[END_REF]. [START_REF] Greguš | Revision of Cenomanian flora from the Maletín sandstone[END_REF] described pseudodichotomous leaf fronds which they linked to Gleicheniaceae species and called Gleicheniaceaephyllum kurrianum. No spores were recorded in situ, but one can infer that Gleicheniiidites producers may have resembled this form, and based on the great abundance of Gleicheniidites, similar specimens could well be found in the Jaunay-Clan area in due course.

The gymnosperm foliage genera have been identified as Brachyphyllum, Dammarophyllum, and Pagiophyllum. Numerous reproductive parts associated with Brachyphyllum have been found with in situ pollen grains. They were attributed to the araucariaceous genera Araucariacites [START_REF] Balme | Fossil in situ spores and pollen grains: an annotated catalogue[END_REF], which is fairly abundant at Jaunay-Clan, and Callialasporites, which has only been found as a single specimen. Those two genera could actually belong to the same biological species, as noted by [START_REF] Van Konijnenburg-Van Cittert | In situ gymnosperm pollen from the Middle Jurassic of Yorkshire[END_REF], who found both fossil-genera within pollen sacs attributed to a Jurassic species of Brachyphyllum.

The morphogenus Pagiophyllum is often considered to belong to the family Cheirolepidiaceae. Several species of the fertile organ Classostrobus have been found with both leafy shoots of Pagiophyllum and associated pollen grains, always belonging to Classopollis [START_REF] Thévenard | Les coniférales du Jurassique inférieur du gisement de Chaldecoste, bassin des Causses (Lozère, France)[END_REF][START_REF] Balme | Fossil in situ spores and pollen grains: an annotated catalogue[END_REF], which is the dominant form at Jaunay-Clan. It is interesting to note that the common Cenomanian cheirolepidiaceous foliage species Frenelopsis alata (Feistmantel) Knobloch, which has been found in Cenomanian deposits from Maine-et-Loire associated with in situ Classopollis pollen grains [START_REF] Pons | Les organes reproducteurs de Frenelopsis alata (K. Feistm.) Knobloch, Cheirolepidiaceae du Cénomanien de l'Anjou[END_REF], has not been recorded from the Jaunay-Clan deposits. This is probably because this form is associated with fairly rigorous xeric conditions due to the immediate proximity of the coast line [START_REF] Pons | Paléoclimatologie comparée de deux gisements du Crétacé supérieur d'Europe occidentale[END_REF], while the Jaunay-Clan assemblage was probably formed in a more proximal environment. The great abundance of Classopollis could then be explained by the presence of Pagiophyllum. The morphogenus Dammarophyllum sp. has been linked to either the Araucariaceae or Podocarpaceae [START_REF] Kvaček | Foliage of a broad leaved conifer Dammarophyllum from the Cenomanian of Bohemia. Časopis Národního muzea[END_REF], but no fertile organs or pollen grain have been found in connection with the leafy stems so far. [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF] recorded two species of angiosperm foliage. Eucalyptolaurus depreii Coiffard et al. is considered to belong to the Lauraceae family, but no pollen grains have been associated with this species [START_REF] Coiffard | Intramarginal veined Lauraceae leaves from the Albien-Cenomanian of Charente-Maritime (Western France)[END_REF]. Pollen produced by modern Lauraceae can be of four morphological types: A. spheroidal, apolar, spinulose; B. oblate-peroblate, isopolar, slightly to strongly verrucate; C. spheroidal, apolar, strongly verructae/spinuloid; D. spheroidal, para-isopolar, striate (Van der [START_REF] Van Der Merwe | Pollen types in the Lauraceae[END_REF]. No pollen grains meeting those criteria have been recognized in the Jaunay-Clan palynoflora. The resulting lack of pollen evidence for Lauraceae in Late Cretaceous and Cenozoic floras that are rich in lauraceous leaves has been long recognized by paleobotanists, and might be related to the preferential degradation of the associated pollen grains [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF].

Finally, Ploufolia sp. is believed to be an aquatic angiosperm belonging to the Nymphaeales, which genus has been first described in upper Albian deposits of Spain [START_REF] Sender | Ploufolia cerciforme gen. et comb. nov.: aquatic angiosperm leaves from the Upper Albian of north-eastern Spain[END_REF].

No pollen grain has been associated with this species, and fossil pollen grains of Nymphaeales are very scarce. Modern Nympheaceae are associated with zonasulculate pollen grains characterized by their echinate, baculate, or gemmate ornamentation [START_REF] Jones | The Northwest European Pollen Flora, 25: Nymphaeaceae[END_REF], but no pollen grains meeting those criteria have been recognized in the Jaunay-Clan palynoflora. It has to be noted that the association of Ploufolia with Nympheales is uncertain, since it is much smaller than leaves of modern Nymphaeaceae and lacks fine venation that might support this (Doyle, comm. pers.). Ploufolia could well belong to another basal angiosperm group which has yet to be determined, and associated pollen grains could in fact be present in the Jaunay-Clan association.

Comparisons with Cenomanian assemblages from France and neighboring areas

The taxonomic composition of the JCO palynoflora has been compared to 12 other Cenomanian palynological assemblages recovered from lowest Cenomanian (lithological subunits A1-A2), mid-lower Cenomanian (lithological subunits B1-B2), and middle Cenomanian strata of western France (Table 2; Appendix 3; see Fig. 1 for location of the studied sites and references). The JCO assemblage is most similar to the assemblages recovered from the mid-lower Cenomanian lithological subunits B1-B2 from Charente-Maritime and Charente, displaying the highest similarity index (Table 2). While less diversified than the oldest and youngest assemblages, the four palynofloras considered herein share between 45% and 62% of common species with the JCO assemblage. However, the associated macroremains recovered from Fouras and Aix Island are far less diversified than the Jaunay-Clan paleoflora, gathering only a few specimens identified as Frenelopsis alata, Glenrosa sp., Brachyphyllum sp., and several wood fragments [START_REF] Gomez | Assemblages floristiques de l'Albien-Cénomanien de Charente-Maritime (SO France)[END_REF][START_REF] Néraudeau | Amber, plant and vertebrate fossils from the Lower Cenomanian paralic facies of Aix Island (Charente-Maritime, SW France)[END_REF]Table 1). No angiosperm remains were identified.

The JCO assemblage is also very similar to the Archingeay Les-Nouillers and Cadeuil assemblages, which were recovered from the lower Cenomanian A2 subunit of Charente-Maritime [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. They share between 40 and 50 common species, which are well balanced between the miospores, gymnosperm pollen grains, and angiosperm pollen grains (Appendix 3; Table 2). Their high similarity index could however be related to the great diversity of palynomorphs identified at these two sites, which have been abundantly sampled in comparison to the other Cenomanian outcrops from Charente-Maritime and Charente [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. The Archingeay-Les Nouillers palynoflora is associated with a fairly rich macroflora, including various siliceous gymnosperm remains and leaves of Eucalyptolaurus depreii [START_REF] Néraudeau | Un nouveau gisement à ambre insectifère et à végétaux (Albien terminal probable): Archingeay (Charente-Maritime, France)[END_REF][START_REF] Dejax | Analyse palynologique de l'argile lignitifère à ambre de l'Albien terminal d'Archingeay (Charente-Maritime, France)[END_REF][START_REF] Gomez | Diversity and histology of a plant litter bed from the Cenomanian of Archingeay-Les Nouillers (southwestern France)[END_REF][START_REF] Coiffard | Intramarginal veined Lauraceae leaves from the Albien-Cenomanian of Charente-Maritime (Western France)[END_REF][START_REF] Moreau | Inclusions of conifers, echinoids, foraminifers and sponges in flints from the Cenomanian of Charente-Maritime (France): Contribution of synchrotron microtomography[END_REF][START_REF] Moreau | Albian flora from Archingeay-Les Nouillers (Charente-Maritime): comparison and synthesis of Cretaceous mesoand macro-remains from the Aquitaine Basin (southwestern France)[END_REF]; Table 1). Most of the macroflora is preserved in flints, but a few specimens of fossil wood and angiosperm leaves have been found as impressions/compressions. They are less diverse and well-preserved than the Jaunay-Clan paleoflora, mostly including portions of Frenelopsis cuticles and wood remains [START_REF] Moreau | Albian flora from Archingeay-Les Nouillers (Charente-Maritime): comparison and synthesis of Cretaceous mesoand macro-remains from the Aquitaine Basin (southwestern France)[END_REF]. Another exceptional lower Cenomanian angiosperm leaf-bearing site has been discovered in the strata ascribed to the lithological subunit A2, at Puy-Puy (Charente-Maritime; Fig. 1; Le Diouron, 2005, unpublished; Table 1). However, while the underlying layers have yielded numerous spores and pollen grains, the plant-bearing clay levels were proven to be barren of any palynomorphs [START_REF] Peyrot | Apport de données palynologiques à la reconstruction paléoenvironnementale de l'Albo-Cénomanien des Charentes (Sud-Ouest de la France)[END_REF]pers. obs.).

The JCO palynological assemblage shares the least similarities with the middle Cenomanian palynofloras from Vendée, Mayenne, and Maine-et-Loire, presenting a similarity index of only 0.14 (Fig. 1; Table 2). However, they share the highest number of exclusive common species, mostly represented by species of Camarozonosporites recovered from both Jaunay-Clan and La Garnache (Appendix 3). Also, specimens attributed to Molaspora lobata and similar forms were only recovered from Ecouflant quarries and Jaunay-Clan (Pl. VIII.D), while absent from lower Cenomanian mesofossil assemblages of Charente-Maritime (Fig. 1; [START_REF] Batten | Megaspores from mid Cretaceous deposits in western France and their biostratigraphic and palaeoenvironmental significance[END_REF]. On other aspects, these assemblages are quite different from the JCO assemblage, mainly because of the increasing diversity of angiosperm pollen grains, especially Normapolles [START_REF] Juignet | Les argiles noires d'Écommoy (Sarthe): Précisions sédimentologiques et palynologiques[END_REF][START_REF] Azéma | Étude palynologique préliminaire du gisement cénomanien de la Bironnière, Vendée (France)[END_REF][START_REF] Azéma | Des miospores du Cénomanien moyen[END_REF][START_REF] Néraudeau | Upper Cretaceous amber from Vendée, north-western France: Age dating and geological, chemical, and palaeontological characteristics[END_REF]Appendix 3). The composition of the Hucheloup palynoflora differs greatly from the JCO assemblage (Table 2), but a similar paleoflora has been recovered from the associated strata. It is composed of several taxa of plant preserved in impressions/compressions, ascribed to filicophytes, gymnosperms and angiosperms [START_REF] Fleury | Palaeobotanical investigation of a Cenomanian clay lens in Hucheloup Quarry, Maine-et-Loire, NW France : Taxonomic, stratigraphic and palaeoenvironmental implications[END_REF]; Table 1). While differing by the dominance of Frenelospsis alata, which is absent from JCO, and the poorer state of preservation of the macroremains, the Hucheloup paleoflora is the most similar plant assemblage to JCO recovered from France so far.

Elsewhere in Europe, numerous mid-Cretaceous outcrops have yielded abundant and diversified angiosperm-rich plant assemblages (see [START_REF] Coiffard | Early angiosperm ecology: evidence from the Albian-Cenomanian of Europe[END_REF] for overview), but only a few studies have acknowledged their associated palynoflora. The Peruc-Korycany Formation (Bohemian massifs, Czech Republic) yielded numerous plant remains [START_REF] Kvaček | Comparison of Cenomanian floras from western interior North America and Central Europe[END_REF], some of which have already been compared to the JCO paleoflora [START_REF] Valentin | Plant-dominated assemblage and invertebrates from the Lower Cenomanian of Jaunay-Clan, western France[END_REF]. Numerous associated angiosperm pollen grains have also been described, including several forms recovered from the JCO assemblage, such as Tricolpites nemejcii and T. vulgaris (Pactlová, 1971(Pactlová, , 1977(Pactlová, , 1978)). However, the overall palynological assemblage differs by the high abundance of Normapolles prollen grains, the Peruc-Korycany Formation being considered as middle Cenomanian (Pactlová, 1978).

No Cenomanian macro-and microflora has been described from Spain and Portugal, but both the palaeobotanical and palynological assemblages from Jaunay-Clan present numerous similarities with the uppermost Albian Spanish flora recovered from Teruel Province. They both yielded very well-preserved angiosperm macro and micro-remains, including Ploufolia [START_REF] Sender | A new uppermost Albian flora from Teruel province, northeastern Spain[END_REF]. The Teruel Province palynoflora is however less diversified, and lacks typical Cenomanian stratigraphic markers, such as Tricolpites nemejcii and Retitricolporites decorosus [START_REF] Sender | A new uppermost Albian flora from Teruel province, northeastern Spain[END_REF]. The same comment applies for the latest Albian palynoflora from the Maestrazgo Basin (Spain), which is in every other way very similar to the JCO palynoflora [START_REF] Villanueva-Amadoz | Palynological studies of the boundary marls unit (Albian-Cenomanian) from northeastern Spain. Paleophytogeographical implications[END_REF]. The presence of leaves macroremains was noted by Villanueva-Amadoz et al. ( 2011), but their taxonomical content has yet to be described. Numerous other studies on well-preserved Spanish Cretaceous plant macroremains have been published, but most of them deal with Early Cretaceous assemblages (Alvarez-Ramis et al., 1981;[START_REF] Gomez | Découverte d'une flore à Ginkgoales, Bennettitales et Coniférales dans le Crétacé inférieur de la formation Escucha (Chaine Ibérique Orientale, Teruel, Espagne)[END_REF][START_REF] Gomez | A new species of Nehvidzya (Ginkgoales) from the Lower Cretaceous of the Iberian Ranges (Spain)[END_REF][START_REF] Gomez | Plant taphonomy and palaeoecology in the lacustrine Uña Delta (Late Barremian, Iberian Ranges, Spain)[END_REF]Gomez et al., , 2002a)). Their associated palynological content has sometimes been independently described [START_REF] Peyrot | Contributions to the palaeoenvironmental knowledge of the Escucha Formation in the Lower Cretaceous Oliete Sub-basin, Teruel, Spain[END_REF][START_REF] Barrón | Palynology of Aptian and upper Albian (Lower Cretaceous) amber-bearing outcrops of the southern margin of the Basque-Cantabrian basin (northern Spain)[END_REF].

Finally, several middle to upper Cenomanian palaeofloras have been described from Veneto and Campania regions (Italy; Gomez et al., 2002b;[START_REF] Bartiromo | A new terrestrial plant-rich Fossil-Lagerstätte from the middle Cenomanian (Late Cretaceous) of the Apennine Carbonate Platform (Magliano Vetere, southern Italy): Depositional and palaeoenvironmental settings[END_REF], but these are mostly composed of Frenelopsis remains, and no associate palynoflora was presented. The association of the Jaunay-Clan continental palynoflora and palaeoflora is thus considered to be the most diversified Cenomanian combined palaeobotanical and palynological assemblage described from Western Europe so far.

Conclusion

The Jaunay-Clan botanical assemblage is exceptional as it gathers both a rich and diverse macro-and palynoflora, allowing us to sketch a more complete picture of the French Cenomanian vegetation than previously known. The seven productive palynological assemblages show slight environmental changes, grading from a calm freshwater environment to an environment more open to occasional marine inputs, in a backswamp or an inner lagoon.

These changes mark the beginning of the Cenomanian-Turonian transgression, progressively flooding emerged areas in a southwestern-northeastern direction (Moreau, 1993a(Moreau, -b, 1996)). This hypothesis corroborates a slightly younger age for the Jaunay-Clan assemblage than the age of the assemblages recovered from the lower Cenomanian of Charente-Maritime and Charente, except for the localities of Fouras and La Buzinie [START_REF] Peyrot | Early Cenomanian palynofloras and inferred resiniferous forests and vegetation types in Charentes (southwestern France)[END_REF]. Other mid-Cretaceous assemblages from Europe yielded either rich macroflora or relatively rich palynoflora, but at the exception of Bohemian assemblages, both types of fossils are rarely as well-preserved and/or diversified, making the association of the Jaunay-Clan continental palynoflora and palaeoflora the most diversified Cenomanian assemblage with both palaeobotanical & palynological data described so far in Western Europe. and numbered hereafter. 1 Azéma, 1979; 2 Azéma et al., 1972; 3 Azéma et al., 1981; 4 Azéma et al., 1990; 5 Batten et al., 2010; 6 Berthelin and Pons, 1999; 7 Boura et al., 2019; 8 Boureau and Veillet-Bartoszewska, 1955; 9 Coiffard et al., 2009; 10 Crié, 1890; 11 Deák and Combaz, 1967; 12 Fleury et al., 2017; 13 Gomez et al., 2004; 14 Juignet and Médus, 1971; 15 Le Diouron, 2005 (unpublished); 16 Méon et al., 2004; 17 Moreau, 1993a-b; 18 Moreau et al., 2014; 19 Moreau et al., 2017; 20 Néraudeau et al., 2002; 21 Néraudeau et al., 2005; 22 Néraudeau et al., 2009; 23 Néraudeau et al., 2013; 24 Néraudeau et al., 2017; 25 Perrichot, 2003; 26 Peyrot et al., 2005; 27 Peyrot et al., 2019; 28 Pons, 1979; 29 Pons et al., 1980; 30 Robin et al., 2018; 31 Valentin et al., 2014; 32 Azéma and Ters, 1971; 33 Durand and Ters, 1958; 34 Lecointre and Carpentier, 1939; 35 Alvárez-Ramis et al., 1981; 36 Néraudeau et al., 2003. Figure 2. Geological map of the Jaunay-Clan area based on the BRGM geological map 1/50000 n°567 -Vouneuil-sur-Vienne [START_REF] Bourgueil | Notice de la carte géologique de la France à 1/50 000[END_REF], with location of the outcrop (red star).

  II.T; Pl. III.A-III.C) and Clavifera (Pl. II.S), and by spores of the Cyatheales (20%), ascribed to the genera Cibotiumspora (Pl. IV.K), Cyathidites (Pl. IV.L), and Deltoidospora (Appendices 1, 2). The spores associated with the Anemiaceae represent 5% of the whole assemblages, but are the most diversified group, with ten and five species of Appendicisporites (Pl.III.K-III.S), Cicatricosisporites (Pl. IV.A-IV.F), Costatoperforosporites (Pl. IV.G), and Distaltriangulisporites (Pl. IV.H), including three species only recorded in those two assemblages: Appendicisporites fucosus, A. cf. A. potomacensis, and Distaltriangulisporites perplexus (Appendix 1). Lycophytes also represent ca. 5% of the assemblages, mostly represented by species belonging to Camarozonosporites (Pls. I.O-II.G). The other spore groups are less abundant, less diversified, and are represented by species belonging to Microreticulatisporites (Filicophyte indet.; Pl. IV.S, IV.T), Laevigatosporites (Polypodiales; Pl. IV.M) and Triporoletes (Bryophyta; Pl. I.L-I.N). The gymnosperm spectrum is dominated by bisaccate pollen grains ascribed to the Pinaceae/Podocarpaceae (Pls. V.J-VI.A), and identified as Pristinuspollenites, Parvisaccites, and Rugubivesiculites. Gymnosperm pollen grains are taxonomically well balanced between species of Araucariacites (Pl. VI.B), Balmeiopsis (Araucariaceae; Pl. VI.C), Classopollis (Cheirolepidiaceae; Pl. VI.G), Inaperturopollenites (Cupressaceae-including Taxodiaceae; Pl. VI.H), Equisetosporites (Pl. VI.L), Eucommiidites (Gnetophyta; Pl. VI.M, VI.N), Afropollis (Pl. VI.K), and Vitreisporites (Caytoniales). Eight species of angiosperm pollen grains were recovered from the first interval, especially from JCO D, two species having only been recovered from JCO 8 (Fig. 5D2; Appendix 1). They are composed of one species of Clavatipollenites (Chloranthaceae; Pl. VII.A), one species of Pennipollis and Transitoripollis (?Chloranthaceae/?Ceratophyllaceae; Pls. VI.O, VI.P, VII.B, VII.C), two species of Monosulcites (probable monocots or more basal angiosperms; Pl. VI.Q), one species of Nyssapollenites and Retitrescolpites (eudicots, Pl. VII.D, VII.F, VII.G), and one species of Dichastopollenites (uncertain botanical affinities; Pl.

(

  Bryophyta; Pl. I.I-I.K), Densoisporites, Foveosporites, Leptolepidites, Lycopodiacidites, Wilsonisporites (Lycophyta; Pls. II.I, IV.O, IV.P, II.K, II.L, II.Q), all representatives of Osmundaceae (Pl. II.R), Matonisporites (Matoniaceae; Pl. III.G), Ischyosporites (Lygodiaceae; Pl. III.H), Crybelosporites (Marsileaceae; Pl. IV.J), Lophotriletes, Foveotriletes, Patellasporites, Scopusporis, and Undulatisporites (Filicophytes indet.; Pls. II.J, V.C-V.F, III.J, V.G; Appendix 1).

  Phimopollenites (Pl. VII.E), Striatopollis (Pl. VII.J, VII.I), Retitrescolpites (Pl. VII.F), Retitricolporites (Pl. VII.H), Tricolpites (Pl. VII.L-VII.O), and Rousea (Pl. 7G) were only encountered in these two assemblages (Appendix 1). Parallel to the abrupt increase in the abundance of Classopollis, this interval is also characterized by the appearance of dinocysts (Pl. I.A-I.H), absent in the first interval. Their relative abundance is very low, representing between 1% and 2% of the whole assemblages. They are mostly represented by Surculosphaeridium longifurcatum (Pl. I.E), but nine species were recorded altogether, with a peak of diversity in the JCO 13 assemblage which yielded five species (Appendix 1). Occasional freshwater algae have also been observed, mostly belonging to Schizosporis (Pl. VII.S, VII.T). They are more diversified in the JCO B-JCO A assemblages than in the youngest assemblages. A small assemblage of megaspores was recovered from preparation MFP513, including Minerisporites sp. (Pl. VIII.A), Minerisporites cf. sp. 1 sensu Batten in Batten et al. (2010) (Pl. VIII.B), Paxillitriletes sp. (Pl. VIII.C), and Molaspora cf. lobata (Pl. VIII.D). A specimen attributed to Arcellites reticulatus (Pl. IV.I) has been found amongst the miospore preparations.

Figure captions Figure 1 .

 captions1 Figure captions

Figure 3 .

 3 Figure 3. Stratigraphic section of Jaunay-Clan-Ormeau-Saint-Denis outcrop, with location of recovered samples and main features.

Figure 4 .

 4 Figure 4. Rarefaction curves of the palynological assemblages recovered from the Jaunay-Clan-Ormeau-Saint-Denis productive samples. Numerical data are provided in Appendix 3.

Figure 5 .

 5 Figure 5. Plots of the abundance and diversity of the Jaunay-Clan-Ormeau-Saint-Denis palynological assemblages, based on the botanical affinities of the various spore and pollen morphotypes (Appendix 2). A. Abundance and diversity of the main groups of palynomorphs. B. Abundance and diversity of bryophytic and fern spores. C. Abundance and diversity of gymnosperm pollen grains. D. Number of specimens and diversity of angiosperm pollen grains, which were not abundant enough to be displayed in a comparative relative abundance plot. Abundance plots are based on N=250 (except for JCO 8, N=163). Diversity plots are based on N=163-4100. Species list and numerical data are provided in Appendices 1, 3.

Acknowledgements

The field work was conducted under an agreement for paleontological researches signed between Lisea and Cosea (VINCI group) and the PALAIOS society. Financial support was provided in part by the Lisea foundation, the Vienne department, the municipality communities of the Pays Chauvinois and the Valdivienne municipality. We are grateful to J.A. Doyle and the second anonymous referee for their thorough reviews, and helpful comments on the manuscript.

Table 1. Systematic list of foliage remains recovered from Cenomanian outcrops in western France, along with number of pollen and spores species identified in the associated strata. For location of outcrops and references, see Figure 1.