# Impact of the EECO on mammalian faunas: New Ypresian localities from Montpellier (France), a multidisciplinary approach

Fabrice Lihoreau<sup>a,*</sup>, Johan Yans<sup>b</sup>, Mouloud Benammi<sup>c</sup>, Flavia Girard<sup>d</sup>, Gregory Ballas<sup>d</sup>, Hélène Bourget<sup>a</sup>, Cindy Boyrie<sup>a,d</sup>, Jacinthe Caillaud<sup>e</sup>, Anne-Lise Charruault<sup>a</sup>, Killian Gernelle<sup>a</sup>, Floréal Solé<sup>f</sup>, Xavier Valentin<sup>c</sup>, Quentin Vautrin<sup>a,g</sup>, Monique Vianey-Liaud<sup>a</sup>, Rodolphe Tabuce<sup>a</sup>

## ARTICLE INFO

**Article history:**

Received 19 July 2024

Received in revised form 20 December 2024

Accepted 16 January 2025

Available online xxxx

**Keywords:**

Systematics

Biostratigraphy

Magnetostatigraphy

Chemostratigraphy

Eocene

Hyperthermal events

## ABSTRACT

An integrative chronological study on a new terrestrial sedimentary sequence north of Montpellier (southern France) yields an age ranging from 52.1 to 49.7 Ma. This sequence contains three new mammalian fossil localities, for the first time described in this study, and is associated with the nearby specifically rich site of Mas de Gimel (MP10 – European Mammalian Paleogene Reference Scale [MP]). This study constrains the age of the Grauvian ELMA [European Land Mammal Age] with respect to the geological time scale, suggesting that it is more contemporary with the EECO (Early Eocene Climatic Optimum) than previously considered, and in particular with the period of High Amplitude Climate Fluctuations. These new faunas and data allow us to discuss the relevance of the European Mammalian Paleogene Reference Scale [MP] and to propose new continental biozones for the late Ypresian. It also demonstrates that the late Neustrian fauna (MP8 + 9) is contemporary with the onset of the EECO and that there may be several late- and post-EECO faunas in southern France. Our study moreover suggests phases of diversification during the warm periods, and extinction during the cooling, as observed in North America. Future refined dating of the European fossil localities of this key period will help to discuss the impact of global warming on mammalian communities in the frame of further intercontinental comparisons.

© 2025 The Geologists' Association. Published by Elsevier Ltd. This is an open access article under the CC BY license

(http://creativecommons.org/licenses/by/4.0/).

## 1. Introduction

The Early Eocene epoch has been the setting for significant climatic fluctuations, including the warmest periods of the Cenozoic era (Zachos et al., 2008; Westerhold et al., 2020). Indeed, a series of thirty brief hyperthermal events have been documented (e.g., the Paleocene-Eocene Thermal Maximum, PETM; Kennett and Stott, 1991; McInerney and Wing, 2011), over which a long-term event, the Early Eocene Climatic Optimum (EECO; Westerhold et al., 2018), is superimposed. This long-term event is thought to have strongly influenced land mammal diversity (Woodburne et al., 2009a), with a high level of first and last appearances (Woodburne et al., 2009b). Indeed, this extreme global warming evidenced by the evolution of the benthic foraminiferal negative δ¹⁸O record between ~53 and 49 Ma (from the

negative isotopic excursion of δ¹⁸O C24n2rH1/J to the end of the magnetic chron C22n; Westerhold et al., 2018) is considered as the warmest Cenozoic period (Westerhold et al., 2020). It could correspond to a + 10 to + 16 °C increase in global marine superficial temperature (close to 27 °C) compared to pre-industrial times (Inglis et al., 2020). Up to now, this effect on land mammal diversity has only been documented from the Western Interior of North America (Woodburne et al., 2009a), thus calling into question the global nature of the effects of this Eocene warming. To this end, one of the major scientific hurdles to be overcome is to obtain refined ages for the European fossiliferous localities of the Late Ypresian. The use of the Mammalian Paleogene (MP) reference-levels for dating continental strata (Schmidt-Kittler et al., 1987; Biochrom'97, 1997) does not permit refined correlation with the Geological Time Scale (GTS; Hooker, 1996a; Speijer et al., 2020). With only three reference levels during the whole Ypresian (i.e., MP7, MP8 + 9, and MP10), it is not possible to describe a biological event in the European continental Ypresian with the resolution of the main climatic changes recorded in the ocean.

<footnote><sup>a</sup> Institut de Sciences de l'Evolution, Univ Montpellier, CNRS, IRD, Montpellier, France</footnote>

<footnote><sup>b</sup> Département de Géologie, Institut of Life, Earth and Environment, ILEE, Namur, Belgium</footnote>

<footnote><sup>c</sup> Laboratoire Paléontologie Evolution Paléoécosystèmes Paléoprimatologie, Poitiers, France</footnote>

<footnote><sup>d</sup> Géosciences Montpellier, Université de Montpellier, CNRS, Montpellier, France</footnote>

<footnote><sup>e</sup> Laboratoire d'Océanologie et de Géosciences, Université du Littoral Côte d'Opale, Université de Lille, CNRS, IRD, Wimereux, France</footnote>

<footnote><sup>f</sup> Royal Belgian Institute of Natural Sciences, Brussels, Belgium</footnote>

<footnote><sup>g</sup> Réserve Naturelle Nationale d'Intérêt Géologique du Lot, Parc Naturel Régional des Causses du Quercy, Geoparc Mondial UNESCO des Causses du Quercy, Cœur-de-Causse, France</footnote>

<footnote>* Corresponding author at: Institut des Sciences de l'Evolution de Montpellier, CC65 place eugène Bataillon, 34095 Montpellier cedex 5, France.
E-mail address: fabrice.lihoreau@umontpellier.fr (F. Lihoreau).</footnote>
The end of the Ypresian for European continental strata is related to MP10, for which the reference level is Grauves in the Paris Basin (Schmidt-Kittler et al., 1987). Most of the European MP10-related localities, all also located in the Paris Basin (Saint-Agnan, Chavot, Cuis, Mancy, Monthelon, Venteuil; Biochrom'97, 1997) are not included in a long/continuous stratigraphical sequence and it is therefore difficult, if not impossible, to carry out pertinent geochronological investigations. The only European site related to MP10 and precisely correlated to GTS is Prémontré, in northern France. Indeed, using biostratigraphical correlation with the Merelbeke Clay Member (Belgium), it was proposed that the Prémontré fossiliferous level corresponds to the base of the NP13 (calcareous nannofossil assemblages), just postdating the onset of chron C22r, around 50.4 to 50.3 Ma (Steurbaut et al., 2016). Likewise, the Bracklesham Group (southern England), correlated with the GTS by mean of palaeomagnetism and nannoplankton assemblages, yielded depleted faunas of MP10 affinities (e.g., localities of Dummer's Copse 5iii and Bracklesham Bay W14 and W15) around the NP12-NP13 transition in C22r (Hooker, 1996b). These dates further establish that the fauna reported for MP10 was present during the EECO, at

least immediately after the period of High-Amplitude Climate Fluctuations defined by Westerhold et al. (2018) in C23n and beginning of C22r between 51.5 and 50.9 Ma. However, the questions of how long the faunas referred to near MP10 have persisted and whether they have been influenced by the EECO remain unanswered.

Localities referred to MP10 are also known in southern Europe notably in southern France in the Minervois Basin near Carcassone with the depleted fauna of Azillanet (Marandat, 1986), in Spain with the approximately dated locality of Los Saleres (Crusafont-Pairó, 1967; Femenias-Gual et al., 2016) and some others, such as those in the Graus-Tremp Basin (Badiola et al., 2009). This period is also well documented in the Montpellier area (southern France) with the historic localities of Mas de Piquet (Roman and Genneveaux, 1907) and Coulondres (Hartenberger et al., 1969), and with the taxon-rich localities of Mas de Gimel (38 species) and Naples (Cappetta et al., 1968; Vianey-Liaud et al., 2024). Interestingly, comparisons between the MP10 faunas from southern and northern France suggest the existence of a unique bioprovince, whereas a north-south provincialism has been proposed for the MP7 and MP8 + 9 faunas (Marandat, 1997; Marandat et al.,

<figure><img src="image_1.png" /><figcaption>**Fig. 1.** Geographical location of the studied sections Serres de Vias A–D, north of Montpellier. A, Geological context of the Eocene outcrops (modified from the Montpellier and Saint-Martin-de-Londres 1/50,000 geological maps) and B, geological mapping of the four studied sedimentary sections (SDV-A to D), using aerial view.</figcaption></figure>
2012; Solé et al., 2014). The Montpellier area is critical as it presents a particularly well-exposed Eocene stratigraphical sequence with fossiliferous localities in a fine stratigraphical context that is very different from those known for this period in the Paris Basin, which are only exposed in very short sequences or lack stratigraphical context (e.g., Lecomte, 1994; Neal, 1996; Duprat, 1997). In the vicinity of Coulondres, road developments in north of Montpellier have recently cut through the Eocene relief and provided us with three new fossiliferous localities positioned in a long and continuous stratigraphical terrestrial sequence (Fig. 1). We describe the three new faunas and revise the Coulondres fauna (Hartenberger et al., 1969). The stratigraphical context of these localities, along with accurate outcrop conditions, allows us to manage a chronological approach using methods in addition to biochronology, such as chemostratigraphy coupled with magnetostratigraphy. These methods are powerful tools when used together (e.g., Benammi et al., 2019; Vaucher et al., 2023) and are relevant for the Ypresian, as this period records in marine sediments 7–8 magnetic reversals, 30 isotopic excursions of the δ¹³C and a mid-term positive trend of the δ¹³C shift (Westerhold et al., 2018), allowing refined correlation of the studied continental sections with the GTS (Speijer et al., 2020). The chemostratigraphy used here to date continental sections could also help to correlate with climatic events such as hyperthermals (ETMs) and climatic optima (e.g., EECO; Westerhold et al., 2020). Our refined dating contributes to further discussion of the European biochronology and to assess the impact of climatic fluctuations on the mammalian faunas in Europe for the late Ypresian.

## 2. Geological and depositional setting

The study area is located in the south of France, about 12 km north of the city of Montpellier, on the border between the towns of Les Matelles and Saint Gely-du-Fesc (Fig. 1A). The studied sedimentological sections are outcrops along the D68 (le L.I.E.N.: *Liaison Intercantonale d'Evitement du Nord*) and D986 roadsides, which give access to sedimentary formations described as Lower to Middle Eocene on the local geological map (Andrieux et al., 1971; Fig. 1B). These sediments were deposited in a foreland basin environment, locally related to the north-verging Montpellier Thrust (Hemelsdaël et al., 2021; Ballas et al., 2022; Fig. 1A). Both the basin and the thrust were formed during the Pyrenean NS contraction from Late Cretaceous to late Eocene (Arthaud and Séguret, 1981; Séranne et al., 2021). These sediments were deposited during a quiescent tectonic phase (Debrand-Passard, 1984), in a continental setting forming both siliciclastic and carbonate sedimentary successions (Hartenberger et al., 1969; Freytet et al., 1982; Fig. 1B). This basin has been affected by NW-SE rifting during the Oligocene, creating half-graben basins by the reactivation of inherited NE-SW strike-slip faults (Maerten and Séranne, 1995; Benedicto et al., 1999).

The sedimentary deposits of the studied succession have long been considered to be of Lower to Middle Eocene age (Hartenberger et al., 1969; Andrieux et al., 1971). The sedimentary succession unconditionally overlies both the continental Upper Cretaceous-Paleocene (early Maastrichtian in Vianey-Liaud and Crochet, 1993) and the marine Lower Cretaceous (Berriaso-Valanginian in Bonnet et al., 1971). In the study area, this Upper Cretaceous-Paleocene/Eocene unconformity does not outcrop, but the geological mapping allows us to locate it at about 30 m below the base of the sedimentological log section Serre-de-Vias-A (SDV-A; Fig. 2B). From base to top, the sedimentary succession is historically divided into three fairly continuous lithological units in the Eocene basin of Montpellier: i) a lower sility-dominated unit relative to floodplain deposits, ii) a middle lignite-rich unit relative to peat deposits overlain by, iii) a thick upper limestone-dominated unit traditionally referred to as lacustrine to palustrine limestones called 'calcaires lutétiens' (Hartenberger et al., 1969; Bonnet et al., 1971).

The studied area is known for having yielded important late Ypresian fossiliferous localities, recognisable by their proximity to the brown lignite-rich beds, notably Mas de Piquet (Grabels; Roman and

Genneveaux, 1907), Mas de Gimel (Montpellier; Cappetta et al., 1968; Vianey-Liaud et al., 2024), and Coulondres (Saint-Gely-du-Fesc; Hartenberger et al., 1969). In the vicinity of the latter site, some Eocene plant fossils were discovered and described by Saporta (1868), but their exact localisation remains unknown. Some turtle fragments were also found in this area and deposited in the UM collection since 1862. More recently, the localities of Naples and Naples 2 (Montpellier) appeared to be lateral equivalents of Mas de Gimel (Vianey-Liaud et al., 2024). Road works carried out in this area between Les Matelles and Saint-Gely-du-Fesc since 1997 allowed us to access clear outcrops within the lignite-rich beds, potentially equivalent to the historical fossiliferous localities. In addition to Coulondres, three new fossiliferous localities, namely Plagnol (PLG), Plantade (PLD), and Le Lien (LLN) have been discovered in the eastern slope of the Serre-de-Vias, allowing direct stratigraphical correlations (Figs. 1–2). On the western flank of this relief, the Canlong locality has already yielded some Bartonian fossils (MP14; Crochet et al., 1997). Plagnol (PLG) and Le Lien (LLN), located in the lower sility unit and the middle lignite-rich bed, respectively, separated by only 270 m of distance both on the SDV-A section (Fig. 1B), are within the municipal boundaries of Les Matelles. Plantade (PLD), 820 m south of LLN, on the SDV-D section, is within the municipal boundaries of Saint-Gely-du-Fesc (Fig. 1B), close to the fossiliferous locality of Coulondres (CLR).

## 3. Materials and methods

### 3.1. Stratigraphy

The area was investigated by analysing outcrops, mapping beds on satellite imagery (Fig. 1B) and by measuring sedimentological sections (Fig. 2). Four sedimentological sections, namely Serre-de-Vias (SDV) sections A, B, C, and D (Fig. 2), were logged with a spacing between them of about 0.5 to 1 km depending on outcrop conditions. The sedimentological sections were logged at the scale of individual beds (1:100 scale), noting grain size, bed thickness, bed contacts and geometry, and internal sedimentary structures. Correlations between the four cross sections were realised both by physical bed to bed correlation in the field and by bed mapping from aerial and satellite images (Google Earth Pro software and https://remonterletemps.ign.fr).

### 3.2. Palaeontology

Besides the description of the newly discovered fossils from Plagnol (PLG), Plantade (PLD), and Le Lien (LLN), we took the opportunity of this study to revise the fauna of Coulondres (CLR). This locality was first described by Hartenberger et al. (1969, 1970), who noted four mammal species, namely *Peratherium* indet., *Palaeochiropteryx* sp., *Microparamys* sp., and *Artiodactyla* indet. Since then, only the study of the metatherians has been published (Crochet, 1980). The locality of Coulondres is a lignite horizon. It has been confused several times with the Saint-Gely-du-Fesc lignite, which is another locality that yielded two mammal species described by Gervais (1848). The Saint-Gely-du-Fesc lignite is more recent (late Eocene, MP18), but geographically close to Coulondres (see Hartenberger et al., 1969).

In Coulondres and the three new localities (PLG, PLD, LLN), very few mammal fossils have been found by prospecting on the outcrop: the three fossils from Plantade and some large mammals, chelonians and crocodilians from Le Lien. Otherwise, most of the fossils were extracted from the matrix using chemicals. For the locality of Le Lien, which consists of a brownish marl rich in organic matter, washing with oxygenated water allowed us to sieve (from 2 mm to 0.7 mm) and collect the fossil material. The lithology of Plagnol is different, with tough limestones, for which a treatment with formic acid was necessary before washing and sifting (from 2 mm to 0.7 mm). At least 240 kg of Plagnol limestone, collected in 2018 and 2020, and at least 500 kg of marl from Le Lien, collected during several successive field missions from 2008 to
<figure><img src="image_2.png" /><figcaption>**Fig. 2.** A–H. Geochronological data from the Le Lien area. A, Outcrop photography of section SDV-A with locations of the Plagnol and Le Lien fossiliferous beds; B, synthetic sedimentological log of the three SDV-A–C sections; C, $\delta^{13}C_{org}$ values (‰ VPDB) of the SDV-A–C sections; D, palaeomagnetic data (VGP) of the SDV-A–C sections; E, sedimentological log of SDV-D section; F, $\delta^{13}C_{org}$ values (‰ VPDB) of the SDV-D section; G, palaeomagnetic data (VGP) of the SDV-D section; H, outcrop photography of SDV-D section with location of the Plantade fossil level; the positive and negative virtual geomagnetic pole (VGP) latitudes represent normal (N) and reverse (R) polarities, respectively.</figcaption></figure>

2020, were processed to recover the studied fauna. The Coulondres material was obtained in 1968 by washing lignite sediments from the mine deposit.

The material was then studied for taxonomic analysis by anatomical comparison, based mainly on the collections of the University of Montpellier and of the Muséum National d'Histoire Naturelle de Paris
(original specimens and casts). The new material (Tables 1–3) is housed
in the collection of the University of Montpellier.

Small mammals are illustrated by X-ray µCT surface reconstructions using the EasyTom 150 microtomograph (MRI platform at the ISEM laboratory, University of Montpellier). Large mammal teeth are pictured with a Nikon D750/micro-Nikkor 105 mm using Combine ZP for focus stacking. Measurements (in mm) have been made by Leica Application Suite (LAS) for small specimens and calliper for larger specimens. Measurements follow main methodology applied for each mammal group (see Vianey-Liaud et al., 2024).

3.3. Palaeomagnetism

Rock samples for palaeomagnetic analysis were collected from the four sedimentological sections SDV-A, B, C, and D (Figs. 1–2), with an average spacing of 1 to 10 m. Palaeomagnetic sampling was done using either a hand rasp or a diamond bit water-cooled gasoline-powered drill. Red and orange argillaceous siltstones (generally), very fine sandstones, limestones, and marls are among the lithologies sampled. The samples were oriented *in situ* with a magnetic compass as well as an inclinometer to obtain the azimuth and dip of the cylindrical samples. Three cores were drilled per level.

Each core was cut into 2 cm-long specimens for subsequent palaeomagnetic and rockmagnetic measurements at the PALEVOPRIM laboratory of Poitiers University. A JR-6 spinner magnetometer (AGICO) placed in a shielded room was used to measure natural remanent magnetisation. Samples were subjected to progressive AF ranging from 4 to 50 mT in 2–10 mT steps, and thermal demagnetisation was performed using an MMTD80 thermal demagnetiser.

Orthogonal demagnetisation diagrams (Zijderveld, 1967) and equal-
area stereographic projections for demagnetisation trajectories were
used to interpret the result of the demagnetisation process (Supp
data). The Remasoft software was used to analyse the data (Chadima
and Hrouda, 2006). In each case, the component directions were estab-
lished. Principal components analysis (Kirschvink, 1980) was used to
determine the directions of components. The mean directions of the
characteristic components were calculated after tilt correction by the
Fisher statistics (Fisher, 1953) and plotted on stereographic diagrams
(Supp data). The presence of a dual-polarity ChRM component with
means that are almost antipodal is an indication of the primary nature
of the isolated components. To create a local magnetic polarity stratiga-
phy, the palaeolatitude of the virtual geomagnetic pole (VGP) has been
calculated using the ChRM directions with maximum angular deviation
(MAD) of ≤15°. The VGP is plotted versus the stratigraphical position
(Fig. 2).

3.4. Geochemistry

A total of 152 samples were collected in the SDV-A, B, C, and D sed-
imentological sections (Figs. 1–2). Carbon isotope analyses on dispersed
organic matter (δ¹³C<sub>org</sub>) were performed on 143 samples (106 from
SDV-A and B sections, 14 from SDV-C section, and 23 samples from
SDV-D section; Table 4). Samples not considered for analyses have too
low carbon content, and/or major traces of modern roots, and/or deep
oxidation/weathering, preventing robust isotopic analyses. Organic
matter of the rocks was isolated, following the procedure described in
Yans et al. (2010) and refined by Storme et al. (2012). The dispersed or-
ganic carbon isotope analyses (δ¹³C<sub>org</sub>) are based on powdered rock
samples of about 3 to 10 g, acidified in 25 % HCl solution during 2 h in
order to remove carbonate. Soluble salts were removed by repetitive
(1–6) centrifuging (4000 rpm) with deionised water until a neutral sed-
iment was obtained. Finally, residues were dried at 35 °C and powdered
again. Analyses were performed with an elemental analyser (Carlo-Erba
1110) connected online to a ThermoFinnigan Delta V Plus mass
spectrometer at the University of Erlangen (Germany). Accuracy and
reproducibility of the analyses were checked by replicate analyses of

international standards USGS40 and USGS41. The reproducibility of
analyses is within 0.2 ‰ (1σ). The CaCO₃ (%) content of the samples
was measured with a Bernard Calcimeter (Table 4).

3.5. Abbreviations

**MP**, Mammal Paleogene reference level: this European biochronological scale differs from others (e.g., North American Biochron) as it corresponds to the time of deposit of one locality and not a biochron (see Sigé and Legendre, 1997). Therefore, when comparing with other localities, we indicated the putative proximity with one or other level. As the number of localities has increased since the scale setting (Schmidt-Kittler et al., 1987), we now position some of them in intervals between two MPs that we note [MP10–MP11], including both MP levels, or [MP10–MP11], excluding both MP levels. **CENOGRID**: Cenozoic Global Reference benthic foraminifer carbon and oxygen Isotope Dataset from Westerhold et al. (2020). **GTS 2020**: Geological Time Scale from Speijer et al. (2020). **Wx**: Dinoflagellate cyst zone in Paris Basin (Brinkhuis and Biffi, 1993); **Dx**: Dinoflagellate cyst zone in Northwestern Europe (Speijer et al., 2020); **NPx**: Calcareous nanofossil zone (Speijer et al., 2020). **L**, maximal mesio-distal length in mm; **W**, maximal labio-lingual width in mm; **n**, number of specimens. **MNHN**, Museum National d'Histoire Naturelle, Paris; **UK**, Geiseltal-Unterkohle (reference level MP11); **uMK**, Geiseltal-Untere Mittelkohle (reference level MP12); **oMK**, Geiseltal-Obere Mittelkohle (reference level MP13); **OHM**, Geiseltal Oberes Hauptmittel (referred to MP14); **OK**, Geiseltal Oberkhole (referred to MP14); **UM**, University of Montpellier; **UM-PLG**, Plagnol collection; **UM-PLD**, Plantade collection; **UM-CLR**, Coulondres collection; **UM-LLN**, Le Lien collection. **LOD**: Last Occurrence Datum, last stratigraphical occurrence of a taxon, considered to have been synchronous over a specified geographic region. **FOD**: First Occurrence Datum, first stratigraphical occurrence of a taxon, over a specified geographic region.

4. Results

4.1. Sedimentary and stratigraphical characterisation

The sedimentary succession in which the fossiliferous localities are
found has been studied in detail, using the historically established
subdivided lithological units. This subdivision corresponds to informal
stratigraphical packages but which have regional reach. The succession
characterisation is based on the sedimentological logs in Figure 2B, and
then divided into 3 lithological units vertically from the base to the top
of the studied section: i) a lower silt-dominated unit, ii) a middle
lignite-rich unit and iii) a thick upper limestone-dominated unit.
These three units have good lateral extensions, which have made it pos-
sible to correlate them using physical bed correlation on field and satel-
lite images over the entire study area (Fig. 1B). Further study at a
regional level will allow this succession to be formalised in a nomencla-
ture of formations and members, but this is premature.

The lower silt-dominated unit begins at the base with a 5 metre-
thick first layer. This layer shows a sequence composed of metre-scale
limestone beds including algal debris and pseudomicrokarst facies
(sensu Plaziat and Freytet, 1978; Alonso Zarza et al., 1992). These beds
are overlain by freshwater-gastropod (dominated by Planorbis
pseudoammonius) rich wackestone in centimetric-scale beds, including
PLG locality, then topped by 5 m thick grey to white marls. This basal
layer is interpreted as palustrine to limited lateral extension shallow-
lacustrine depositional settings (Alonso-Zarza and Tanner, 2010).
Above, the second part of the lower silt-dominated unit corresponds
to a 50 to 60 m thick succession composed of alternating thick reddish
argillaceous silty to marly layers and infra metric-thick sandstone and
limestone beds (Fig. 2A). Sandstone beds are lenticular and show a
basal erosional surface followed by a deposit showing fining-up in
grain-size. Because of their size and context, they are interpreted as
ephemeral channel bodies (Miall, 1996). Limestone beds are dominated by mudstone facies showing locally rootlet traces. These beds correspond either to calcrete or to palustrine to lacustrine deposits (Alonso-Zarza and Tanner, 2010), the latter likely representing interfluve lakes or pond environments with limited lateral extension. The intercalated thick layers of red, orange to pink silty deposits show pedogenetic evidence, with root traces and marmorisation processes. They are interpreted as floodplain environments (Bridge, 2003).

The middle lignite-rich unit is greyer than the lower unit (Fig. 2H). It is composed of alternating i) fining-up metre-thick lenticular channelised sandstone beds, ii) centimetric to metre-thick limestone beds including oogones of charophytes and *Celtis* seeds and/or algal debris and/or freshwater-gastropods (dominated by *Planorbis pseudoammonius*), and showing rootlet traces locally, and iii) centimetre to metre-thick marly to silty brownish to greyish layers including degraded organic matter and which can sometimes be considered as lignites. The LLN locality is included in these latter facies. The depositional environment of this middle unit is interpreted as a marshy plain with channels (Allen, 1983), peat bogs and small, more oxygenated palustrine to lacustrine domains in which the limestones are formed (Alonso-Zarza and Tanner, 2010).

The thick upper limestone-dominated unit traditionally referred to *calcaires lutétiens* is here characterised by a first 40 m thick limestone succession, superimposed by 20 m thick silt-dominated deposits, passing up into a second thicker limestone. The first limestone succession is composed of mudstone to wackestone facies including algal debris, freshwater-gastropods (dominated by *Planorbis pseudoammonius* and *Lymnaea michelini*), rootlet traces, vadose silts in centimetric-scale cavities and pseudomicrokarst facies (*sensu* Plaziat and Frevtet, 1978; Alonso Zarza et al., 1992). Such deposits are interpreted as lacustrine to palustrine environments (Alonso-Zarza and Tanner, 2010) locally punctuated by contemporaneous events of karstification.

The characterisation of the vertical stratigraphical succession in Figure 2B, as well as the bed to bed correlation on the field and the geological mapping analysis (Fig. 1B), allows us to correlate the sedimentological section SDV-A with the sedimentological section SDV-D, including the Plantade (PLD) locality (Fig. 2E). The Plantade locality is thus included in the middle lignite-rich unit as the Le Lien (LLN) locality but is slightly lower stratigraphically. The Coulondres (CLR) historical locality could also be correlated in the same middle unit. The Plagnol (PLG) locality, included at the base of the lower silty-dominated unit, is therefore much lower stratigraphically (Fig. 2).

## 4.2. Palaeontology

Four localities have yielded mammalian remains together with Chelonian, Crocodylians, Aves, Pisces, Squamates and Lissamphibians. The aim of this section is to establish a mammalian faunal list and to compare it with other localities, in order to make approximate biostratigraphical correlations, and then to discuss mammalian evolution in a geochronological framework. Other vertebrates will be studied elsewhere.

### 4.2.1. The locality of Plagnol (PLG)

Plagnol has yielded few specimens and exclusively isolated teeth; with an overrepresentation of the metatherian genus *Peratherium* (n = 25/58). Ten mammalian taxa have been recovered from this limestone, most of them are relevant to the other coeval Montpellierian localities (Table 1).

#### 4.2.1.1. *Metatheria.* A single herpetotheriid metatherian species is present in Plagnol (n = 25). Only four of the available isolated dental specimens are complete and moderately worn (two dP3s and two M4s). The two dP3s UM-PLG-01 and UM-PLG-02 (L = 1.40, W = 1.23; Fig. 3A), similar in size to those of *Peratherium monspeliense* (Crochet, 1980, table 37), a species defined in Mas de Gimel (Crochet, 1979; Vianey-Liaud et al., 2024), have low stylar cusps C and D, which are subequal

<table><caption>**Table 1**

Faunal list of Plagnol (Les Matelles): 10 mammalian taxa for 51 mammalian remains.</caption><thead><tr><th>Order or higher rank</th><th>n</th><th>Family</th><th>n</th><th>Species</th><th>n</th></tr></thead><tbody><tr><td>Metatheria</td><td>26</td><td>Herpetotheriidae</td><td>25</td><td>Peratherium sp. 1</td><td>24</td></tr><tr><td>Eulipotyphla</td><td>2</td><td>Amphilemuridae</td><td>1</td><td>Macrocranion sp. sensu Russell et al., 1975</td><td>1</td></tr><tr><td>?Eulipotyphla</td><td>1</td><td>Nycittheriidae</td><td>1</td><td>Aff. Plagioctenoides sp.</td><td>1</td></tr><tr><td>Chiroptera</td><td>4</td><td>Icaronycteridae</td><td>3</td><td>"Icaronycteris menus"</td><td>3</td></tr><tr><td>Rodentia</td><td>15</td><td>Gliridae<br/>Euromyidae<br/>Theridomyoidea</td><td>1</td><td>Eogliravus sp.</td><td>1</td></tr><tr><td></td><td></td><td></td><td>4</td><td>Euromys woodi</td><td>4</td></tr><tr><td></td><td></td><td></td><td>9</td><td>Hartenbergeromys marandati</td><td>6</td></tr><tr><td>Artiodactyla</td><td>10</td><td>Diacodexeidae<br/>Haplobunodontidae</td><td>8</td><td>Diacodexis aff. varleti</td><td>8</td></tr><tr><td></td><td></td><td></td><td>2</td><td>Cuisitherium lydekkeri</td><td>2</td></tr><tr><td>Perissodactyla</td><td>1</td><td>Equoidea</td><td>1</td><td>Cf. Orolophus maldani</td><td>1</td></tr></tbody></table>

in height (Fig. 3A1). Relative heights of stylar cusps C and D show little intraspecific variation in several small 'opossum-like' lineages (e.g., Gernelle et al., 2024a, 2024b). Few other herpetotheriid dP3s are documented so far from French early Eocene localities. None of them have a configuration of stylar cusps C and D resembling that of the dP3 from Plagnol (note that the dP3 of the possibly coeval *P. matronense* is unknown). The dP3 of *Peratherium maximum* from Sézanne-Broyes (Crochet, 1980, fig. 105) exhibits high stylar cusps C and D, which are subequal in height, whereas the known dP3s of *Peratherium monspeliense* from Mas de Gimel and Saint-Clément-de-Rivière (Crochet, 1980: 202; see Coulondres and Le Lien below for further comparisons), have stylar cusp C lower than stylar cusp D. A fragmentary metastylar wing of a ?M3 with preserved stylar cusps C and D (UM-PLG-11) has these stylar cusps subequal in height, like on the two dP3s from Plagnol, thereby extending to various upper molariform loci the difference evidenced above between *Peratherium* from Plagnol and *P. monspeliense*. The left M4s UM-PLG-08 and UM-PLG-09 (L = 1.23, W = 1.94; Fig. 3E) have stylar cusp C which is lower than stylar cusps A and B in labial view (Fig. 3E1). In *P. matronense* from Avenay (Crochet, 1980, fig. 160), *P. monspeliense* from Mas de Gimel, its type locality, and A. *goethei* from Saint-Martin-de-Londres (middle Eocene?, Crochet et al., 1988, fig. 1), stylar cusp C of the M4 is subequal in height to stylar cusps A and B. A relatively low stylar cusp C compared to stylar cusps A and B, as in the M4 from Plagnol, is only known in the earliest Eocene *P. constans* from Dormaal (Ladevèze et al., 2012, fig. 5D) and in *P. maximum* from Sables de Brasles (Crochet, 1980, fig. 109; KG pers. obs.). However, the intraspecific variations of the relative stylar cusp heights of M4s of these herpetotheriid species are unknown. The small size of at least one molar (e.g., the fragmentary M1 UM-PLG-04) is only compatible with *P. matronense*, among middle to late Ypresian herpetotheriid species with known proportions (Crochet, 1980, table 24). Altogether, the material from Plagnol most likely represents a herpetotheriid species differing from those of Coulondres and Le Lien (but comparisons with similar small herpetotheriids assumed to be represented in the time range MP8 + 9-MP10, such as *P. matronense*, are difficult), which is provisionally referred to as *Peratherium* sp. 1.

#### 4.2.1.2. *Eulipotyphla.* A left m1 UM-PLG-29 (L = 2.98, W = 2.13; Fig. 4G) documents the amphilemurid "Macrocranion sp." (*sensu* Russell et al., 1975). In the Paris Basin, this species is rare in Avenay but more common in Condé-en Brie, Saint-Agnan and Prémontré (Russell et al., 1975; Louis and Laurain, 1983; Dégremont et al., 1985). This species was identified by rare specimens from Mas de Gimel, Naples, and Aumelas (Maitre et al., 2008; Vianey-Liaud et al., 2024). Lower molars of this relatively large species of *Macrocranion* differ from those of *M. tupaiodon* from Messel by lower and more swollen cuspidss (especially the metaconid), a shorter trigonid (the paracristid is more lingually oriented on m2), and a more mesiodistally extended entoconid (longer and higher entocristid). Interestingly, UM-PLG-29 represents the only known m1 for "Macrocranion sp."
A1

<figure><img src="image_3.png" /></figure>

B1

<figure><img src="image_4.png" /></figure>

C1

<figure><img src="image_5.png" /></figure>

D1

<figure><img src="image_6.png" /></figure>

E1

<figure><img src="image_7.png" /></figure>

A2

<figure><img src="image_8.png" /></figure>

B2

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C2

<figure><img src="image_10.png" /></figure>

D2

<figure><img src="image_11.png" /></figure>

E2

<figure><img src="image_12.png" /></figure>

F

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G

<figure><img src="image_14.png" /></figure>

H1

<figure><img src="image_15.png" /></figure>

I1

<figure><img src="image_16.png" /></figure>

K1

<figure><img src="image_17.png" /></figure>

J

<figure><img src="image_18.png" /></figure>

H2

<figure><img src="image_19.png" /></figure>

I2

<figure><img src="image_20.png" /></figure>

K2

<figure><img src="image_21.png" /></figure>

L1

<figure><img src="image_22.png" /></figure>

L2

<figure><img src="image_23.png" /></figure>

L3

<figure><img src="image_24.png" /></figure>
<figure><img src="image_25.png" /><figcaption>**Fig. 4.** Chiroptera, Apatotheria, Pantolestidae pantolestans, and Amphilemuridae eulipotyphlans from Plagnol, Coulondres and Le Lien (X-ray µCT surface reconstructions). A, Right dp4 of "Icaronycteris menui" (UM-PLG-32) in labial (A1) and occlusal (A2) reverse views; B, right p4 of "Icaronycteris menui" (UM-LLN-111) in occlusal (B1) and lingual (B2) reverse views; C, left M2 of "Icaronycteris menui" (UM-LLN-133) in occlusal view; D, right M1 of aff. *Ageina* sp. (UM-LLN-2) in occlusal view; E, left m1or2 of *?Buxolestes* sp. indet. (UM-LLN-29) in occlusal (E1) and labial (E2) views; F, DP4 of *Macrocranium* sp. (UM-LLN-4) in occlusal (F1) and lingual (F2) views; G, m1 of *Macrocranium* sp. (UM-PLG-29) in occlusal (G1) and labial (G2) views; H, m2 of *Macrocranium* sp. (UM-LLN-5) in occlusal (H1) and labial (H2) views; I, left M2 of *Heterohyus* sp. (UM-CLR-103) in occlusal view; J, left M1or2 of *Gesneropithex* sp. (UM-LLN-42) in occlusal view; K, right M1or2 of *Gesneropithex* sp. (UM-LLN-52) in occlusal reverse view. Scale bars equal 1 mm.</figcaption></figure>

<caption>**Fig. 3.** Metatheria and Nyctitheriidae ?eulipotyphlans from Plagnol, Coulondres and Le Lien (X-ray µCT surface reconstructions). A, Right dP3 of *Peratherium* sp. 1 (UM-PLG-02) in labial (A1) and occlusal (A2) views; B, right dP3 of *P. monspeliense* (UM-CLR-09) in labial (B1) and occlusal (B2) views; C, left dP3 of *P. monspeliense* (UM-LLN-98) in labial (C1) and occlusal (C2) reversed views; D, left M2 of *Peratherium* sp. 2 (UM-LLN-96) in labial (D1) and occlusal (D2) views; E, left M4 of *Peratherium* sp. 1 (UM-PLG-09) in labial (E1) and occlusal (E2) views; F, left M1 of *P. monspeliense* (UM-CLR-06) in occlusal reverse view; G, right M1 of *P. monspeliense* (UM-CLR-05) in occlusal view; H, right m1or2 of aff. *Plagioctenoides* sp. (UM-CLR-105) in occlusal (H1) and labial (H2) views; I, right p4 of aff. *Plagioctenoides* sp. (UM-PLG-28) in occlusal (I1) and lingual (I2) views; J, left M1or2 of aff. *Plagioctenoides* sp. (UM-MGL-146) in occlusal view; K, right p4 of aff. *Pontifactor* sp. (UM-CLR-107) in occlusal (K1) and labial (K2) views; L, mandibular fragment with m2-3 and talonid of m1 of Nyctitheriidae gen. indet. (UM-LLN-06) in labial (L1), lingual (L2), and occlusal (L3) views. Scale bars equal 1 mm.</caption>
4.2.1.3. ?Eulipotyphla. A ?eulipotyphlan mammal is represented by a nyctitheriid, documented by the right p4 UM-PLG-28 (L ≥ 1.26. W = 0.77; Fig. 31). This tooth is characteristic of the family by its very small size, sectorial cusps, and a submolariform tricuspate trigonid, in which the paraconid is distinct and mesiolingual to the tall protoconid

and the metaconid is very slightly distal to the protoconid. The talonid is wide; the ectoflexid is deep and very mesiodistally extended; the sharp and tall cristid obliqua ascends to the summit of the metaconid; and the hypoconid constitutes the single prominent cusp of the talonid. The very peculiar morphology of the cristid obliqua evokes

<figure><img src="image_26.png" /><figcaption>**Fig. 5.** Primates and Paroxyclaenidae pantolestans from Coulondres, Plantade and Le Lien (X-ray µCT surface reconstructions). A, Right P4 of *Nannopithex zuccolae* (UM-CLR-125) in occlusal (A1) and lingual (A2) views; B, right p4 of *Nannopithex zuccolae* (UM-CLR-123) in occlusal (B1) and lingual (B2) views; C, right dp4 of *Nannopithex zuccolae* (UM-LLN-74) in occlusal (C1) and lingual (C2) views; D, right P4 of cf. *Protoadapis curvicuspids* (UM-CLR-142) in occlusal (D1) and mesial (D2) views; E, left P4 of Cercamoniinae gen. indet. (UM-LLN-34) in occlusal (E1) and mesial (E2) views; F, left mandible with m1–2 of *Paraspaniella gunnelli* (UM-PLD-01) in occlusal (F1 and F2) and labial (F3) views; scale bars equal 1 mm for A–E, 2 mm for F1, and 5 mm for F2–F3.</figcaption></figure>
Plagioctenoides and Wyonycteris. Plagioctenoides is a strict North American genus whereas Wyonycteris occurs in Euramerica; both genera are from late Paleocene–early Eocene series (Rose et al., 2012; Jones and Beard, 2023). In Europe, Wyonycteris is only known from earliest Eocene localities (Dormaal and Croydon; Smith and Smith, 1996; Hooker, 2018; note that we here follow the consensus view that Dormaal is earliest Eocene in age not latest Paleocene, e.g., Solé et al., 2016). Differences between these two placentinentans are so tenuous that it was considered that Plagioctenoides may be a senior synonym of Wyonycteris (Rose et al., 2012). Considering the type-species (P. microlestes and W. chalix), rare differences concern the p4. Plagioctenoides microlestes has a relatively larger, more inflated p4 trigonid and a smaller, less molariform p4 talonid (the entoconid and hypoconulid are weakly developed to indistinct). As a result, because of the simplicity of the talonid of UM-PLG-28, we attribute this specimen to aff. Plagioctenoides sp. On upper molars, Plagioctenoides and Wyonycteris also share several characters, especially a mesostyle and dilambdodonty. Interestingly, we recently identified from Mas de Gimel such a morphology on the minute-sized upper molar UM-MGL-146 (this specimen was not mentioned in Vianey-Liaud et al., 2024; Fig. 3J). This M1or2 exhibits other classic nyctitheriid traits (acute cusps, low paraconule and metaconule, and small hypocone). Very few upper molars of Plagioctenoides are documented (Rose et al., 2012; Jones and Beard, 2023), and differences with Wyonycteris concern the reduction of the precingulum mesial to the protocone. In most Wyonycteris species, notably the type-species W. chalix, this structure is enlarged, often forming a pericone. Because of the occurrence of a tiny precingulum in UM-MGL-146 and compatible size with the p4 UM-PLG-28, we tentatively attribute both specimens to the same species, aff. Plagioctenoides sp. The occurrence of this new placentidentine species at Plagnol and Mas de Gimel (but also at Coulondres, see below) provides new arguments in favour of a small radiation of placentidentine nyctitheriids during the early Paleogene in Europe (Russell et al., 1973; Smith and Smith, 1996; Vianey-Liaud et al., 2024).

### 4.2.1.4. Chiroptera.
A small-sized species is represented by the right dp4 UM-PLG-32 (L = 1.28, W = 0.71; Fig. 4A), the left p4 UM-PLG-27 (L = 1.08, W = 0.8) and the left m3 UM-PLG-26 (L = 1.26, W = 0.8). The dp4 represents one of the very rare deciduous premolars reported for early bats (Russell et al., 1973; Sigé, 1991; Sigé et al., 1998). This tooth is molariform with well-differentiated cuspirids; the paraconid is lingually displaced, low in lateral view but well-developed in occlusal view; the talonid is wider than the trigonid and has a nyctalodont arrangement (= the postcristid directly connects to hypoconid to the hypoconulid without reaching the entoconid; the latter is isolated). Note however that the hypoconulid is not fully lingual and close to the entoconid as in the classic nyctalodonty. Regarding the other teeth, this species is characterised by a very prominent metaconid on p4, a well-developed paraconid on p4 and m3, and nyctalodonty on m3. This morphology indicates affinity with the Icaronycteridae. In Europe, this family was long only represented by "Icaronycteris menui" from Avenay and Mutigny (Russell et al., 1973; Smith et al., 2012), which appears to represent a mixed species sample (Hand et al., 2023). More recently, Vianey-Liaud et al. (2024) mentioned Icaronycteris sp. indet. from Naples and ?Icaronycteridae sp. indet. from Mas de Gimel. The latter, documented by a unique P4, is similar in size with "Icaronycteris menui" (Vianey-Liaud et al., 2024: 394). The same is true for the new p4 and m3 from Plagnol. Moreover, on the p4 UM-PLG-27, we note the presence of a lingual cingulum, which was considered as a synapomorphy of "I. menui" by Smith et al. (2012; see also Russell et al., 1973, fig. 1j). We thus propose that the small icaronycterid from the Montpellierian area (Mas de Gimel and Plagnol) belongs to "Icaronycteris menui". This hypothesis is strengthened by other specimens from Le Lien, including a very characteristic upper molar (see below).

### 4.2.1.5. Rodentia.
We are able to discriminate three rodent species within the 15 specimens recovered from Plagnol. One upper molar (M1 or M2) of a small Gliridae (UM-PLG-33; L = 1.02, W ~ 0.96; Fig. 6A) is attributed to *Eogliravus* sp. despite the fragmentary nature of the tooth. This genus was first mentioned from Mas de Gimel (Hartenberger, 1971). Eight specimens of *Hartenbergeromys marandati* are recognised due to a reduced hypocone and sinus, the presence of a disto-mesial elongated paraconule, an inflated metaconule, and a labially shifted mesostyle on M1 (UM-PLG-40; L = 1.71, W = 1.99; Fig. 6C). The specific attribution is due to small dimensions compared to *H. hautefeuillei* of Grauves, Saint-Agnan, Azillanet, and Prémontré. Four teeth belong to *Euromys woodi* (Fig. 6D-F) as indicated by the presence of granules and crestulid on enamel of the talonid basin of lower molars (UM-PLG-43; W = 3.15; Fig. 6D) and the lack of entolophid, as observed on teeth from Prémontré. The mesoconid is however larger than in the specimens from Prémontré. This species is well known from Pourcy, Avenay and Mutigny, and has some representatives in the localities of Saint-Agnan and Prémontré (Escarguel, 1999).

### 4.2.1.6. Artiodactyla.
Two right upper molars, UM-PLG-54 (W = 5.6; Fig. 8G) and UM-PLG-58 (L = 5.1) display a lingual metaconule, a large paracone, a small paraconule very close to a crescentic protocone, and slightly developed parastyle and mesostyle. Despite wear and broken parts, they undoubtedly belong to the genus *Cuisitherium*, well-known from the MP10 reference level of Grauves (Sudre and Lecomte, 2000). The dimensions of those specimens are quite similar to the width of M1s and length of M2s or M3s of *Cuisitherium lydekkeri* from Epernay, Monthelon, Cuis, Saint-Agnan, Grauves, Mas de Gimel and Naples (Sudre and Lecomte, 2000; Vianey-Liaud et al., 2024). We therefore attribute those remains to the species *Cuisitherium lydekkeri*.

Five specimens, including three lower molars, UM-PLG-49 (m2 trigonid; W = 2.7), UM-PLG-50, (m2; L = 3.8, W = 2.9; Fig. 8A) and UM-PLG-51 (possible m1; L = 3.4, W = 2.3), and two upper molars, UM-PLG-52 (M1; L = 3.8, W = 5.1) and UM-PLG-53 (M2; L = 4.7, W = 5.8; Fig. 8B), are characteristic of large European *Diacodexis* with developed disto-lingual cingulum, such as *Diacodexis varleti* described from Condé en Brie (Louis, 1996). Sudre et al. (1983) proposed slight differences between *D. varleti* and what they considered as a possible new taxon *D. cf. varleti* from Saint-Agnan and Sézanne-Broyes. The later species hereafter named *Diacodexis aff. varleti* (= *Diacodexis cf. varleti* n. sp. in Sudre et al., 1983, *D. cf. D. varleti* in Sudre and Erfurt, 1996, and *D. cf. varleti* in Erfurt and Sudre, 1996) differs from *D. varleti* by a rounded occlusal outline and slight lingual enlargement of upper molars (Fig. 8B), subequel paracone and metacone (whereas paracone is higher than metacone in Condé en Brie specimens), a larger size of M1 (but not of the M2), a more reduced paraconid which is closer to metaconid, a stronger entoconid with prominent mesial cristid and a thick distolabial cingulid (Fig. 8A). All these dental traits also characterise the species from Plagnol, which is thus attributed to *Diacodexis aff. varleti*. This species is also known from Saint-Agnan, Sézanne-Broyes, Cuis, Grauves, Monthelon, Mas de Gimel, Naples, Prémontré and Geiseltal UK. We also refer three premolars of *Diacodexeidae*: a right P4, UM-PLG-55 (L = 3.6, W = 3.8) with a narrow central protocone and large ectoloph close in size to Prémontré specimens (Sudre and Erfurt, 1996), a p2 or p3 UM-PLG-57 (L = 3.5, W = 1.3) with a simple morphology, and a left P2, UM-PLG-56 (L = 3.6, W = 1.8) similar in morphology but larger than *D. aff. antunesi* from Fordones (Boivin et al., 2018). Unfortunately, very few data for premolars of *D. aff. varleti* exist and only the large size is congruent with an attribution to *D. aff. varleti*.

### 4.2.1.7. Perissodactyla.
A unique lingual fragment of a right upper molar (UM-PLG-48; L > 6.2) belonging to a Perissodactyla has been found. This specimen, despite of wear, retains a thick lingual cingulum at protocone and in the central valley that tapers at hypocone level. This feature reminds us of a primitive Equoidea. It differs from
Hyracotherium leporinum, which displays a large protocone lingually extended (Bronnert and Métais, 2023). It is slightly larger than Cymbalophus hookeri from Palette (Godinot et al., 1987) and differs by higher cusps. It further differs from Pliolophus barnesi (Hooker, 2010; Bronnert and Métais, 2023) by a reduced cingulum bordering hypocone and lack of endostyle and of ectohypocrista. It is too small to be attributed to Propalaeotherium spp. (Rémy et al., 2019) or Hallensia spp. (Bronnert and Métais, 2023) and the cingulum is too thick, notably at hypocone, compared to Pachynolophus spp. Orolophus maldani, including Propachynolophus levei (Bronnert and Métais, 2023), better fits in size and morphology with the fragmentary specimen from Plagnol. Indeed, its M1 and M2 display equivalent cingulum development, with equivalent cusp height and similar upper molar length (L mean of 8.16 for n = 100 M1 + M2 of O. maldani, ranging from 7 to 9.5 mm; Bronnert and Métais, 2023). The perissodactyl form Plagnol could therefore correspond to a small M1 of cf. Orolophus maldani.

### 4.2.2. The locality of Plantade (PLD)

Only three specimens were collected in that locality, two pantolestans and a perissodactyl (Table 2).

#### 4.2.2.1. Pantolesta.
Two mandibles, UM-PLD-01 (left mandible with m1-m2; Fig. 5F) and UM-PLD-02 (right edentate mandible), are assigned to the Merialinae, a Paroxyclaenidae sub-family, characterised by close metaconid and paraconid on lower molars (Russell and Godinot, 1988; Solé et al., 2019). The fossils from Plantade are distinctly smaller than Spaniella carezi from Barranc de Forals in Spain (Crusafont-Pairó and Russell, 1967). Indeed, the m1 preserved on UM-PLD-01 (L = 4.4, W = 3.4) is as long as the m3 of Spaniella carezi, which is the paroxyclaenid species with the smallest molars. It also differs by more mesially-located paraconid, more reduced precingulid on m2, and narrower talonid. The molars on UM-PLD-01 are closely similar to those of Paraspaniella gunnelli from Prémontré and Grauves (Solé et al., 2019), as they share a short and wide talonid, high entocristid and entoconid, and a faint precingulid. The m1 and m2 (L = 3.7, W = 3.0) of UM-PLD-01 are very similar in size to those of P. gunnelli (Lm1 = 4.3; Lm2 = 3.7; Solé et al., 2019). Moreover, the L/W ratios of the m1 (1.3) and m2 (1.23) are close. The occurrence of such ratio values is a diagnostic feature of P. gunnelli, linked to the square-shaped morphology of the lower molars of this species. It can be noted that merionalines were more abundant than the paroxyclaenines during the Ypresian, but disappeared around the Ypresian-Lutetian boundary (Solé et al., 2019).

#### 4.2.2.2. Perissodactyla.
One right humerus of a large Perissodactyla (Fig. 9C; UM-PLD-03) displays a strong and low deltopectoral crest. Despite its weak preservation, we notice that the capitulum is not keeled and extends distally, further than the trochlea, and that the medial edge of the trochlea is sharp. These features are known in Lophiodon (Holbrook, 2009). Few humeri of Lophiodon have been described, but UM-PLD-03 appears to be smaller than specimens of L. leptorynchum from Aumelas (FL pers. obs.) and La Livinière (Holbrook, 2009) and is very close in size to L. cf. leptorynchum from Naples 2 (Vianey-Liaud et al., 2024; FL pers. obs.). We therefore propose the presence of L. cf. leptorynchum in Plantade as in Mas de Gimel/Naples, pending further element of comparison.

### 4.2.3. The locality of Coulondres (CLR)

#### 4.2.3.1. Metatheria.
Among metatherians from Coulondres (n = 32, including unpublished material; Table 2), two species of the herpetotheriid Peratherium were recognised by Crochet (1980), namely Peratherium matronense and P. monspeliense. Most of the specimens described represent P. monspeliense, a typical species of the Grauvian from southern France, which is documented elsewhere (Azillanet, Mas de Gimel, Saint-Clément-de-Rivière; Crochet, 1980; Marandat, 1986;

<caption>**Table 2**</caption>

Faunal list of Coulondres/Plantade (Saint-Gély-du-Fesc): 14 mammalian taxa for 81 mammalian remains.

<table><thead><tr><th>Order or higher rank</th><th>n</th><th>Family</th><th>n</th><th>Species</th><th>n</th></tr></thead><tbody><tr><td>Metatheria</td><td>32</td><td>Herpetotheriidae</td><td>31</td><td>Peratherium monspeliense</td><td>30</td></tr><tr><td></td><td></td><td>Peradectidae</td><td>1</td><td>Cf. Peradectes sp.</td><td>1</td></tr><tr><td>Apatotheria</td><td>1</td><td>Apatemyidae</td><td>1</td><td>Heterohyus sp.</td><td>1</td></tr><tr><td>Pantolesta</td><td>2</td><td>Paroxyclaenidae</td><td>2</td><td>Paraspaniella gunnelli</td><td>2</td></tr><tr><td>?Eulipotyphla</td><td>6</td><td>Nycittheriidae</td><td>5</td><td>Aff. Pontifactor sp.<br>Aff. Plagioctenoides sp.</td><td>3<br>2</td></tr><tr><td>Chiroptera</td><td>3</td><td>Indet</td><td>3</td><td>Indet.</td><td>3</td></tr><tr><td>Primates</td><td>7</td><td>Microchoeridae</td><td>4</td><td>Nannopithex zuccolae</td><td>4</td></tr><tr><td></td><td></td><td>Notharctidae</td><td>1</td><td>cf. Protoadapis curvicuspids</td><td>1</td></tr><tr><td>Rodentia</td><td>6</td><td>Indet</td><td>6</td><td>Lost (Hartenberger et al., 1969)</td><td>6</td></tr><tr><td>Carnivoraformes</td><td></td><td></td><td>2</td><td>Uintacyon cf. hookeri</td><td>2</td></tr><tr><td>Artiodactyla</td><td>1</td><td>Diacodexeidae</td><td>1</td><td>Diacodexis aff. varleti</td><td>1</td></tr><tr><td>Perissodactyla</td><td>2</td><td>Palaeotheriidae</td><td>1</td><td>cf. Pachynolophus livinierensis</td><td>1</td></tr><tr><td></td><td></td><td>Lophiodontidae</td><td>1</td><td>Lophiodon cf. leptorynchum</td><td>1</td></tr></tbody></table>

Vianey-Liaud et al., 2024). A single fragment of M1 (UM-CLR-06; W = 1.69; Fig. 3F) has been listed as *P. matronense* (Crochet, 1980, table 24), probably based on its smaller width than M1 of *P. monspeliense* (Crochet, 1980, table 24 vs. table 37). The only fragmentary M1 from Coulondres, attributed to *P. monspeliense* by Crochet (1980) (UM-CLR-05; L = 1.85; Fig. 3G; M2 is unknown for *P. monspeliense*), with a relatively small stylar cusp C, has in fact a wider stylar shelf with larger main cusps and stylar cusps than on UM-CLR-06 (Fig. 3F vs. Fig. 3G). We rather consider UM-CLR-06, with all herpetotheriid teeth from Coulondres, such as the fragmentary dP3 UM-CLR-09, also with a relatively small stylar cusp C (Fig. 3B1), included in the size variation of *P. monspeliense*. In fact, such a large upper molar size range is documented in other similarly-sized marsupialiforms (e.g., Ladevèze et al., 2012, fig. 4d-f). There is no valid record of *Peratherium matronense* from Coulondres.

One M2 (UM-CLR-01), illustrated elsewhere (Crochet, 1980, fig. 28), represents a putative peradectid metatherian, given that the protocone is much lower than the paracone in mesial view and that the centrocrista is nearly strait (see Gernelle et al., 2024a, table 6). UM-CLR-01 possibly belonged to an unnamed species already identified from Azillanet (by one M3; Marandat, 1986: pl. 1, fig. 2; Gernelle et al., 2024a) and from Mas de Gimel (by one labial fragment of M2; Vianey-Liaud et al., 2024, fig. 2; Gernelle et al., 2024a). It needs to be formally defined, waiting for more dental material. UM-CLR-01 is thus provisionally identified as cf. *Peradectes* sp. (differing from *Peradectes* sp. in Crochet, 1980, which contained specimens belonging to three *Peradectes* species; see Gernelle et al., 2024a).

#### 4.2.3.2. Apatotheria.
An apatemyid mammal is documented by the left M2 UM-CLR-103 (L = 2.79, W = 3.3; Fig. 4I). This sub-quadrate tooth with prominent styles, weak paraconule, and a large hypocone is attributed to *Heterohyus*. The molars of *Apatemys* are more transverse and triangular in outline, and they present a more pronounced bilobate labial border and a smaller hypocone. UM-CLR-103 documents a medium-sized *Heterohyus* species, intermediate in size between *H. gracilis* and *H. sudrei*. It is compatible in size with the lower molars of *Heterohyus* sp. recently described from Naples and Mas de Gimel (Vianey-Liaud et al., 2024) and it resembles the M2s of *Heterohyus* sp. from Grauves MNHN.F.GR.7652 and MNHN.F.GR.10015 (Russell et al., 1979). UM-CLR-103 and MNHN.F.GR.10015 further share a relatively high postprotocrista and a similar distal shortening of the crown between the metacone and the hypocone (Fig. 4I). These two molars certainly document the same species.

#### 4.2.3.3. ?Eulipotyphla.
?Eulipotyphlan mammals are represented by two nycittheriids. The species aff. *Plagioctenoides* sp. identified at Plagnol is documented by the right p4 UM-CLR-141 (W = 0.86) and the right
m1or2 UM-CLR-105 (L = 1.94, W > 0.76; Fig. 3H). The p4 is identical to that of Plagnol. It notably exhibits the very peculiar talonid morphology of *Plagioctenoides* (i.e., sharp and tall cristid obliqua, ascending to the summit of the metaconid). The lower molar is exodaenodont, has a lingually canted metaconid, a cristid obliqua that ascends the metaconid and has a deep ectoflexid. These characters are those of the placentidentines *Plagioctenoides* and *Wyonycteris*. Unfortunately, because the distal part of the talonid of UM-CLR-105 is broken away, we cannot check one of the main characters defining *Plagioctenoides* and *Wyonycteris*, namely the nyctalodont configuration of the molar talonid. As mentioned above, the differences between *Plagioctenoides* and *Wyonycteris* are weak. As for lower molars, the type species of these two genera only differ by the degree of exodaenodonty (*W. chalix* is more exodaenodont than *P. microlestes*). Viewing this character alone, UM-CLR-105, which is slightly exodaenodont, is more reminiscent of *Plagioctenoides* than of *Wyonycteris*, justifying our taxonomic assignment to aff. *Plagioctenoides* sp.

A second placentidentine nyctitheriid (n = 3) is attributed to aff. *Pontifactor* sp., which was recently mentioned from several Grauvian localities from southern France (Mas de Gimel, Naples, Azillanet, and La Rouyere; Vianey-Liaud et al., 2024). The specimens from Coulondres provide the morphology for P4 and p4 (UM-CLR-107; L = 1.52, W = 0.84; Fig. 3K). These loci are very similar to those of *Pontifactor*, *Plagioctenoides* and *Wyonycteris* by the tall cristid obliqua ascending the metaconid on p4, the reduced metacone, and the absence of postprotocrista on P4 (note however that p4 and P4 are respectively unknown for *Pontifactor* and *Plagioctenoides*). Molars of this taxon are twice as large as those of aff. *Plagioctenoides* sp. It evokes *Pontifactor* and differs from *Plagioctenoides* and *Wyonycteris* by a more advanced dilamdodonty (duplicated mesostyle).

### 4.2.3.4. Chiroptera.
This order is only documented by three fragmentary upper molars having lost their labial part (right M1or2s UM-CLR-108 and -114; and right M3 UM-CLR-140). They evoke by their minute size the small, probably new, palaeochiropterogygid species from Mas de Gimel and Naples (Vianey-Liaud et al., 2024). However, the specimens from Coulondres differ by a higher protocone, the presence of a paraconule, and the lack of lingual cingulum. Pending the recovery of more complete remains, this bat is left in open nomenclature as Chiroptera fam. indet.

### 4.2.3.5. Primates.
They are represented by two species. The microchoeroic *Nannopithex zuccolae* known from various Grauvian localities (Prémontré, Grauves, Saint-Agnan, Wittering Formation of the Bracklesham Group, Mas de Gimel and Naples; Godinot et al., 1992; Hooker, 1996b; Vianey-Liaud et al., 2024) is documented by four specimens. The right p4 UM-CLR-123 (L = 1.73, W = 1.18; Fig. 5B) is subrectangular and massive, with a high labial enamel wall, characteristic of the species. The right P4 UM-CLR-125 (L = 1.57, W = 2.24; Fig. 5A) documents a dental locus unknown at Mas de Gimel and Naples; it is identical with the P4s from the type-locality (Prémontré) (e.g., the lingual crest on the paracone is missing). Finally, the fragmentary left M1or2 UM-CLR-101 matches the diagnosis of the species in having neither postprotocone fold (also known as *Nannopithex* fold) nor hypocone.

A second primate species, documented by the right P4 UM-CLR-142 (L = 3.69, W = 5.0; Fig. 5D), represents a large species belonging to the *Protoadapis-Europolemur-Barnesia* group (sensu Godinot, 2015). The tooth is bicuspid and significantly wider than long, the enamel is slightly wrinkled, an enamel spur lingual to the postparacrista arises, the paracone is twice the height of the protocone, a short endoparacrista is present, a relatively high preprotocrista joins the mesial cingulum then connects the parastyle, a lower postprotocrista joins the distal cingulum near the lingual border of the crown, the parastyle and metastyle are labially displaced, the pre- and postparacristae are straight, and the labial cingulum is continuous. Comparisons of this P4 with those of

notharctids show that the labial position of the parastyle and metastyle, associated with the straight pre- and postparacristae and the occurrence of the enamel spur lingual to the postparacrista occur only on some unpublished specimens from Condé-en-Brie and Prémontré, which could document the problematic species *Protoadapis recticuspidens* (RT pers. obs.). This species is currently only known from its holotype MNHN. F.AL.5182, a fragmentary mandible with heavily worn m2-3 from the Ageian fauna (Lemoine, 1878). It was long considered a junior synonym of *P. curvicuspidens* (Russell et al., 1967; Szalay and Delson, 1979), but Schwartz and Tattersall (1989) noted similarities between *P. recticuspidens* and *Agerinia roselli*. Finally, in his reassessment of early cercamoniines, Godinot et al. (2018) listed this species as ?*Protoadapis recticuspidens*. The unique known P4 referred to as *Protoadapis curvicuspidens* (MNHN.F.Louis.128.Gr; Russell et al., 1967: 37) is unfortunately too worn to be properly compared with UM-CLR-142. However, both specimens are fully compatible in size (P4s of ? *Protoadapis recticuspidens* from Condé-en-Brie and Prémontré are smaller) and share the labial metastylar expansion. Conversely, the P4 UM-COS-77 of the recently described *Protoadapis andrei* (Cos, Quercy; Godinot et al., 2021) differs from UM-CLR-142 by numerous characters, such as a larger protocone and reduced parastyle and metastyle. Other *Protoadapis* species, notably those from the Geiseltal (uMK), are unknown by their P4. The same is true of the oldest *Europolemur* species, *Europolemur midiensis* (Rouzilhac, southern France) and ?*E. mancyi* (Mancy, Paris Basin) (Godinot et al., 2018). Regarding *E. kelleri* and *E. koenigswaldi* from Messel, which are documented by skulls, the occlusal surface of their P4 is unfortunately unknown, because the toothrows are preserved in occlusion. Finally, the P4s of *E. klatti* (Geiseltal, oMK to OHM) and *Barnesia hauboldi* (Geiseltal, oMK) differ from UM-CLR-142 by swollen paracone and metacone and reduced parastyle and metastyle. To conclude, the available data suggest that UM-CLR-142 documents a medium-sized primate close to *Protoadapis curvicuspidens*. Interestingly, this species may also be present at Mas de Gimel and Naples (Vianey-Liaud et al., 2024).

### 4.2.3.6. Rodentia.
Six specimens have been found and were compared to those from Mas de Gimel (Hartenberger et al., 1969, 1970). These authors considered Coulondres and Mas de Gimel to have the same age, based on the presence of the equivalent rodent species name "Microparamys sp. 2". Unfortunately, the material has been lost since that time, and we cannot proceed further with the systematic attribution of those remains. Indeed, the material of Microparamys has recently been attributed to different genera (Vianey-Liaud et al., 2019; Vianey-Liaud and Marivaux, 2021) and notably *Hartenbergeromys* and *Masillamys*, which are present in Mas de Gimel (*H. pailladensis* and *M. mattaueri* in Vianey-Liaud et al., 2024).

### 4.2.3.7. Carnivoraforms.
A left M3 (UM-CLR-100; L = 1.3, W = 2.5; Fig. 7B) of a carnivoraform recalls *Uintacyon hookeri* (Solé, 2014), but appears less transversely elongated than the type of this species (L = 1.4, W = 3.3; Solé, 2014). In the same way, the m1 UM-CLR-28 (Fig. 7A), with similar occlusal morphology to *Uintacyon hookeri*, is longer (L = 4.8, W = 3.6) than known m1 of this species (L = 4.2-4.5; Solé, 2014) but with similar width (W = 3.3-3.5; Solé, 2014). Considering a possible undescribed intraspecific variation, we refer the two specimens from Coulondres to *U. cf. hookeri*, as for those from Mas de Gimel. *Uintacyon hookeri* is known from Mutigny, Avenay, Condé-en-Brie, Brasles and Cuis (Solé, 2014).

### 4.2.3.8. Artiodactyla.
A talonid of a left m1or2 (UM-CLR-102; W = 2.7) attributed to *Diacodexis* displays the characteristic entoconid of the genus, with the mesial keel described in *D. aff. varleti* (see Fig. 8A). It is comprised within the size range of m1 and m2 of *D. aff. varleti* from Saint-Agnan and Sézanne-Broyes (Sudre et al., 1983).
### 4.2.3.9. Perissodactyla.
A talonid of a right dp3 UM-CLR-143 (W = 3.3; Fig. 8I) of a Palaeotheriidae which displays important space between metaconid and entoconid and a large distostylid, recalls the genus *Pachynolophus*. It differs from dp3 of *Cymbalophus hookeri*, on which the prehypocristid and preentocristid strongly converge, the entoconid is smaller than the hypoconid, the hypoconulid is never as developed, and width is shorter (W = 2.4–2.8; Godinot et al., 1987). UM-CLR-143 is far smaller than *Propalaeotherium gaudryi* (W mean = 5.4, W = 4.7–6; Bronnert and Métais, 2023) and *Pachynolophus ruscasseriensis* (W mean = 5.7; Rémy et al., 2019). The weak cingulid and the lack of clear junction between the hypolophid and hypoconulid exclude *Orolophus maldani* (W mean = 3.9, W = 3.2–4.1; Bronnert and Métais, 2023: Fig. 12j). *Pachynolophus eulaliensis* is more bunodont, with a more distal entoconid without distal cristid, a more distal hypolophid, and a smaller hypoconulid (W mean = 3.4, W = 3.3–3.5; Danilo et al., 2013). *Pachynolophus livinierensis* from La Livinière and Rouzilhac (Savage et al., 1965; Godinot et al., 2018) is also a small species and thus compares better in size to UM-CLR-143. Indeed, some unpublished new material of dp3 from Minervois of that species allows observing equivalent size, lophodonty and occlusal morphology to the specimen from Coulondres (FL pers. obs.), which we therefore attribute to *P. cf. livinierensis*.

### 4.2.4. The locality of Le Lien (LLN)

There are at least 22 mammalian taxa recognised on this locality with 165 numbered fossils (Table 3).

#### 4.2.4.1. Metatheria.
Three herpetotheriid species are recognised in Le Lien through fewer specimens (n = 15) than in Plagnol and Coulondres (with one herpetotheriid species each). *Peratherium monspeliense* is present as in Coulondres (n = 12). It is represented in Le Lien by isolated and fragmented M1 to M4 and m1 to m4, and the left dp3 UM-LLN-98 (W = 1.21; Fig. 3C), with an unpreserved stylar cusp A spur. This dp3 presents relatively high stylar cusp D and low stylar cusp C (Fig. 3C1), as in other dp3 known for *P. monspeliense* (Crochet, 1980, p. 202; see the fragmentary dp3 from Coulondres above), and corresponds in size (Crochet, 1980, table 37).

<table><caption>**Table 3**
Faunal list of Le Lien (Les Matelles): 22 mammalian taxa for 145 mammalian remains.</caption><thead><tr><th>Order or higher rank</th><th>n</th><th>Family</th><th>n</th><th>Species</th><th>n</th></tr></thead><tbody><tr><td>Metatheria</td><td>16</td><td>Herpetotheriidae</td><td>16</td><td>Peratherium monspeliense</td><td>12</td></tr><tr><td>Pantolesta</td><td>1</td><td>Pantolestidae</td><td>1</td><td>Peratherium sp. 2</td><td>2</td></tr><tr><td>Eulipotyphla</td><td>6</td><td>Amphilemuridae</td><td>6</td><td>Cf. Amphipetherium bastbergense</td><td>1</td></tr><tr><td>?Eulipotyphla</td><td>3</td><td>Nyctitheriidae</td><td>3</td><td>Aff. Pontifactor sp.</td><td>2</td></tr><tr><td>Chiroptera</td><td>18</td><td>Palaeochiropterygidae</td><td>3</td><td>Gen. sp. indet.</td><td>1</td></tr><tr><td></td><td></td><td></td><td></td><td>Gen. sp. ?nov</td><td>1</td></tr><tr><td></td><td></td><td></td><td></td><td>Palaeochiropteryx cf. tupaiodon</td><td>2</td></tr><tr><td></td><td></td><td>Icaronycteridae</td><td>4</td><td>"Icaronycteris menui"</td><td>2</td></tr><tr><td></td><td></td><td>Onychonycteridae</td><td>1</td><td>Aff. Ageina</td><td>1</td></tr><tr><td>Primates</td><td>12</td><td>Microchoeridae</td><td>1</td><td>Nannopithex zuccolae</td><td>2</td></tr><tr><td></td><td></td><td>Notharctidae</td><td>2</td><td>Cercamoniinae indet.</td><td>1</td></tr><tr><td>Rodentia</td><td>22</td><td>Gliridae</td><td>1</td><td>Eogliravus wildi</td><td>1</td></tr><tr><td></td><td></td><td>Theridomyoidea</td><td>18</td><td>Hartenbergeromys pailladensis</td><td>18</td></tr><tr><td>Hyaenodonta</td><td>3</td><td>Hyaenodontidae</td><td>2</td><td>Cynohyaenodon smithiae</td><td>1</td></tr><tr><td>Artiodactyla</td><td>18</td><td>Diacodexidae</td><td>5</td><td>Diacodexis aff. varleti</td><td>5</td></tr><tr><td></td><td></td><td>Dichobunidae</td><td>3</td><td>Protodichobune oweni</td><td>3</td></tr><tr><td></td><td></td><td>Haplobunodontidae</td><td>2</td><td>Cuisitherium cf. lydekkeri</td><td>2</td></tr><tr><td>Perissodactyla</td><td>15</td><td>Palaeotheriidae</td><td>5</td><td>Pachynolophus cf. livinierensis</td><td>3</td></tr><tr><td></td><td></td><td>Lophiodontidae</td><td>10</td><td>Lophiodon cf. leptorynchum</td><td>9</td></tr></tbody></table>

The left M2 UM-LLN-96 (L = 1.48, W = 1.47; Fig. 3D) and a worn left M3 (UM-LLN-131) are tentatively attributed to *Peratherium* sp. 2, still only recorded in Le Lien. Both specimens are significantly smaller than homologous molar loci of *P. monspeliense*. They exhibit a stylar cusp A which is not mesial to the paracingulum, a character so far considered diagnostic only of *P. matronense* among early Eocene herpetotheriids (Crochet, 1979: 373). However, the relative position of stylar cusp A is probably subject to intraspecific variation for a given upper molar locus (e.g., Ladevèze et al., 2012, fig. 5Gb vs. fig. 5Hb). UM-LLN-96 (Fig. 3D) is a M2, due to the depth of the ectoflexus and the relative length of the preparacrista. It has subequal length and width values, which is unusual so far for early Eocene herpetotheriid M2.

An isolated and worn left talon, with a rounded (typical of M1) procumbent protocone and a paraconule more labial than the metaconule (UM-LLN-64), belonged to the M1 of a herpetotheriid species larger than *P. monspeliense*, but smaller than the largest middle to late Ypresian European herpetotheriid, *P. maximum*. The length and shape of the protocone of this fragment evoke the M1 of *A. bastbergense*. A complete M1 from Naples has also been compared with this larger species (Vianey-Liaud et al., 2024), which is defined in Bouxwiller (MP13, Crochet, 1979). The advanced wear of this specimen prevents its unambiguous attribution, and it is hereafter listed as cf. *Amphiperatherium bastbergense*, as the specimen from Naples.

#### 4.2.4.2. Pantolesta.
A pantolestid is represented by the right m1or2 UM-LLN-29 (L = 4.80, W = 3.62; Fig. 4E). The four principal cusps are massive, the paraconid is median on the crown, reduced and close to the metaconid (resulting in a short trigonid), the trigonid/talonid height differential is low, the talonid is large, a preentocristid is present, and the entoconid is not distal but opposite to the hypoconid. This morphology is that of the European pantolestids *Premontrelestes* and *Buxolestes*. UM-LLN-29 is larger than *Premontrelestes duchaussoisi* from Prémontré (Smith, 2001), but is quite similar in size with *B. hammeli* from Bouxwiller (Jaeger, 1970) and cf. *Premontrelestes* sp. from Prémontré (Smith, 2001). On lower molars, there are few distinguishing characters between *Premontrelestes* and *Buxolestes* (p4, P4 and upper molars are more diagnostic; Smith, 2001: 28). However, the pantolestid from Le Lien is provisionally assigned to ?*Buxolestes* sp. indet. based on its large hypoconulid, moderate lingual orientation of the cristid obliqua, and high postcristid (Fig. 4E). Larger Grauvian species attributed to *Buxolestes* are present at Saint-Agnan and Mancy (Louis and Laurain, 1983) – but the specimens have never been figured – and from the Wittering Formation of the Bracklesham Group (Hooker, 1996b).

#### 4.2.4.3. Eulipotyphla.
The amphilemurid "Macrocranion sp." (sensu Russell et al., 1975) is documented by a left m2 (UM-LLN-5; L = 2.91, W = 2.31; Fig. 4H) and a right DP4 (UM-LLN-4; L = 2.93, W = 2.72; Fig. 4F), which document the only known deciduous premolar of this species. UM-LLN-4 resembles the DP4 of *M. vandebroeki* from Dormaal (Smith and Smith, 1995: 17) and *M. cf. nitens* from Avenay (Russell et al., 1975: 187) by a trapezoidal outline, a large mesially projected parastyle, well-separated paracone and metacone, and a mesiolingually displaced hypocone. It differs by lower and more swollen cusps and shorter metastylar lobe. The m2 UM-LLN-5 is identical to those of Naples (Vianey-Liaud et al., 2024) and Avenay (Russell et al., 1975).

A second amphilemurid is represented by the heavily corroded left M1or2 UM-LLN-42 (L > 1.64; W > 2.17; Fig. 4J) and the fragmentary right M1or2 UM-LLN-52 (Fig. 4K). These molars are essentially square in outline, the metastylar angle is blunt, the paraconule is reduced compared to the well-developed metaconule, the paracone and metacone are low and buccal, the hypocone is large, conical, and as far from protocone as metacone is from paracone, and an erinaceid crest (= prehypocrista) arises. This morphology matches that of the genus *Gesneropithex* (see Hooker, 1986: 224–225). *Amphilemur* and *Pholidocercus* have more trapezoidal M1–2 and a smaller hypocone
closer to protocone. *Macrocranion* differs by transverse M1-2, longer para- and metastylar lobes, and by sharper para- and metaconule cristae. *Gesneropithex* was known by late middle to late Eocene European species; the unique exception is *G. aumelasensis* from Aumelas (Maitre et al., 2008). This species is only documented by a lower mandible with m2-m3. Although a direct comparison is impossible, this species appears significantly larger than *Gesneropithex* sp. from Le Lien, which thus documents the oldest record of this genus.

4.2.4.4. ?Eulipotyphla. A minute species of a ?eulipotyphlan mammal is documented by a left mandible with preserved m2-m3 and the talonid of m1 (UM-LLN-06; Lm2 = 1.14, Wm2 = 0.83; Lm3 = 1.22, Wm3 = 0.85; Fig. 3L). The m2 is similar to the nyctitheriid molar from Coulondres attributed to aff. *Plagioctenoides* sp. by a crestiform paraconid, a lingually canted metaconid, subequal entoconid and hypoconid, a slight exodaenodonty and a deep ectoflexid. However, due to the complete corrosion of the enamel, the course of the cristid obliqua is hard to establish; we cannot confirm that this cristid ascends the metaconid as in *Plagioctenoides*; instead this cristid appears rather labial. Likewise, on the talonid of the m1-2, both the distolingual position of the hypoconulid and the nyctalodonty, which are characteristic of *Plagioctenoides*, remain uncertain on UM-LLN-06. However, judging the course of the postcristid on the talonid of the m2, the hypoconulid – if present – would be lingual as in *Plagioctenoides*. The m3 has a narrower but longer talonid than the m2, with a large and distally projected hypoconulid, which is centred on the distal margin of the talonid. Such an elongated m3, longer than m2, is rare among nyctitheriids. To our knowledge, this character only occurs in *Leptacodon choristus* (middle/late Paleocene, Wyoming) and *Saturninia carbonum* (Geiseltal OK). Given these peculiar characters and the uncertainties due to the complete corrosion of the enamel, UM-LLN-06 is attributed to an indeterminate nyctitheriid.

A second ?eulipotyphlan mammal is attributed to the placentineous nyctitheriid aff. *Pontifactor* sp. (n = 2). This species, discussed above (see Coulondres fauna), is here documented by two fragmentary left upper molars (UM-LLN-99 and -110).

4.2.4.5. *Chiroptera*. Bats are represented by four taxa. The minuscule Palaeochiropterygidae gen. et sp. ?nov. recently identified at Mas de Gimel and Naples (Vianey-Liaud et al., 2024) is documented by a left m3 (UM-LLN-93; L = 1.25, W = 0.79) identical to that of Mas de Gimel (UM-MGL-107; L = 1.23, W = 0.83). The very lingual direction of the family observed in these m3s are the very lingual direction of the cristid obliqua and the strong nyctalodonty, associated with the lingual position of the hypoconulid, distal to the entoconid (Hand and Sigé, 2018). Following Vianey-Liaud et al. (2024), the main differences of this m3 from that of other palaeochiropterygids are as follows: it differs from *Palaeochiropteryx tupaiodon* and *P. spiegeli* by its smaller size, less prominent and relatively lower cusps; it further differs from *Matthesia* by the lack of bulbous cusps; it is larger than *Microchiropteryx* and does not present the elongated and narrow crown that is characteristic of this genus; and finally, relative to *Stehlinia*, it differs from the oldest species *S. alia*, known from Aumelas (Maitre, 2014), by its smaller size and minor trigonid/talonid height difference.

A second palaeochiropterygid is represented by two unworn m1-2s attributed to *Palaeochiropteryx cf. tupaiodon* (left UM-LLN-3, L = 1.37, W = 0.97; right UM-LLN-95, L = 1.45, W = 1.03). A similar m1-2 was mentioned from Mas de Gimel (UM-MGL-449; L = 1.45, W = 1.0; Vianey-Liaud et al., 2024). These lower molars are comparable to those of *P. tupaiodon* from Messel but their dimensions fall below the smallest m1-2 attributed to this species (including the holotype HLMD 655-Me 25). Interestingly, Russell et al. (1973) also mentioned a species close to *Palaeochiropteryx tupaiodon* at Grauves based on the unfigured m1 MNHN.F.Gr.7558 (L = 1.3, W = 0.8). Although a direct comparison between this molar and those from the Montpellierian

area is impossible based on the literature, the very small size of the m1 from Grauves could indicate that it belongs instead to the previously discussed species, Palaeochiropterygidae gen et sp. ?nov.

The third bat is a small icaronycterid species attributed to "Icaronycteris menui". It is documented by the right p4 UM-LLN-111 (L = 1.09, W = 0.84; Fig. 4B) and the left M2 UM-LLN-133 (L = 1.33, W = 2.03; Fig. 4C). The p4 exhibits the distinctive characters of the species, already mentioned for UM-PLG-27 (see Plagnol fauna). The M2, which represents the unique known upper molar of this species in the Montpellierian area, is similar in size and morphology to the specimens from Mutigny and Avenay. Similarities are the long distolingually extended hypoconal lobe of the protocone, the centrocrista that reaches the labial margin, the absence of mesostyle, the prominent parastyle and metastyle separated by a deep ectoflexus, the narrow cingular shelf, the labially concave paracone and metacone, and the paracone lower than the metacone. The other characters observed on UM-LLN-133 are variable in "Icaronycteris menui". For instance, the continuous lingual cingulum without hypocone is present in MNHN.F.Louis.416.Mu (Russell et al., 1973, fig. 1b; Smith et al., 2012, fig. 2.3f), whereas other M1or2s may present a discontinuous cingulum (MNHN.F.Louis.369.Mu) or a cuspatc hypocone (MNHN.F. Louis.371.Mu). The variation of this structure strengthens the hypothesis that "Icaronycteris menui" from Mutigny and Avenay represents a mixed species sample (see Hand et al., 2023).

The fourth bat is documented by the right M1 UM-LLN-2 (L = 1.90, W = 2.47; Fig. 4D). This molar evokes an icaronycterid species by a continuous lingual cingulum and the presence of a cingular, small cuspatc hypocone on the long distolingually extended hypoconal lobe. However, the paracone and metacone are broad labially, the trigon basin is elongated (the crown thus appears relatively long mesiodistally), the centrocrista does not reach the labial border of the crown, the paraconule and metaconule are absent, and the postprotocrista connects directly to the base of metacone. All these characters, as well as the measurements, suggest that UM-LLN-2 could belong to *Ageina tobieni*, an onychonycterid species known until now only from Mutigny (Russell et al., 1973). UM-LLN-2 differs, however, from the rare published molars of *Ageina tobieni* by the presence of an incipient mesostyle on the labial cingulum, a deeper ectoflexus, and a higher and more cuspatc hypocone. Pending the recovery of further material, this bat is left in open nomenclature, as aff. *Ageina* sp.

4.2.4.6. *Primates*. Two species are recognised in Le Lien. The microchoerid *Nannopithex zuccolae* already mentioned at Coulondres is here represented by a left incomplete m1 (UM-LLN-51; W = 1.31) which is similar in shape and size to those described from the type locality of Prémontré (Godinot et al., 1992) or from Mas de Gimel and the Wittering Formation (Hooker, 1996b; Vianey-Liaud et al., 2024). More problematic is UM-LLN-74 (L = 1.76, W = 1.23; Fig. 5C), a moderately corroded right lower tooth which also evokes a m1 of *N. zuccolae* by a subterminal and procumbent paraconid, the absence of a hypoconulid, and the low postcristid. However, this tooth is small, below the size range of *N. zuccolae*, and displays striking differences from lower molars of that species: the trigonid is narrower, the metaconid is lower and more distally positioned, the cristid obliqua connects the top of the metaconid, and the entoconid is minute in lingual view (Fig. 5C2). This peculiar morphology indicates a dp4 that we attribute to *N. zuccolae*. Interestingly, the lingual orientation of the cristid obliqua ascends the metaconid also occurs in the dp4 of *Vectipithex*, a closely-related microchoerid genus (Hooker and Harrison, 2008).

The second species is represented by the left P4 UM-LLN-34 (L = 4.22, W = 4.98; Fig. 5E). This bicuspid tooth shares numerous characters with the P4 of cf. *Protoadapis curvicuspids* from Coulondres, such as a paracone twice as high as the protocone, a short endoparacrista, a relatively high preprotocrista that joins the mesial cingulum then connects the parastyle, a lower postprotocrista that joins the
<figure><img src="image_27.png" /><figcaption>**Fig. 6.** Rodents from Plagnol and Le Lien (X-ray µCT surface reconstructions; occlusal views). A, Right M1 or 2 of *Eogliravus* sp. (UM-PLG-33); B, left m1 of *Eogliravus wildi* (UM-LLN-24); C, right M1 of *Hartenbergeromys marandati* (UM-PLG-40); D, right m1 or m2 of *Euromys woodi* (UM-PLG-43); E, left DP4 of *Euromys woodi* (UM-PLG-44); F, right P4 of *Euromys woodi* (UM-PLG-45); G, left m2 of *Hartenbergeromys pailladensis* (UM-LLN-13); H, right M2 of *Hartenbergeromys pailladensis* (UM-LLN-15). Scale bars equal 1 mm.</figcaption></figure>

distal cingulum near the lingual border of the crown, and a continuous labial cingulum. However, it differs by a larger size, longer pre- and postparacristae, a smaller metastyle, and by a parastyle mesial to the paracone (not mesolabially displaced). Judging these disparities, we propose that UM-LLN-34 documents another species, provisionally attributed to a cercamoniine indet. Note that the p4s of *Protoadapis muechelnensis* and *P. ignoratus*, two species only documented by mandibles from the Geiseltal uMK (Thalmann, 1994) are compatible in size with UM-LLN-34.

4.2.4.7. *Rodentia.* The large majority of rodent teeth found in Le Lien belongs to the species *Hartenbergeromys pailladensis* (n = 18). This species recently described from Mas de Gimel (Vianey-Liaud et al., 2024), from the material previously assigned to *Hartenbergeromys cf. hautepeuillei* (Escarguel, 1999), differs from other species of the genus by more crested cusps and cuspids (e.g., m2 UM-LLN-13; L = 1.74, W = 1.63; Fig. 6G; M2 UM-LLN-15; L = 1.56, W = 1.63; Fig. 6H), the development of the pericingulum, and smaller metacone and hypocone. One left m1 (UM-LLN-24; L = 1.31, W = 1.26, Fig. 6B) is attributed to a Gliridae.

<figure><img src="image_28.png" /><figcaption>**Fig. 7.** Carnivoraforms from Coulondres and Le Lien (X-ray µCT surface reconstructions). A, Right m1 of *Uintacyon cf. hookeri* (UM-CLR-28) in lingual (A1) and occlusal (A2) views; B, left M3 of *Uintacyon cf. hookeri* (UM-CLR-100) in lingual (B1) and occlusal (B2) views; C, right dp4 of *Cynohyaenodon smithae* (UM-LLN-41) in occlusal view. Scale bars equal 1 mm.</figcaption></figure>
Considering its size, it is very similar to the specimens from Mas de Gimel and is thus attributed to *Eogliravus wildi*.

4.2.4.8. *Hyaenodonta*. Among three remains belonging to this order, only a right dp4 (UM-LLN-41; L = 3.4, W = 1.7; Fig. 7C) can be attributed to a species. This tooth displays the morphology of the dp4s reported for *Cynohyaenodon smithae* from Prémontré and is very close in size to these specimens (mean L = 3.9 ranging from 3.6 to 4.0 mm in Solé et al., 2021) being only slightly shorter. Length is an important trait that discriminates this species from the contemporaneous, morphologically close but longer hyaenodontid *Lesmesodon gunnelli* (Solé et al., 2021).

4.2.4.9. *Artiodactyla*. Two specimens can be attributed to *Cuisitherium lydekkeri*, namely a fragment of upper molar (UM-LLN-82) with a small paraconule and a lingual metaconule, and the left m3 UM-LLN-28 (L = 7.7, W = 4.7; Fig. 8H) with a well-developed hypoconulid

and selenodont labial cuspids. This later molar is close in size to the holotype from Epernay, the specimens from Mancy (Sudre and Lecomte, 2000) and Naples (Vianey-Liaud et al., 2024), and is only slightly larger than the two specimens from Grauves (Sudre and Lecomte, 2000).

Three fragmentary upper molars of *Protodichobune* are recognised. UM-LLN-31 is a left M1 (L = 4.4; Fig. 8F) without marked mesostyle, but with a bulbous labial margin with a large labial cingulum. The molar length is equivalent to specimens from Grauves (Sudre et al., 1983). Those fragments can be attributed to *Protodichobune oweni*, as *Protodichobune hellmundi* is markedly larger (based on lower molars only; Godinot et al., 2018).

Six specimens are referred to Diacodexeidae. A fragmentary upper molar (UM-LLN-129) displays a flat labial wall and a distally protruding metastyle, which is comparable in size with that of *Diacodexis*. We recognised a right P3 (UM-LLN-32; L = 3.3, W = 2.4) with size and

<figure><img src="image_29.png" /><figcaption>**Fig. 8.** Artiodactyls and perissodactyls from Plagnol, Coulondres and Le Lien (X-ray µCT surface reconstructions; occlusal view if not specified). A, Right m2 of *Diacodexis* aff. *varleti* (UM-PLG-50); B, right M2 of *Diacodexis* aff. *varleti* (UM-PLG-53); C, right p3 of *Diacodexis* aff. *varleti* (UM-LLN-39) in occlusal (C1) and lingual (C2) views; D, right p3 of *Diacodexis* aff. *varleti* (UM-LLN-86) in occlusal (D1) and lingual (D2) views; E, right calcaneus of *Diacodexis* aff. *varleti* (UM-LLN-123) in dorsal (E1), lateral (E2) and medial (E3) views; F, right molar of *Protodichobune oweni* (UM-LLN-31); G, upper right molar of *Cuisitherium lydekkeri* (UM-PLG-54); H, left m3 of *Cuisitherium lydekkeri* (UM-LLN-28); I, right dp3 of *Pachynolophus cf. livinierensis* (UM-CLR-143); J, right m1 of *Pachynolophus cf. livinierensis* (UM-LLN-27); K, left p4 of *Pachynolophus cf. livinierensis* (UM-LLN-26) in lingual (K1) and occlusal (K2) views; scale bars equal 1 mm except 10 mm for E.</figcaption></figure>
morphology equivalent to that of *D. aff. antunesi* from Fordones ]MP7-MP8 + 9[, southern France, or *D. sp.* from La Borie (~MP8 + 9, southern France; Boivin et al., 2018). Two narrow right p3s (UM-LLN-39; L = 4.4, W = 1.7; Fig. 8C; UM-LLN-86; L = 4.3, W = 1.6; Fig. 8D) slightly longer than that of *Diacodexis* from Fordones show a small paraconid, and a possible hypoconulid mesial to the distostylid. A p2 (UM-LLN-60; L = 3.0, W = 1.3) is larger than lower premolars of *D. antunesi* from Silveirhina (~MP7, Portugal), and only slightly larger than *D. cf. gigasei* from Palette (~MP7, southern France; Boivin et al., 2018). UM-LLN-123 is a left calcaneum (Fig. 8E) with a primitive artiodactyl morphology, similar to that of *Diacodexis* (i.e., presence of sustentacular projection, very deep lateral fossa and short calcaneal tuber; see Guthrie, 1968; Thewissen and Hussain, 1990; Kumar et al., 2010). The size of UM-LLN-123 (L = 21.3, W = 5.7, Depth = 9.1; Fig. 8E) is similar to that of the calcaneum attributed to *Diacodexis* (Kumar et al., 2010), which is intermediate in size between that of *Diacodexis metsiacus* from Wyoming, North America (L = 20.5-20.3) and cf. *Obotherium parvum* from Inner Mongolia, China (L = 21.8, W = 5.4, Depth = 8.1; Bai et al., 2023).

Unfortunately, premolars and postcrania of *D. varleti* and *D. aff. varleti* have never been described. Following size evolution of European Diacodexeidae, we refer the material from Le Lien to *D. aff. varleti*, as it corresponds to the largest known *Diacodexis* from Europe

and as it has already been described from geographically and stratigraphically close localities.

4.2.4.10. *Perissodactyla*. Five remains can be attributed to a small equoid taxon. First, a lower right molar, UM-LLN-27 (L = 8.7, W = 6.0), displays diagnostic features of *Pachynolophus* with twinned metaconid, large distostylid and well separated lingual cuspid (see Vianey-Liaud et al., 2024; Fig. 8J). Despite being within the size-range of the smallest m1 specimens of *P. ruscasseriensis*, it differs from this species by a more brachyodont condition. It better corresponds to a representative of small equoids, such as *P. livinierensis*, *P. eulaliensis*, or even *O. maldani*. However, the development of the cingulid is not as strong as in the two latter species (Danilo et al., 2013; Bronnert and Métais, 2023). The measurements of UM-LLN-27 are in the range of those of m1 and m2 of *P. livinierensis* from Rouzilhac and La Livinière (FLS2944 m2; L = 8.8, W = 5.7). UM-LLN-26 (L = 4.9, W = 3.5; Fig. 8K) is a biradiculate lower premolar (probably a p4 or p3) with a short trigonid, a metaconulid not twinned but slightly distal to the protoconid, and a cristid obliqua that reaches the postpropotocristid at midwidth of the tooth. The distostylid is large and there is no entoconid. This premolar is far too small to belong to *Propalaeotherium gaudryi*, and it is only slightly smaller than the p3 of *Orolophus* (L = 5.7-7, W = 3.3-4.8; Bronnert and Métais, 2023). It differs from the latter by the

<figure><img src="image_30.png" /><figcaption>**Fig. 9.** *Lophiodon cf. leptorynchum* from Plantade and Le Lien (photography). A, Right M3 of (UM-LLN-30); B, right fragmentary mandible with p4–m2 (UM-LLN-123) in dorsal (B1) and medial (B2) views; C, distal part of right humerus (UM-PLD-03) in posterior (C1) and anterior (C2) views; D, proximal part of right radius (UM-LLN-114) in posterior (D1) and anterior (D2) views. Scale bars equal 10 mm for A and 50 mm for B–D.</figcaption></figure>
development of a central distostyliid and a distal development of the
metaconid. It more probably belongs to a small *Pachynolophus*, smaller
than *P. ruscasseriensis*. UM-LLN-26 is compatible in size and morphology
with the lower molar UM-LLN-27 and can be interpreted as
*P. livinierensis*, even if it is slightly shorter than lower premolars from
Rouzilhac (p4 L = 5.9-7.1, W = 3.2-5.3; p3 L = 5.7-7.0, W = 3.1-
3.8; Godinot et al., 2018) or than FSL2944 from La Livinière (p4 L =
5.9, W = 4.1). Differences in length and width could be due to the
very rounded aspect of UM-LLN-26 and its broken distolabial part.
Then, a fragment of left upper molar, UM-LLN-36 (L = 7.75), with an
extended distal cingulum and a blunt metaconule, is reminiscent of
a *Pachynolophus*. It is not mesiodistally compressed, as the small
*Pachynolophus duvali* from the *Calcaire Grossier* of Passy. It is of the
size of a M1 or a small M2 of a small equoid, and thus clearly differs
from *Propalaeotherium* and large *Pachynolophus*. UM-LLN-36 shows
more similarities with *P. livinierensis* (e.g., L M1 holotype = 7.2; L M1
Rouzilhac = 7.9-8.7; Godinot et al., 2018) or even to *P. eulaliensis*
(L M1 = 6.1-7.6; L M2 = 7.7-8.9; Danilo et al., 2013).

We therefore conclude that these three specimens (and even a small
upper canine and a trigonid of lower molar) could be attributed to *P*. cf.
*livinierensis*. Representatives of this species are from Rouzilhac and La
Livinière, and some of them have been quoted from Grauvian localities
of the Paris Basin (Cuis, Grauves, Monthelon, Mancy, Saint-Agnan;
Godinot et al., 2018).

Ten specimens are assigned to a large Perissodactyla of the family Lophiodontidae. A large lower mandibular fragment with lophodont molars and a symphysis reaching the p4 clearly indicates the genus *Lophiodon* (Fig. 9B; Vautrin et al., 2020). An upper right M3 (UM-LLN-30; L = 27.3, W = 30.7; Fig. 9A) displays the characteristic triangular outline of *L. leptorynchum*, with thin cingula. It is the size of *L*. cf. *leptorynchum* from Naples (M3 UM-NAP-108; L = 26.2, W = 30.4; Vianey-Liaud et al., 2024), Mas de Gimel (M3 UM-MGL-535; L = 26.7, W = 30.9) and Naples 2 (mean M3 L = 26.6, W = 30.9; Vautrin, 2019). A proximal part of a right radius (UM-LLN-114; Fig. 9D) fits with the distal epiphysis of the humerus found at Plantade. It displays a flat lateral ulnar facet considered to be autapomorphic of the genus *Lophiodon* within Perissodactyla (Fig. 9D; Holbrook, 2009). According to its size, we provisionally refer this material to *L*. cf. *leptorhynchum* waiting for a revision of late Ypresian lophiodontids.

## 4.3. Palaeomagnetic results

The low sample intensity sometimes makes interpretation
difficult. It concerns the lower levels of the Lien SDV-A section. The
magnetostratigraphy of this part (Fig. 2D) shows the normal, inter-
mediate, and reverse VGP latitudes.

- The first 5 m of the SDV-A section shows samples of normal and reverse polarity. The first level (samples 95-98, Supplementary data) is of reverse polarity, and the next level shows samples of normal and reverse polarity. At the height of 5 m, again, the level is of reverse polarity. The vector endpoint diagram (Supp. data) for samples from these horizons shows a clear separation between two magnetisation components. This part of the SDV-A section is dominated by samples of reverse polarity and assumes that is R1 polarity.

- Between 11 m and 115 m heights of the sedimentological SDV-A section, deposits are consistent of normal polarity N (Fig. 2D). Above this normal polarity and up to 142 m the reverse polarity R2 is represented by eight levels of SDV-A and SDV-B sections.

- The upper part of the sedimentological log (SDV-C section) shows a reverse polarity R2 in its lower part (Fig. 2D). Above these, the section continues with 15 m of normal polarity N2.

- Concerning the SDV-D section, all the samples are of normal polarity N1 (Fig. 2G).

## 4.4. Organic carbon isotope geochemistry results

Carbon isotopic values on dispersed organic matter (δ¹³Corg) range from -28.0 to -23.0 ‰ (Fig. 2C, F; Table 4). These data are in good agreement with the expected δ¹³C values of organics in the Eocene in southern France (see Yans et al., 2014; Noiret et al., 2016). The CaCO₃ contents of both the successions range from <1 % to 99 % (Fig. 2; Table 4), and the *Calcaire lutétien* of the upper unit logically shows very high CaCO₃ content (>95 %).

The δ¹³Corg curve of SDV-A-C sections (Fig. 2C) shows the following successive trends, from base to top:

- δ¹³Corg heavy values, around -23.5 ‰ at the base of the succession;

- negative δ¹³Corg trend, from -23.1 ‰ at 04 m to -26.7 ‰ at 12 m, the Plagnol level (PLG) being included at the beginning of this trend;

- relatively light values between -27.5 ‰ and -26.5 ‰, from 12 m to 28 m;

- long-term positive trend, from -27.5 ‰ at 28 m to values around -24.5 ‰ in the *calcaires lutétiens* (from ~120 m to ~148 m); two short-term isotopic excursions are clearly superimposed on this long-term trend: i) from ~78 m to ~87 m with minimal values of -26.9 ‰ at 78 m which is underlying a lignitic level correlated to the localities of Plantade (PLD) and Coulondres (CLR), and ii) from ~105 m to ~113 m with minimal values of -26.3 ‰ at 107 m, 3 m above the Lien level (LLN);

- short-term negative excursion from ~148 m to ~155 m with minimal values of -28.0 ‰ at 151 m;

- relatively negative δ¹³Corg trend in the uppermost part of the section, from -23.8 ‰ at 154 m to -26.1 ‰ at the top of the section.

The δ¹³Corg curve of the SDV-D section (Fig. 2F) shows relatively stable values (from -24.2 ‰ to -26 ‰) with a short-term negative excursion, from 14 m to 19 m including the Plantade fossiliferous level, with minimal δ¹³Corg values of -27.2 ‰ at 16 m.

# 5. Discussion

## 5.1. Dating

### 5.1.1. Biochronology

Comparisons of taxonomic occurrences first help to propose approx-
imate ages for the localities in the Montpellier area. We use the
European Mammal Paleogene (MP) timescale for which the reference
level faunas (MP8 + 9 Avenay, MP10 Grauves, and MP11 Geiseltal
UK; Schmidt-Kittler et al., 1987; Biochrom'97, 1997) have been up-
dated, and the most relevant/rich faunas correlated with these refer-
ence levels (Supp data).

The Plagnol fauna displays four taxa (3/10) that extend from MP8 + 9 localities to MP10 localities (*Macrocranion* sp. in Russell et al., 1975, "Icaronycteris menui", *Euromys woodi* and cf. *Orolophus maldani*; Supp data) and four taxa known only from MP10-related levels or with a FOD at MP10 (*Hartenbergeromys marandati*, *Diacodexis* aff. *varleti*, *Cuisitherium lydekkeri*, *Eogliravus*). The last two taxa are only known from Plagnol (*Peratherium* sp. 1) or from the Montpellier area (aff. *Plagioctenoides* sp.). With regard to the relative heights of the stylar cusps, *Peratherium* sp. 1 is more similar to *P. matronense* (Crochet, 1980) and therefore seems to be ancestral to *P. monspeliense* (Mas de Gimel, Coulondres and Le Lien; see stylar cusps C and D in Fig. 3A1 vs. Fig. 3B1, C1), suggesting a slight anteriority to the MP10 regional fauna. In accordance with its low stratigraphical position, Plagnol could represent an intermediate level between MP8 + 9 and MP10 faunas, with the presence of MP10 index taxa. In this respect, Plagnol can be considered as an equivalent of Saint-Agnan, which is mostly considered as the lowest level among the MP10-related faunas, and has been proposed to be stratigraphically intercalated between the *Sables*
<table><caption>**Table 4**
CaCO₃ content and isotopic value for geochemistry samples from the four studied sections.</caption><thead><tr><th>Sections</th><th>Samples</th><th>CaCO<sub>3</sub> (%)</th><th>∂<sup>13</sup>C<sub>org</sub> (‰ V-PDB)</th></tr></thead><tbody><tr><td rowspan="16">SDV-C</td><td>21 LNS 30B</td><td>80</td><td>-26,1</td></tr><tr><td>21 LNS 30</td><td>77</td><td>-25,2</td></tr><tr><td>21 LNS 29D</td><td>48</td><td>-23,9</td></tr><tr><td>21 LNS 29C</td><td>49</td><td>-25,5</td></tr><tr><td>21 LNS 29B</td><td>92</td><td>-25,6</td></tr><tr><td>21 LNS 29A2</td><td>46</td><td>-23,5</td></tr><tr><td>21 LNS 29A1</td><td>49</td><td>-23,8</td></tr><tr><td>21 LNS 29</td><td>45</td><td>-26,8</td></tr><tr><td>21 LNS 28G</td><td>5</td><td>-28</td></tr><tr><td>21 LNS 28F</td><td>5</td><td>-26,5</td></tr><tr><td>21 LNS 28E</td><td>46</td><td>-24,3</td></tr><tr><td>21 LNS 28D</td><td>28</td><td>-23,4</td></tr><tr><td>21 LNS 28C</td><td>53</td><td>-26,3</td></tr><tr><td>21 LNS 28B</td><td>52</td><td>-25,7</td></tr><tr><td>21 LNS 28</td><td>87</td><td>-23,6</td></tr><tr><td rowspan="20">SDV-B</td><td>20 LN 24</td><td>96</td><td>-24,7</td></tr><tr><td>20 LN 23</td><td>98</td><td>-23,7</td></tr><tr><td>20 LN 22</td><td>99</td><td>-24,4</td></tr><tr><td>20 LN 21</td><td>98</td><td>-25,0</td></tr><tr><td>20 LN 20</td><td>97</td><td>-25,8</td></tr><tr><td>20 LN 19</td><td>97</td><td>-23,8</td></tr><tr><td>20 LN 18</td><td>98</td><td>-24,6</td></tr><tr><td>20 LN 17</td><td>97</td><td>-24,7</td></tr><tr><td>20 LN 16</td><td>99</td><td>-24,9</td></tr><tr><td>20 LN 15</td><td>97</td><td>-24,6</td></tr><tr><td>20 LN 14</td><td>96</td><td>-24,0</td></tr><tr><td>20 LN 13</td><td>96</td><td>-24,6</td></tr><tr><td>20 LN 12</td><td>98</td><td>-23,7</td></tr><tr><td>20 LN 11</td><td>95</td><td>-23,5</td></tr><tr><td>20 LN 10</td><td>99</td><td>-23,5</td></tr><tr><td>20 LN 09</td><td>98</td><td>-24,7</td></tr><tr><td>20 LN 08</td><td>57</td><td>-25,0</td></tr><tr><td>20 LN 07</td><td>97</td><td>-23,5</td></tr><tr><td>20 LN 06</td><td>65</td><td>-23,0</td></tr><tr><td>20 LN 05</td><td>99</td><td>-23,9</td></tr><tr><td>20 LN 04</td><td>99</td><td>-24,6</td></tr><tr><td>20 LN 03</td><td>98</td><td>-24,9</td></tr><tr><td rowspan="19">SDV-D</td><td>20 LPD 23</td><td>98</td><td>-26,0</td></tr><tr><td>20 LPD 22</td><td>98</td><td>-25,3</td></tr><tr><td>20 LPD 21A</td><td>90</td><td>-25,4</td></tr><tr><td>20 LPD 21</td><td>92</td><td>-25,1</td></tr><tr><td>20 LPD 19</td><td>4</td><td>-25,3</td></tr><tr><td>20 LPD 18</td><td>62</td><td>-25,0</td></tr><tr><td>20 LPD 17</td><td>42</td><td>-24,8</td></tr><tr><td>20 LPD 16</td><td>91</td><td>-25,8</td></tr><tr><td>20 LPD 15</td><td>90</td><td>-25,7</td></tr><tr><td>20 LPD 14</td><td>12</td><td>-27,2</td></tr><tr><td>20 LPD 13</td><td>99</td><td>-25,9</td></tr><tr><td>20 LPD 12</td><td>94</td><td>-25,7</td></tr><tr><td>20 LPD 11</td><td>2</td><td>-26,9</td></tr><tr><td>20 LPD 10</td><td>75</td><td>-26,3</td></tr><tr><td>20 LPD 9</td><td>58</td><td>-25,2</td></tr><tr><td>20 LPD 8</td><td>28</td><td>-24,6</td></tr><tr><td>20 LPD 7</td><td>75</td><td>-25,6</td></tr><tr><td>20 LPD 6</td><td>60</td><td>-25,7</td></tr><tr><td>20 LPD 5</td><td>68</td><td>-25,0</td></tr><tr><td>20 LPD 4</td><td>52</td><td>-25,2</td></tr><tr><td>20 LPD 3</td><td>68</td><td>-25,9</td></tr><tr><td>20 LPD 2</td><td>61</td><td>-24,2</td></tr><tr><td>20 LPD 1</td><td>39</td><td>-25,3</td></tr><tr><td rowspan="16">SDV-A</td><td>17 LN 01</td><td>55</td><td>-26,4</td></tr><tr><td>21 LN 28I</td><td>95</td><td>-26,7</td></tr><tr><td>21 LN 28F</td><td>86</td><td>-24,7</td></tr><tr><td>21 LN 28D</td><td>69</td><td>-24,6</td></tr><tr><td>21 LN 28C</td><td>63</td><td>-25,1</td></tr><tr><td>21 LN 28B</td><td>56</td><td>-25,7</td></tr><tr><td>21 LN 28A</td><td>59</td><td>-24,9</td></tr><tr><td>20 LN 28</td><td>96</td><td>-25,3</td></tr><tr><td>20 LN 27</td><td>95</td><td>-23,5</td></tr><tr><td>20 LN 26</td><td>96</td><td>-23,1</td></tr><tr><td>20 LN 25</td><td>97</td><td>-23,3</td></tr><tr><td>20 LN 29</td><td>97</td><td>-24,2</td></tr><tr><td>17 LN 65</td><td>93</td><td>-24,9</td></tr><tr><td>17 LN 64</td><td>89</td><td>-24,0</td></tr><tr><td>17 LN 63</td><td>91</td><td>-24,0</td></tr></tbody></table>

<table><caption>**Table 4 (continued)**</caption><thead><tr><th>Sections</th><th>Samples</th><th>CaCO<sub>3</sub> (%)</th><th>∂<sup>13</sup>C<sub>org</sub> (‰ V-PDB)</th></tr></thead><tbody><tr><td rowspan="16">SDV-C</td><td>17 LN 62</td><td>90</td><td>-24,1</td></tr><tr><td>17 LN 61B</td><td>93</td><td>-24,8</td></tr><tr><td>17 LN 61A</td><td>88</td><td>-23,8</td></tr><tr><td>17 LN 60</td><td>92</td><td>-24,7</td></tr><tr><td>17 LN 59</td><td>89</td><td>-24,8</td></tr><tr><td>17 LN 58</td><td>97</td><td>-23,3</td></tr><tr><td>17 LN 57c</td><td>89</td><td>-24,0</td></tr><tr><td>17 LN 56</td><td>83</td><td>-24,1</td></tr><tr><td>17 LN 55</td><td>77</td><td>-25,7</td></tr><tr><td>17 LN 54</td><td>95</td><td>-24,6</td></tr><tr><td>17 LN 53</td><td>54</td><td>-24,6</td></tr><tr><td>17 LN 52</td><td>41</td><td>-24,3</td></tr><tr><td>17 LN 51</td><td>61</td><td>-25,3</td></tr><tr><td>17 LN 50</td><td>63</td><td>-26,3</td></tr><tr><td>17 LN 49</td><td>46</td><td>-24,8</td></tr><tr><td>17 LN 48</td><td>66</td><td>-26,0</td></tr><tr><td>17 LN 47 L3</td><td>9</td><td>-24,1</td></tr><tr><td>17 LN 46</td><td>42</td><td>-24,6</td></tr><tr><td>17 LN 45</td><td>87</td><td>-23,5</td></tr><tr><td>17 LN 44</td><td>96</td><td>-23,6</td></tr><tr><td>17 LN 43</td><td>70</td><td>-25,5</td></tr><tr><td>21 LN 42B</td><td>98</td><td>-24,4</td></tr><tr><td>21 LN 42A</td><td>56</td><td>-23,6</td></tr><tr><td>17 LN 42</td><td>94</td><td>-26,3</td></tr><tr><td>17 LN 41</td><td>&lt;1</td><td>-25,4</td></tr><tr><td>17 LN 40</td><td>28</td><td>-25,5</td></tr><tr><td>17 LN 39</td><td>64</td><td>-25,9</td></tr><tr><td>17 LN 38</td><td>48</td><td>-25,0</td></tr><tr><td>17 LN 37</td><td>36</td><td>-24,0</td></tr><tr><td>17 LN 36</td><td>64</td><td>-24,4</td></tr><tr><td>17 LN 35</td><td>90</td><td>-25,8</td></tr><tr><td>17 LN 34</td><td>8</td><td>-25,3</td></tr><tr><td>17 LN 32 A</td><td>18</td><td>-25,2</td></tr><tr><td>17 LN 33</td><td>20</td><td>-26,9</td></tr><tr><td>17 LN 32 B</td><td>&lt;1</td><td>-24,4</td></tr><tr><td>17 LN 31</td><td>56</td><td>-24,1</td></tr><tr><td>17 LN 30</td><td>60</td><td>-25,0</td></tr><tr><td>17 LN 29</td><td>65</td><td>-24,1</td></tr><tr><td>17 LN 28</td><td>56</td><td>-25,6</td></tr><tr><td>17 LN 27</td><td>57</td><td>-24,0</td></tr><tr><td>17 LN 26</td><td>50</td><td>-24,8</td></tr><tr><td>17 LN 25</td><td>61</td><td>-24,6</td></tr><tr><td>17 LN 24</td><td>71</td><td>-24,4</td></tr><tr><td>17 LN 23</td><td>48</td><td>-25,3</td></tr><tr><td>17 LN 22</td><td>78</td><td>-24,6</td></tr><tr><td>17 LN 21</td><td>51</td><td>-25,8</td></tr><tr><td>17 LN 20</td><td>67</td><td>-24,9</td></tr><tr><td>17 LN 19</td><td>58</td><td>-25,6</td></tr><tr><td>17 LN 18</td><td>69</td><td>-25,4</td></tr><tr><td>17 LN 17</td><td>82</td><td>-26,6</td></tr><tr><td>17 LN 16</td><td>52</td><td>-26,4</td></tr><tr><td>21 LN 12A</td><td>55</td><td>-26,0</td></tr><tr><td>21 LN 11A</td><td>69</td><td>-25,7</td></tr><tr><td>17 LN 14</td><td>73</td><td>-25,9</td></tr><tr><td>17 LN 13</td><td>52</td><td>-26,3</td></tr><tr><td>17 LN 12</td><td>62</td><td>-26,7</td></tr><tr><td>17 LN 11</td><td>74</td><td>-27,5</td></tr><tr><td>17 LN 10</td><td>47</td><td>-26,7</td></tr><tr><td>17 LN 09</td><td>61</td><td>-26,4</td></tr><tr><td>17 LN 08</td><td>42</td><td>-26,4</td></tr><tr><td>17 LN 07</td><td>62</td><td>-26,3</td></tr><tr><td>17 LN 06</td><td>43</td><td>-26,9</td></tr><tr><td>17 LN 05</td><td>65</td><td>-26,5</td></tr><tr><td>17 LN 04</td><td>70</td><td>-26,4</td></tr><tr><td>17 LN 03</td><td>66</td><td>-26,1</td></tr><tr><td>21 LN 02A</td><td>59</td><td>-27,2</td></tr><tr><td>17 LN 02</td><td>45</td><td>-26,4</td></tr><tr><td>21 LN 01A</td><td>59</td><td>-26,7</td></tr></tbody></table>

d'Avenay and the Sables de Cuise (Louis, 1996). Plagnol and Saint-Agnan share the presence of Cuisitherium lydekkeri, Diacodexis aff. varleti, Euromys woodi and Macrocranion sp. sensu Russell et al. (1975). The relative abundance of Diacodexis aff. varleti within the Artiodactyla (13 % of the specimens from Plagnol) may also indicate the antiquity of the site. However, it differs from Saint-Agnan in the absence of classical MP10-
indexes such as *Nannopithex*, *Eurodexis*, *Hyrachyus*, *Propalaeotherium* and *Protodichobune oweni*, which may be related to environmental or taphonomic bias, as pointed out by the low number of large mammals recovered from this site. The faunal composition of Plagnol differs considerably from that of the other Montpellierian localities, due to the lack of primates and the abundance of species not known from the other localities (*Euromys woodi*, *Hartenbergeromys marandati* and *Peratherium* sp. 1). The unique palaeotherii remains are more reminiscent of *Orolophus* or some other primitive form than the more recent *Propalaeotherium* or *Pachynolophus*. We thus propose that Plagnol could refer to the [MP8 + 9-MP10] interval.

Of the 14 mammalian taxa identified from Coulondres/Plantade (CLR/PLD), 11 are also known from Mas de Gimel/Naples (MGL/NAP) (Supp. data), eight are shared with Grauves and four with Prémontré. The taxon aff. *Plagioctenoides* sp. is known only from the Montpellier area and five taxa are known only from southern France. All taxa have an exclusive MP10 distribution, except *Uintacyon* cf. *hookeri* which is also known in MP8 + 9 localities (Solé, 2014), and *Diacodexis* aff. *varleti*, which is also mentioned in Unterkohle Geiseltal (MP11, Erfurt and Sudre, 1996). It should be noted that, except for cf. *Pachynolophus livinierensis* and *Lophiodon* cf. *leptopynchum* (species also described from Rouzilhac and/or La Livinière), all MP10 taxa are known exclusively from “MP10a” localities (see Vianey-Liaud et al., 2024). Unfortunately, the lost rodents cannot be compared, even though they were proposed to be similar to those from Mas de Gimel (Hartenberger et al., 1969). As a consequence, we propose that Coulondres/Plantade should be biostratigraphically related to the [MP10] level.

Of the 22 mammalian taxa recognised from Le Lien, 13 are also present in Mas de Gimel/Naples (Supp. data), i.e., about 60 % of the total fauna. Some taxa are also shared with Grauves (n = 7), Prémontré (n = 7), Saint-Agnan (n = 7), Coulondres (n = 6), and Plagnol (n = 5). The biostratigraphical dating of Le Lien (LLN) is therefore very closely related to that of Mas de Gimel/Naples. The latter has been considered as Late Ypresian, close to MP10 (Biochrom'97, 1997; Vianey-Liaud et al., 2024). As for Coulondres/Plantade, very few taxa from Le Lien have a temporal distribution exceeding MP10 (less than 30 % of the total fauna), namely: the possible *Amphiperatherium bastbergense* also described from Aumelas, in the [MP10-MP11] interval, Bouxwiller (~MP13) (Crochet, 1980), and even ~MP14 faunas (Sudre et al., 1990; Marandat et al., 1993); *Macrocranion* sp. (Russell et al., 1975) also known from MP8 + 9 localities and from Aumelas (Maitre et al., 2008); “*Icaronycteris menui*” (also known from MP8 + 9); *Palaeochiropteryx tupaiodon* first described from Messel (MP11); *Pachynolophus livinierensis* from Rouzilhac; and *Diacodexis* aff. *varleti* also known from Geiseltal UK. We did not find any taxa at Le Lien that have a distribution that does not include an MP10 locality. Four species are known only from southern France (*Peratherium monspeliense*, *Lophiodon* cf. *leptopynchum*, *Hartenbergeromys pailladensis* and a Palaeochiropterygidae indet.), and the weakly-documented *Peratherium* sp. 2 is known only from this locality. We therefore assume a correspondence with the MP10 reference level (see Supp data).

The three described faunas from the study site are all attributed to the Grauvian ELMA close to MP10, defined at Grauves. The large number of taxa common to the Coulondres/Plantade, Le Lien, and Mas de Gimel sites emphasises their close age. However, we highlighted a slight difference between Plagnol and Coulondres/Plantades plus Le Lien, which could be related to an age difference, similar to the one already mentioned between Saint-Agnan and Grauves. Plagnol could be older than the other localities (lower unit in Fig. 2) and probably intermediate between MP8 + 9 and MP10. Although this is validated by the low stratigraphical position of Plagnol in limestone deposits at the base of the lower silty-dominated unit, we must also consider a difference in the depositional environment of this locality compared to the other sites belonging to the lignitic beds (middle unit in Fig. 2), which may slightly bias our interpretation.

### 5.1.2. Integrated chronology

Considering that the ages of all faunas studied here are related to the MP10 reference level included in the ELMA Grauvian, which corresponds to the upper part of the Ypresian (Speijer et al., 2020), we propose that the positive trend of the $\delta^{13}C_{org}$ occurring during a normal palaeomagnetic period (N1 in Fig. 2) is that of chron C23n (Fig. 10), which is recorded during the EECO (Westerhold et al., 2018). This positive trend has already been demonstrated to be global and “*one of the more prominent Paleogene positive carbon isotope shifts*” (in Westerhold et al., 2018, p. 636). The locality of Plagnol, at the base of the sedimentological SDV-A section, is included in a reverse magnetic period. Taking into account the positive trend discussed just above and the absence of potential large hiatuses (e.g., unconformity, palaeosols) in this part of the section, the Plagnol site is included in C23r. It is therefore older than 51.737 Ma, which corresponds to the upper limit of the chron (sensu Westerhold et al., 2020). The Plagnol level is just above the heaviest $\delta^{13}C_{org}$ value proposed here to correlate with the positive maximum recorded in C23r, dated at 52.10 Ma. This maximum is prior to the C23rH2/M hyperthermal event (Fig. 10; Westerhold et al., 2020). As a result, we tentatively associate the $\delta^{13}C_{org}$ excursion recorded in the Plagnol fossiliferous locality with the onset of this hyperthermal event. The estimated age of the hyperthermal C23rH2/M is 51.97 Ma (Westerhold et al., 2020). Plagnol should therefore be comprised in the interval between the positive and negative events [52.10–51.97 Ma], giving an average age of 52.035 ± 0.065 Ma.

The lowermost part of the long positive trend in Westerhold et al. (2020) is coeval with the hyperthermal event C23n.2nH1/N, which is difficult to precisely locate on the compiled sections (Fig. 10). Another well-defined event is observed in the $\delta^{13}C_{org}$ curve within the positive trend of C23n. This event is located in the middle part of the positive trend and could represent the C23n.2nH2/O, dated at 51.23 Ma (Westerhold et al., 2020). The most negative value for this event corresponds to the lignitic bed just below the fossiliferous locality of Coulondres/Plantade (Fig. 10). An upper event is also observed above the $\delta^{13}C_{org}$ positive trend and just below the C22r/C23r reversal (50.76 Ma). This $\delta^{13}C_{org}$ negative excursion can be correlated with the C23n.1nH1/P hyperthermal event dated at 50.865 Ma (Westerhold et al., 2020). The fossiliferous locality of Le Lien is recorded at the onset of this event (Fig. 10). It is thus slightly older than the age of this hyperthermal and younger than the maximum positive value recorded at the very beginning of the event, dated at ~51 Ma (Westerhold et al., 2020). Unfortunately, the studied continental sedimentary succession does not record the very short reverse chron C23n.1r that should be present between O and P and that could have helped to refine the age of Le Lien. We can note that this chron has a very short duration and is missing in some marine sedimentary records even from ocean sediment cores (e.g., Rodríguez-Pintó et al., 2013; Lauretano et al., 2016; Galeotti et al., 2019). We propose an age for the Le Lien fossiliferous locality within the interval ~51–50.865 Ma [with an average age of 50.93 ± 0.07 Ma.

Our data do not allow us to distinguish hyperthermal events in the lower part of C22r, here considered as the interval between the hyperthermals Q to T [50.76–50.37 Ma]. The uppermost event recorded in this section is at the top of C22r (Fig. 10), and could be related to C22rH5/U dated at 49.95 Ma (Westerhold et al., 2020). This would imply that the lacustrine limestone sequence included at the base of the upper limestone-dominated unit just above the middle lignite-rich unit and known as the *calcaires lutétiens*, mostly considered to be Lutetian in age (e.g., Bonnet et al., 1971), should instead correspond to the upper part of the Ypresian (see also Luccisano et al., 2020).

### 5.1.3. Age comparisons

First attempts to estimate the numerical age of MP10 related faunas were made using the evolution of mean tooth size in phyletic lineages of different mammalian orders (Escarguel et al., 1997; Escarguel, 1999). This method proposed ages around 50 Ma for Grauves, other related
<figure><img src="image_31.png" /><figcaption>**Fig. 10.** Interpretations of the δ¹³Corg curve and palaeomagnetic polarity variations obtained in the continental depositional context from the Serre-de-Vias (SDV-A-D) area, by comparison with the composite record from multiple boreholes in Westerhold et al. (2020) for the middle to late Ypresian.</figcaption></figure>
localities from the Paris Basin, and Mas de Gimel. Neal (1996) also proposed an age for Grauves by correlation of the *Sable à Unios et Térédines* Fm. – by means of stratigraphical sequence analysis – with the D8 dinocyst zone (W6 local dinocyst zone), the NP12 nannoplankton zone and C23n (51.7–50.7 Ma in Speijer et al., 2020). This results in a slightly older estimated age than for the numerical age but it has not been retained in recent charts (Speijer et al., 2020). Hooker (1996b), describing fossils from the Bracklesham Group of southern England, correlated some depleted faunas with MP10 index taxa (*Nannopathex zuccolae*, *Hartenbergeromys marandati* and *Ailuravus michauxi*) from the Wittering Formation at Bracklesham bay (W14i and W15 beds) and Dummer's Copse (DC5iii bed), with the onset of C22r, near the NP12/NP13 transition. This is consistent with the age assigned to the MP10 faunas, but the author did not rule on PC6, a locality from Lee and Peel Common, with possible MP10 taxa in C23n.

More recently, two continental fossiliferous localities assigned to the MP10 level have been the subject of new geochronological investigations. The fauna from Azillanet, in southern France, which occurs in a long section from the Minervois (Noiret et al., 2016), records the $\delta^{13}C_{org}$ positive trend. This trend corresponds to that of the EECO, suggesting that Azillanet is located at the top of this trend, which ends approximately with the hyperthermal event C22rH3/S or C22rH4/T (Westerhold et al., 2020). Noiret et al. (2016) interpreted this age in the interval between the late biochron NP12 and early biochron NP13, corresponding to between the top of C23n and the beginning of C22r, most likely between 51 and 50.3 Ma. A second study was carried out on the Prémontré locality in northern France. This locality occurs in the *Sables de Prémontré* unit (Dégremont et al., 1985) and has yielded a well-diversified organic-walled microfossil assemblage that is assigned to the lower part of the D9 dinoflagellate cyst zone. Correlations with the Merelbeke Clay Member established by Steurbaut et al. (2016) allowed them to locate the Prémontré fossiliferous level at the base of NP13 in C22r, approximately between 50.4 and 50.3 million years ago.

These dates allow us to illustrate probable temporal extensions of 11 well-calibrated European localities of late Ypresian and early Lutetian (Fig. 11). Besides Azillanet, Prémontré, the three localities of the Bracklesham group, and those of the Montpellierian area (this study), we can propose ages for three other localities. First, the Saint Eulalie locality (~MP8 + 9; Danilo et al., 2013) lies within the "ETM3 interval" at the top of C24n and the base of C23r, between the C24n.2rH1/J and C23rH1/L hyperthermal events (Noiret et al., 2016; 53.26–52.46 Ma in Westerhold et al., 2020). Second, the Messel fossil levels (~MP11) from the Middle Messel Fm. were dated between 47.2 Ma and 47.6 Ma by recalculation of the $^{40}$Ar/$^{39}$Ar Messel basalt age and astronomical calibration based on the palynomorphs (Lenz et al., 2015; Kaboth-Bahr et al., 2024).

Finally, the Epernay Formation which includes Mutigny was first proposed as belonging to the W3 local dinocyst zone on the basis of the discovery of *Stenodinium meckelfeldense* (= W. meckelfeldense) by Gruas-Cavagnetto (1968, see Laurain et al., 1983). However, the distribution of this taxon encompasses the zone and only the lower occurrence determines the beginning of the zone. The formation was then attributed to the W4 (equivalent to D7b dinocyst zone) by Lecomte (1994) and Neal (1996). In fact, S. meckelfeldense became extinct during C23n/NP12 (Iakovleva, 2017), long after the proposed zone. Heilmann-Clausen (2018) found the presence of *Axiodinium lunare* (= W. lunaris) at the base of the Epernay Fm. and *Dracodinium cf. astra* (= W. astra) at the top of the formation. This indicates that the lowest age is the beginning of the *Stenodinium meckelfeldense* zone (W3), but may extend to the end of C24n.1r/end of NP11 (Iakovleva, 2017), the upper occurrence

of *Dr. astra* (W5). Thus, we infer a possible extension of the Epernay Formation at Saran plus Mont Bernon from 54.8 to 52.9 Ma. Mutigny is at the top of the Epernay Fm. and has already been proposed by Solé et al. (2011) between 54 and 52 Ma following Neal (1996) and Duprat (1997), i.e., within C24n. It has also yielded the charophyte *Peckichara piveteaui* (Riveline et al., 1996). The *Peckichara piveteaui* zone has been correlated with the top of the NP11 – top of the D7b – at least in the upper half of C24n (including C24n.2r and C24n.1r; Speijer et al., 2020). Briais et al. (2016) also proposed that the *Peckichara piveteaui* zone lies between W4 and W5, in the upper part of C24n. Considering the mammalian fauna of Mutigny, it seems that the locality could be contemporaneous to younger than the Fournes fauna (dated to mid NP11, post ETM2 and correlated with C24n.3n in Noiret et al., 2016). Indeed, even if it is a depleted fauna (Marandat, 1991), several taxa from Fournes are more primitive than those from Mutigny and are known only from older localities such as the proviverrine *Parvagula palulae* (also known from Palette and Fordones; Solé et al., 2015), *Cymbalophus hookeri* (described from Palette, Godinot et al., 1987), which is more primitive than *Cymbalophus* aff. *cuniculus* from Mutigny and Condé-en-Brie (Bronnert and Métais, 2023), and *Peradectes crocheti* (also known from Fordones, Rians, Meudon, Soissons and Sotteville sur mer; Gernelle et al., 2024a), which is considered to be ancestral to *P. louisi* from Mutigny. In addition, *Peratherium musivum* (also known from Le Clot, Soisson, Rians and Pourcy; Gernelle et al., 2024b) is not known from Mutigny whilst *P. maximum* from Mutigny is not present from Fournes or older localities (except Pourcy, but its age is discussed e.g., Cavelier, 1987) but is known from numerous younger localities (Supp data). Finally, only the paromomyid *Arcius fuscus*, which has its oldest known occurrence in Fournes, is also present in Mutigny (López-Torres and Silcox, 2018). We therefore consider that Mutigny should be included in the interval corresponding to the Fournes maximum age (top of C24n.3n) to the last occurrence of the dinoflagellate *Dr. astra* at the end of C24n.1r, thus between 53.4 and 52.9 Ma. The age of Mutigny is important because it is the reference site for the Paleocene–Eocene IV mammalian zone (Hooker, 1996a).

The ages of the three new Montpellierian localities (PLG, CLR/PLD and LLN) make it possible to establish a local correlation to estimate the age of the very spiciose fossiliferous localities of Mas de Gimel/ Naples. The latter belongs to lignite-rich deposits just below the *calcaires lutétiens* (Cappetta et al., 1968; Vianey-Liaud et al., 2024). Such lignite-rich deposits are known in the SDV-A and D sedimentological sections (Fig. 2, middle unit). Considering the large number of common taxa between MGL/NAP and CLR and LLN, it is coherent and robust to propose that this unit can be included within the time interval between C23n.2nH2/O and the beginning of C22r, i.e., in the interval 51.23–50.78 Ma. Therefore, the four Montpellierian localities are all younger than Mutigny and Saint Eulalie (Fig. 11), which is coherent with a biostratigraphical age close to MP10. On the other hand, they are all older than Prémontré (C22r), which also has a fauna related to MP10, but which is usually considered as the youngest Ypresian locality of the Paris Basin, stratigraphically above Grauves (see Dégremont et al., 1985; Cavelier, 1987; Louis, 1996; Duprat, 1997).

In the Paris Basin, Prémontré lies just below a hiatus that precedes the Lutetian deposits (e.g., Aubry, 1985; Lecomte, 1994; Neal, 1996) and should therefore be considered as the last occurrence of an MP10 fauna, given the sample of sites of this study. The minimum age for Grauves is therefore constrained by the maximum age of Prémontré (> 50.4 Ma). The *Sables à Unios et Térédines* were correlated to the upper part of the local W6 dinocyst zone, and even to the top of the W6 (Lecomte, 1994), based on sequential interpretation of Neal

**Fig. 11.** European continental fossiliferous localities calibrated in temporal context (Speijer et al., 2020) and mammalian species extensions for the middle Ypresian to early Lutetian (issued from table in Supp data and including taxa in open nomenclature). For localities: solid line = constrained dating, dashed line = dating estimated by correlations; for taxa distributions: thick line = constrained presence from well-dated locality, thin line = presence for correlated locality, and dotted line = not known at this time in the fossil record, but inferred presence. W = Dinoflagellate cyst zone in Paris Basin (Brinkhuis and Biffi, 1993); D = Dinoflagellate cyst zone Northwestern Europe (Speijer et al., 2020); NP = Calc. nannofossils (Speijer et al., 2020). Abbreviated localities: Aum: Aumelas; Azi: Azillanet; BB: Bracklesham Bay; CLR: Coulondres; DC: Dummer's Copes; CB: Condé-en-Brie; LLN: Le Lien; MGL: Mas de Gimel; NAP: Naples; PC6: Peel Common 6; PLD: Plantade; PLG: Plagnol; Rou: Rouzilhac; Sez: Sézanne-Broyes; Vié: Viélase (the localities described in this study are in red).
<figure><img src="image_32.png" /></figure>
(1996). This local zone may correspond to the D8 dinocyst zone (in Hooker, 1998), but this latter author did not position Grauvues in his chart, and only suggested that it may be stratigraphically higher within D8. Following Neal (1996), Grauvues can be placed at the top of NP12 and at the top of C23n. According to Brinkhuis and Biffi (1993), the top of the W6 corresponds to the top of the P7 planktonic foraminiferal zone and/or the first half of the P8 zone, which is correlated in GTS (Speijer et al., 2020) at the transition between NP12 and NP13 calcareous nanofossil zones, and with C23n.1n plus beginning of C22r. King et al. (2016) proposed that the dinocysts found in the *Sables de Cuise* are D8 or even younger. These three proposed correlations have been the subject of debate and it is clear that the correlation between the "local" dinocyst biozonation and the global one needs to be revisited (see Iakovleva et al., 2021). At present, considering these studies and the strong similarities between the mammalian faunas of CLR, MGL, LLN and Grauvues, we can propose that the latter lies within the interval beginning with the Coulondres maximum and ending just before the Prémontré maximum (top of C23n to base of C22r; 51.2–50.4 Ma).

The maximum age for MP10-related faunas has long been debated, mainly because of uncertainties in the ages of Saint-Agnan (possible MP10) and Sézanne-Broyes and Condé-en Brie (~MP8 + 9). The reference locality of MP8 + 9 (Avenay) was previously proposed between 52.38 and 51.68 Ma on the basis of a bioage calculated from the dental surface of 22 species (Escarguel et al., 1997). This is problematic because this numerical age is close to the age obtained for Plagnol (this study), which is supposed to be within the [MP8 + 9-MP10] interval. Lecomte (1994) proposed the following sequence in the Paris Basin, from the oldest to the youngest site: Mutigny, Avenay, Condé-en-Brie, Saint-Agnan, *Sables à Unios et Térédines* Formation (Grauvues, Monthelon, Cuis, Mancy) and Prémontré. He tentatively correlated Saint-Agnan (*Sables de Cuise* Fm.) with the middle part of the W6 local zone (=D8), close to the boundary between C23r and C23n, which is consistent with the Plagnol dating (middle part of C23r – see above). The localities from the *Sables à Unios et Térédines* Fm. correlate with the upper part of the W6 Zone (Neal, 1996), i.e., in C23n as proposed for Grauvues (Fig. 11). The age of Avenay therefore depends on this correlation, as it appears in an unconformable lens between the *Epernay* Formation (Mutigny estimated here in W4/D7b) and the *Sables à Unios et Térédines* (top W6/D8b; Lecomte, 1994; Neal, 1996). Hooker (1998) suggested that Avenay is at the base of D8, but an older age could be suggested, probably within D7c or D8a zones since there is a large gap between the two formations (see Speijer et al., 2020). Avenay could either be correlated with the local W5 zone (correlated with the top of P6 and the base of P7 zones in Brinkhuis and Biffi, 1993; C24n.1n–C23r in Speijer et al., 2020) or with the base of W6 (middle of P7, D7c to D8a, C23r, base of NP12). Avenay, which is the reference locality for the PEV mammalian biozone (Hooker, 1996a), might therefore be estimated to be somewhere between 53 Ma (base of C24n.1n) and 52.3 Ma (base of NP12). Consequently, Condé-en-Brie and Sézanne-Broyes, usually considered equivalent to MP8 + 9 (e.g., Biochrom'97, 1997), belonging to the *Sable de Cuise* in the northern Paris Basin and stratigraphically younger than Avenay, are proposed as NP12 (D8) but older than Saint-Agnan. Finally, the fossiliferous site of Saint-Agnan lies between Avenay and Grauvues (Louis and Laurain, 1983; Cavelier, 1987; Louis, 1996; Duprat, 1997; Escarguel, 1999) and stratigraphically just above Condé-en-Brie and Sézanne-Broyes. It could therefore be contemporaneous with Plagnol (51.9–52.0 Ma) or younger, but still below Grauvues (Fig. 11).

## 5.2. Revised MP10-related faunal distribution and definition of new mammalian European biozones

Our results, in particular the gap between the current European continental biochronological timescale (Speijer et al., 2020) and the ages discussed above, allow us to question the mammalian biozonation at the Neustrian–Grauvian transition and during the Grauvian ELMA. It appears that the age estimates for the MP10-related faunas in southern France are older than those already proposed for the Paris Basin. Notably, the Grauvian, estimated by Speijer et al. (2020) to span from 50.6 Ma to the Ypresian–Lutetian boundary (48.07 Ma), should be considered older (Fig. 12). Historically, the establishment of biozones from a few reference sites was first proposed by Thaler (1972). Only suggested at this time, the term Grauvian was thereafter used by Savage and Russell (1977) to establish a subdivision of the Rhenanium mammal age (Fahlbusch, 1976). The latter term was quickly abandoned and precise limits of the Grauvian subdivision were never defined, except as the interval between the Neustrian (Fahlbusch, 1976; Hooker, 1998) and the Geiseltalian (Franzen, 2005). Recently, the base of the Grauvian was estimated to be within C22n in Speijer et al. (2020), as a result of the use of erroneous Avenay and Grauvues ages (Escarguel et al., 1997; Hooker, 1998).

The new data obtained from fossil localities in a robust stratigraphical sequence near Montpellier lead to the proposal of a temporal distribution of mammalian taxa (Supp data, Fig. 11). Such a distribution allows the identification of First Occurrence Datum (FOD) and Last Occurrence Datum (LOD) for all taxa of the European late Ypresian (Fig. 12), considering the age uncertainties for some localities, mainly from the Paris Basin. The mammalian distribution highlights five main phases of diversification and extinction between 53.9 to 48 Ma, framing the Grauvian whether we use multiple-occurrence or single-occurrence taxa (Fig. 12). These events are likely to play a role in the boundaries of the biozones. Blurred boundaries were a key argument that led to the abandonment of the Western European mammalian biozone and the creation of the MP Paleogene reference scale (Fahlbusch, 1976; Schmidt-Kittler et al., 1987). For now, it is clear that new, robust, and refined dating can help to establish reliable biozonation. The development of alternative means of correlation between the continental chronostratigraphy and marine chronostratigraphy (e.g., Hyland and Sheldon, 2013; Noiret et al., 2016) led us to propose a biozonation that should be refined in the future and help to break with, or at least complement, the vision of the MP reference scale. The five faunal shifts observed (Fig. 12) permit proposing four mammalian zones for the second half of the Ypresian, which should complete the biozonation proposed by Hooker (1996a, 1998) for the Neustrian. The four zones (Neustrian X, Grauvian 1, Grauvian 2, and a hypothetical new ELMA) are discussed below and defined in Table 5.

The latest reference level for the Neustrian is represented by Avenay (MP8 + 9). Schmidt-Kittler et al. (1987) suggested the possibility of subdividing this reference level in two – with Mutigny or Pourcy as MP8 and Avenay as MP9 – but it has been left as MP8 + 9, for lack of robust data (Biochrom'97, 1997). Hooker (1998) also observed a faunal difference and proposed two zones (PEIV and PEV) but he used the faunas of Condé-en-Brie and Sézanne-Broyes with Avenay to create the PEV. Although most of the differences between the two zones have been explained by metatherian evolution (Schmidt-Kittler et al., 1987: 21), a recent study of one of the two families recorded in Europe (Peradectidae) does not support such a difference, as the same

**Fig. 12.** Synthesis proposing a count of First Occurrence Datum (FOD) and Last Occurrence Datum (LOD) from Figure 11 for multiple occurrence taxa (i.e., known from multiple localities) and from table in Supp data for single occurrence taxa (known from only one locality). The most important faunal turnovers associated with FOD and LOD counts, correlated with δ¹³C and δ¹⁸O curves from CENOGRID (Westerhold et al., 2020), help to propose new biozonation dates and correlations with major climatic events. The dark-coloured arrows represent LOD and FOD of taxa with multiple occurrences, and the light-coloured arrows represent the LOD and FOD of all taxa, including those with a single occurrence.
<figure><img src="image_33.png" /></figure>
<table><caption>**Table 5**
Proposed definition of new Grauvian biozones. Only taxa with multiple occurrences are used here (as in Fig. 11), but singletons are used in addition to calculate taxon richness.</caption><thead><tr><th>Name of biochiron</th><th>Equivalence</th><th>Limit lower/upper</th><th>Localities</th><th>Nb sp/gen</th><th>Taxa restricted to the zone</th><th>First appearance</th><th>Nb/% FOD</th><th>Last appearance</th><th>Nb/% LOD</th></tr></thead><tbody><tr><td>NeX</td><td>MP8 + 9<br>PEIV + PEV</td><td>From the lowermost age proposed for Mutigny to uppermost age proposed for Sézanne-Broyes (~53.9-52 Ma)</td><td>Mutigny, Avenay, Saint-Eulalie, La Borie, Condé-en-Brie, Sézanne-Broyes</td><td>79/55</td><td>Fra. tresvauxi. Sor. tresvauxae, Apa. sigogneaui, Apa. mutignacus, Neo. luciannae, Mac. cf. nitens, Macrocronium sp. (sensu Russell et al., 1975). Pla. Lotus, Leptacodon, Arc. brailloni, Ageina, Ica. menui, Spa. chandoni, Pla. daubrei, Ave. Anatorium, Can. savagei, Unh. hookeri, Que. smithii, Ple. munieri, Ple. lemoinei, Buxolestes, Gilridae, Ailuravus, Ple. savagei, Har. hautefeuilli, Har. marandati, Mas. mattaerteni, Pro. curvicuspids, Nan. zuccolae, Pro. gaudyi, Pac. livinierensis, Hyr. stehlini, Pro. oweni, Ciù. lydekkeri</td><td>Perad. louisi, Perad. russelli, Fra. tresvauxi. Sor. tresvauxae, Apa. sigogneaui, Apa. mutignacus, Neo. luciannae, Mac. cf. nitens, Macrocronium sp. (sensu Russell et al., 1975). Pla. Lotus, Leptacodon, Arc. brailloni, Ageina, Ica. menui, Spa. chandoni, Pla. daubrei, Ave. Anatorium, Can. savagei, Unh. hookeri, Que. smithii, Ple. munieri, Ple. lemoinei, Buxolestes, Gilridae, Ailuravus, Ple. savagei, Har. hautefeuilli, Har. marandati, Mas. mattaerteni, Pro. curvicuspids, Nan. zuccolae, Pro. gaudyi, Pac. livinierensis, Hyr. stehlini, Pro. oweni, Ciù. lydekkeri</td><td>22/27.8 %</td><td>Neoplagiaulacidae, Pse. agiensis</td><td>3/3.8 %</td></tr><tr><td>Gr1</td><td>MP107</td><td>From M hyperthermal (Plagno) to the more recent age estimated for St Agnan, just before Coulondres (~52-51.3 Ma)</td><td>Plagno, Saint-Agnan</td><td>40/37</td><td>None</td><td></td><td>15/37.5 %</td><td>Perad. louisi, Apa. multinacus, Neo. luciannae, Mel. louisi, Pse. theillardi, Pan. russelli, Arc. fuscus, Don. gallica, Mor. velletere</td><td>9/22.5 %</td></tr><tr><td>Gr2</td><td>MP10a</td><td>From O hyperthermal (Coulondres) to Prémortré (~51.2-50.3 Ma)</td><td>Grauves and sables à Unio et Teredines, Coulondres, Le Lien, Mas de Gimel Azillanet, Prémortré Cos. Viélate, Rouzilhac, Aumelas</td><td>82/57</td><td>Peradectes sp. (Marandat, 1986). Perat. monspeliense, Pan. sabatiéri, Par. gumelii, aff. Pontifactor sp. (this paper). Les. gumelii Mas. cosensis, Lop. leptarynchum, Pron. cosensis, Lophiobunodon</td><td>Amp. bastbergense, Heterolykus sp. (this paper), Pal. tupaiodon, Har. pailladensis, Anchomys, Leo. meridianum, Mat. peignei, Pac. ruscassertensis, Lop. cf. leptarynchum</td><td>21/25.6 %</td><td>Ica. menui, Ail. inexpectatus, Eur. woodi, Ple. savagei, Har. hautefeuilli, Har. marandati, Mas. mattaerteni, Arc. Iapparenteni, Pro. curvicuspids, Nan. zuccolae, Cyn. smithae</td><td>22/26.8 %</td></tr><tr><td>New ELMA?</td><td>MP10b</td><td>In the interval between Prémortré and Messel (~50.3-48 Ma)</td><td></td><td>45/34</td><td></td><td>Mac. tupaiodon, Oxy. bicuspids, Lophiotherium, Aum. gabineaudi</td><td>24/53.3 %</td><td>Peratherium matronense, Macrocronium sp. (sensu Russell et al., 1975). Eog. wildi, Ail michaxii, Leo. meridianum, Mat. peignei, Hyr. stehlini, Oro. maldani, Pro. gaudyi, Pac. livinierensis, Pac. ruscassertensis, Eur. russelli</td><td>32/71 %</td></tr></tbody></table>

Peradectes species (*Peradectes louisi* and *Peradectes russelli*) are present in Mutigny and PEV localities (Gernelle et al., 2024a). This, in addition to the synonymy of the earliest species of the two herpetotheriid putative lineages (*sensu Crochet*, 1980) which have been suggested to evolve between Mutigny and younger Paris Basin localities, namely *Amphiperatherium brabantense* and *Peratherium constans* (Ladevèze et al., 2012), attenuates the faunal difference concluded by Schmidt-Kittler et al. (1987, p. 21) and stresses the need for a comprehensive review of Herpetotheriidae. In the same way, recent studies of paromomyids (López-Torres and Silcox, 2018), perissodactyls (Vautrin et al., 2020; Bronnert and Métais, 2023) and rodents (Vianey-Liaud and Marivaux, 2021) also highlight the importance of further systematic revisions of this zonation. Finally, only a few of the differences previously highlighted between Mutigny and Avenay (Fig. 11) remain. In fact, the majority of these differences can be attributed to Avenay and Condé-en-Brie plus Sézanne-Broyes (Fig. 11). This is likely due to the necessity for revision of these two latter faunas, as already proposed by Louis (1996). For the moment, we keep all the MP8 + 9-related faunas in a unique zone, considered as the last Neustrian zone (Table 5). We propose the provisional name of Neustrian X zone (NeX), and a number should be proposed after revision of older Neustrian localities (Fig. 12). This zone begins with Mutigny and may extend until Sézanne-Broyes, which occurs just prior to Plagno!. It is defined by the interval between the first appearance of 21/23 taxa (Table 5) and the last appearance of Neoplagiaulacidae and *Pseudoparamys ageiensis*. There are seven taxa with a distribution restricted to this zone (Table 5). Even if the youngest limit of the zone is well marked by the numerous FOD of the next zone (Fig. 12, Table 5), it is only underlined by two LODs (Table 5). The period spanning from Avenay to Sézanne-Broyes is marked by at least 14/21 LODs (Fig. 12), and therefore the upper limit of this zone should be precisely determined further. Indeed the Sézanne-Broyes fauna includes three taxa emblematic of the Grauvian (*Lophiodon*, *Diacodexis* aff. *varleti* and cf. *Eurodexis russelli*) and presents the noticeable absence of NeX taxa: *Euromys thaleri*, *Sparnacomys chandoni*, *Fratrodon* and *Sororodon*. Despite these uncertainties on the upper limit, we partly disagree with the ages proposed for the PEIV and PEV (Figs. 11, 12). Indeed, they were initially proposed to be both within C23 (Vandenberghe et al., 2012; Speijer et al., 2020). Alternatively, we consider here that they are older, with NeX that should span approximately from the end of C24n.3n (53.4 Ma) with the age of Mutigny here estimated as younger than Fournes dating, to around C23rH2/M (52.0 Ma) with Sézanne-Broyes here estimated just before Plagno! (Fig. 12). Stratigraphical sequences including localities of this age from southern France (e.g., La Borie, MP8 + 9: Laurent et al., 2010) could lead to further precision on the Neustrian zonation. It is unfortunate that a possible intra-European bioprovincialism (North vs. South) has been advocated for this period (Marandat, 1997; Marandat et al., 2012; Solé et al., 2015, 2018), potentially hindering the establishment of correlations with localities from the Paris Basin, although some groups are exceptions to this pattern (e.g., metatherians and paromomyids; López-Torres and Silcox, 2018; Gernelle et al., 2024a).

The transition between the Neustrian and Grauvian stages is characterised by a relatively long phase, identified as a faunal turnover, which could last from approximately 52.4 to 52 Ma, taking into account the uncertainties linked to the estimated age of Condé-en-Brie and Sézanne-Broyes. The initial phase of this evolutionary process was characterised by a high frequency of extinction events and a paucity of observed instances of speciation. This period of transition was followed by a rapid and significant diversification event, which started around 52 Ma near C23r.H2/M. However, the duration of this event is uncertain due to the estimated age of Saint-Agnan. This event coincides with the appearance of important index taxa of the MP10 fauna (Table 5), including six rodent taxa with the earliest Gliridae, the two primates *Protoadapis curvicuspids* and *Nannopithex zuccolae*, and some common ungulates such as the palaeothere *Propalaeotherium gaudryi*,
the earliest European rhinocerotoid *Hyrachyus stehlini* and the two artiodactyls *Protodichobune oweni* and *Cuisitherium lydekkeri* (Fig. 11; Supplementary data). Six of these taxa were previously mentioned as being known only recorded from the reference level of Grauves (*Ailuravus michauxi*, *Plesiarctomys savagei*, *Propalaeoerium gaudryi*, *Hyrachyus stehlini* and *Cuisitherium lydekkeri*) or correlated localities (*Protoadapis curvicuspids*) (Schmidt-Kittler et al., 1987), with some additions (*Nannopithex zuccolae*, *Masillamys mattaueri* and *Protodichobune oweni*) in Biochrom'97 (1997). Considering that the Plagnol locality, which is here positioned in the interval [MP8 + 9–MP10], has *Eogliravus* and *Cuisitherium lydekkeri*, two of the MP10 index taxa, and that it is quite older than Grauves, we propose that Plagnol, at the base of the lower silt-dominated unit of Serre-de-Vias section, can define the early stage of biozone Grauvian 1 (Gr1; Table 5). The aim of this proposal is to set the boundary between the Neustrian and Grauvian zones back by 1.5 million years, and to locate it at the event illustrated by the numerous speciation events at Plagnol/Saint-Agnan. This would result in a Neustrian–Grauvian boundary at 52 Ma. The Gr1 biozone extends until the next faunal turnover, which is recorded between Saint-Agnan and Coulondres (Fig. 12). It is characterised by 16/21 FODs and 9 LODs. This limit notably corresponds to the extinction of typical Neustrian taxa, which are quite abundant in Mutigny, such as *Peradectes louisi*, *Pataemys mutiniacus*, *Neomatronella luciannae*, *Meldimys louisi*, *Pseudoparamys teilhardi*, *Pantrogna russelli*, *Arcius fuscus*, or known since Avenay such as *Donrussellia gallica* and *Morlodon vellerei*.

The numerous first appearances recorded at the maximal age of Coulondres, Mas de Gimel and Grauves (Fig. 12) are characterised by taxa restricted to the new biozone Grauvian 2 (Gr2, Table 5) such as *Pantolestes sabatieri*, *Paraspaniella gunnelli*, and *Lesmesodon gunnelli*, together with three taxa unfortunately only known from southern France, namely aff. *Pontifactor* sp. (this paper), *Peradectes* sp. (sensu Marandat, 1986) and *Peratherium monspeliense*. Nevertheless, less progress has been made so far in reviewing the faunas of the Paris Basin concerning Metatheria and Eulipothyphla. Consequently, the possibility of their presence in Northern France cannot be excluded (e.g., cf. *Pontifactor* from Prémontré, and *Peradectes* aff. *dufraingi* from Grauves documented only by lower molars; Dégremont et al., 1985; Gernelle et al., 2024a). This limit is also the earliest occurrence of *Amphiperatherium bastbergense*. *Palaeochiropteryx tupaiodon* (although this is uncertain for the latter two), and *Anchomomys*, that could be used as index taxa, as well as some southern restricted taxa, namely *Leonhardtina meridianum*, *Matthodon peignei*, and *Pachynolophus ruscasseriensis*. The presence of *Lophiodon* cf. *leptorynchum* in the Paris Basin is currently unknown. A discussion should be opened on the status of *Lophiodon* cf. *leptorynchum* and *Lophiodon remense*. There is no principal faunal turnover in the vicinity of Prémontré. It is evident that numerous extinctions occurred between Grauves and Prémontré. However, it appears that there is a taphonomic bias between the *Sables à Unios et Térédines* and the rich locality of Prémontré, particularly in the absence in the Prémontré locality of several important large mammals, including carnivoramorph (*Intercycon*), *Lophiodon*, and some palaeotheres (*Pro. gaudryi*) and artiodactyls. Despite this problem, we consider the faunal turnover IV (Fig. 12) as the upper limit of biozone Grauvian 2 (Gr2, Table 5), near 50.3 Ma. The main taxonomic extinction at this limit is the last known taxa of the Neustrian like *Icaronycteris menui*, *Euromys woodi*, and *Arcius lapparenti* (with the exception of the questionable *Peratherium matronense*, *Amphiperatherium goethei*, *Macrocranon* sp. [sensu Russell et al., 1975], *Orolophus maldani*), and taxa that appeared first at biozone Gr1 such as *Ailuravus inexpectatus*, *Plesiarctomys savagei*, *Hartenbergeromys hautefeuillei*, *Hartenbergeromys marandati*, *Masillamys mattaueri*, *Protoadapis curvicuspids*, and *Nannopithex zuccolae*. Some of these last occurrences have already been mentioned for MP10 (*Arcius lapparenti*, *Plesiarctomys savagei*; Schmidt-Kittler et al., 1987).

A significant temporal gap exists in the northern basins between the biozone Gr2 and the Lutetian Messel locality, during which no fossiliferous localities have been identified. This study estimated the duration of

this gap in the sedimentation to be approximately two million years, spanning the interval between 50 and 48 million years ago. This hiatus has already been proposed at the end of Ypresian for the Paris, Hampshire–London, and Belgium Basins (e.g., Aubry, 1985; Pomerol, 1989; Payros et al., 2009). Many fossiliferous localities from southern France could fill this interval, but unfortunately their precise datings are still lacking at the moment. The locality of Rouzilhac was proposed as MP10b or the [MP10–MP11] interval (Godinot et al., 2018) and includes many taxa also known from Aumelas (Rémy et al., 2019; Luccisano et al., 2020; Solé et al., 2020). The latter is situated in a quite continuous sequence, and therefore refined dating can be expected in the future. In the meantime, we propose that this interval could represent a new ELMA (Table 5). Indeed, the most emblematic Grauvian taxa have already gone extinct, and we record a new mammalian assemblage, as demonstrated by the numerous new taxon occurrences (8/24). It is possible that this new ELMA will be followed by a major faunal shift as evidenced by the 4/44 FODs and 16/32 LODs recorded near the Ypresian–Lutetian transition.

### 5.3. Impact of the EECO on European mammals

The impact of the EECO on mammal faunas has already been discussed in the context of the North American fossil record at the age scale (Figueirido et al., 2012) or at the biochron scale (Woodburne et al., 2009a). Both studies pointed out the effect of the EECO on diversification (late Wasatchian and early Bridgerian) and on the subsequent cooling on extirpation and decline of generic richness (Bridgerian crash). In Europe, the identification of faunal turnover linked to either dispersal or climatic events has already been suggested (e.g., Solé et al., 2021). However, the imprecision of the datings prevents correct interpretations, particularly in relation to the MP10-related faunas after the EECO, and not within. The five faunal turnovers identified in this study can thus be dated with relatively high precision and, by comparison with the benthic foraminiferal $\delta^{13}$C, be correlated with the benthic foraminiferal $\delta^{18}$O curve (Westerhold et al., 2020), thus enabling the interpretation of the climatic event in question.

The late Neustrian faunal turnover (I), corresponding with the beginning of biozone NeX, is included within the interval between the basis of C24n.2r and the hyperthermal C24n.1nH1/ETM3, i.e., [53.4–52.8 Ma]. Among the few studies, which previously correlated the Neustrian (ELMA) and Wasatchian (NALMA) faunas, Noiret et al. (2016), using marine biostratigraphy and chemostratigraphy, refined the age of the Fournes (Minervois) locality, referred to the [MP7–MP8 + 9] interval, to the middle part of biochron NP11, just above the ETM2, recognised in Wa5 in Wyoming (Abels et al., 2012). This suggests that ETM2 is not a potential base of biozone NeX. The beginning of biozone NeX thus encompasses the EECO onset, despite the lack of clarity surrounding its exact lower limit (C24n2r.H1/J event at 53.26 Ma, as outlined by Westerhold et al., 2018). It is regarded as one of the warmest intervals of the EECO, due to its notable negative mean value of $\delta^{18}$O (Fig. 12; C24n2r.H1/J to C24n.1nH1/K, 53.260–52.845 Ma in Westerhold et al., 2018). This ~500 kya warming period is therefore thought to have led to the diversification of European mammals, with a total richness of 79 species and 55 genera. However, the evidence for this is only present in the Paris Basin. The precise dating of the locality of La Borie and other MP8 + 9-related faunas in southwestern France could assist in the precise impact of this event. Furthermore, an increase in FODs between Wa5 and Wa6 (which occurred contemporaneously with the beginning of biozone NeX) has also been observed in North America (Woodburne et al., 2009a). This indicates that the rate of speciation has increased, with only a few immigrants. The data presented in Woodburne et al. (2009b) indicates nearly equal rate of FODs and LODs in Wa6–Wa7. This contrasts with our observations of biozone NeX, where FODs are largely dominant over LODs (27.8 % vs. 3.8 %). However, the inclusion or exclusion of Condé-en-Brie and Sézanne-Broyes in biozone NeX affects these observations (Fig. 11).
The early Grauvian turnover (II, Fig. 12), including the beginning of biozone Gr1 and here dated by Plagnol (~52 Ma), is characterised by a short period of extinctions, which decreased in number progressively. This phase is interpreted as the interval between the hyperthermals C23rH1/L and C23rH2/M. It corresponds to a positive trend of δ¹³C and δ¹⁸O, of which the latter could be interpreted as a short cooling. The beginning of biozone Gr1 corresponds to a diversification phase and to the onset of the second warmest period of the EECO, as defined by Westerhold et al. (2018; C23rH2/M to C23n.2nH2/O, 51.970–51.230 Ma). Indeed, the whole biozone Gr1 can be defined here by this warm interval. This period also coincides with the appearance of the Asian immigrant rhinocerotoid *Hyrachyus stehlini* and to the increase in body size of Lophiodontidae (>200 kg), specifically in the genus *Lophiodon* (Vautrin, 2019). This is comparable to the observations made at the Wasatchian-Bridgerian boundary (Wa7-Br1a; note that Br0 has been abandoned since Gunnell et al., 2009) in C23r, at approximately 52 Ma (Clyde et al., 2001; Tsukui and Clyde, 2012; Speijer et al., 2020). At this time, the first occurrence of *Hyrachyus* is documented, and the bronthotheres become the largest known herbivores, thus representing a possible ecomorph of European lophiodontids. It can be reasonably deduced that a significant dispersal event occurred in the Northern Hemisphere at this time, with the concomitant arrival of *Hyrachyus* in Europe and North America from Asia (Woodburne et al., 2009b). Furthermore, it is notable that the FOD of the microchoerine omomyiform primate *Nannopithex* in Europe occurred in parallel, with a change in the relative abundances of omomyiform sub-families in North America, between anaptomorphines and omomyines. Similarly, we observed a diversification of artiodactyls, with the emergence of the euartiodactyl molar pattern in *Cuisitherium lydekkeri* and the appearance of bunodont taxa, including *Protodichobune* (Sudre et al., 1983). Additionally, the metaconule enlargement emerged, which contrasts with the triangular occlusal pattern of the upper molars of the Neustrian Diacodexiidae (*Diacodexis* and *Bunophorus*). This phenomenon may also be paralleled with the diversification of Homacodontidae in North America.

The main difference with North America in terms of biozonation is that we have divided the equivalent period of Br1a into two biozones (Gr1 and Gr2) based on some faunal differences, but this may also reflect a paucity of fossiliferous localities for biozone Gr1. It may correspond to the old designation of Br0, which was later abandoned because the differences between Br0 and Br1 were unclear (Gunnell et al., 2009; Woodburne et al., 2009b). For the time being, we have retained the zonation based on the important faunal turnover recorded between Saint-Agnan and Grauves (Gr1 to Gr2; turnover III in Fig. 12). This second Grauvian turnover is dated with the locality of Coulondres/Plantade, and roughly corresponds to C23n.2nH2/O. This important diversification event (16/21 FODs and 9 LODs) coincides with the beginning of the High Amplitude Climate Fluctuation phase of the EECO identified by Westerhold et al. (2018) between 51.5 and 50.5 Ma (Fig. 12). This period surrounds the peak of the EECO (Hyland et al., 2018), with the highest atmospheric CO₂ values in the Cenozoic (The Cenozoic CO Proxy Integration Project (CenCOPIP) Consortium et al., 2023), and has been interpreted as a period of unstable climate conditions (Westerhold et al., 2018), with rapid warming, wet conditions for continental deposits (Hyland and Sheldon, 2013), and extreme summer temperatures in continental interiors (Hyland et al., 2018). In spite of this great climatic fluctuation, the fauna appears quite homogeneous in the southern and northern basins of Western Europe. The end of this climatic phase coincides with the last known site of Prémontré with a Gr2 fauna and another faunal turnover (IV, Fig. 12).

During the Gr2 biozone, we record the highest number of species (82) and genera (57) for the entire late Ypresian to early Lutetian period (Supp data, Table 5). Woodburne et al. (2009a) noted the same pattern for Br1a, with the richest generic fauna (104) compared to other biochrons, and with FADs greatly outnumbering LADs. It should be noted that the two faunal turnovers recorded at the beginning of Gr1 and Gr2 are also characterised by this balance between diversification and extinction, with FODs largely superior to LODs (Fig. 12). During

the Grauvian (Gr1 + Gr2), FODs outnumbered or equaled LODs, whereas this balance reversed in the latest Ypresian, with LODs outnumbering FODs. This pattern is quite similar to that observed in North America, which heralds an equivalent to the Bridgerian Crash (Woodburne et al., 2009a). Unfortunately, the end of the Ypresian in Europe is not as well resolved as the Grauvian, mainly due to the important sedimentological hiatus in the northern basins (e.g., Aubry, 1985; Payros et al., 2009). At present, we do not detect any significant turnover before the Ypresian–Lutetian (turnover V, Fig. 12). Thus, the long period from the site of Prémontré to the site of Messel, to which no ELMA is attributed, corresponds to the end of the EECO and the onset of the subsequent cooling (Fig. 12). It is correlated with the Bridgerian Crash (Br1b, Br2 and beginning of Br3) defined from North America (Woodburne et al., 2009a; Speijer et al., 2020). It corresponds to localities with relatively lower taxon richness (34 genera and 45 species, almost half the richness of biozone Gr2) and an increase in LODs (32, the most important for the second part of the Ypresian). This hypothetical turnover IV seems to be an important period with a complete renewal of the fauna with almost 22 extinctions (+18 extinctions, depending on the eveness of Prémontré) and 24 appearances, thus 53 % of the total species of the period. The turnover IV is also characterised by a continuous increase in the body size of *Lophiodon*, the appearance of the selenodont *Lophiobunodon*, and the radiation of the palaeotheriid perissodactyls and cercamoniine primates.

It is therefore necessary to attempt to recognise the end of the Ypresian in Europe in terms of mammal faunas, as it may represent an important event linked to the post-EECO cooling. This period is particularly well represented in the South of France and efforts must be made in this direction.

## 6. Conclusions

The fossiliferous continental sedimentary succession in the Montpellier area has recorded the magnetic polarity reversals and hyperthermal events characteristic of the late Ypresian. This well-calibrated continental sequence, unique in Europe, allows us to date and revise the temporal distribution of mammals in that continent. Our results strengthen the existence of 1) two major diversification events (turnovers I and II) which are concomitant with the beginning of the two warmest intervals within the EECO, 2) a period of faunal homogeneity and stability in Western Europe with a very rich fauna (57 genera and 82 species), which is coeval with the so-called Ypresian High Amplitude Climate Fluctuations phase, and 3) an hypothetical decrease in diversity that begins with the end of the EECO and the onset of cooling (57 to 34 genera and 82 to 45 species after Gr2). As a result, a direct correlation between faunal diversity and climatic change could be evoked, consistent with that known for the evolution of Ypresian mammalian diversity in North America. We estimate the time of expansion for the MP10-related fauna (52–50.3 Ma) and propose a division of this fauna into three biozones: Gr1 (52–51.2 Ma), Gr2 (51.2–50.3 Ma) and a yet to be named hypothetical final biozone that should correspond to a new ELMA (50.3–48 Ma). Further studies are needed to explore the diversity patterns for the late Neustrian and late Ypresian by achieving a refined integrated chronology of stratified localities. Such localities, under study, have been identified in southern France (La Borie and Saint-Eulalie for the late Neustrian and Aumelas, La Livinière, and Rouzilhac for the late Ypresian's new ELMA). Our study confirms that the combination of dating methods is really a powerful tool and will certainly lead to a revival of European mammalian continental biochronology by revising the MP scale and the ELMA definition. This is a prerequisite for diversity studies in a global climatic context.

### CREDiT authorship contribution statement

**Fabrice Lihoreau:** Writing – review & editing, Writing – original draft, Validation, Supervision, Investigation, Funding acquisition, Formal
analysis, Data curation, Conceptualization. **Johan Yans:** Writing – review & editing, Writing – original draft, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Mouloud Benammi:** Writing – review & editing, Validation, Methodology, Investigation, Formal analysis, Data curation. **Flavia Girard:** Writing – review & editing, Writing – original draft, Validation, Project administration, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. **Gregory Ballas:** Writing – review & editing, Writing – original draft, Validation, Investigation, Formal analysis, Data curation, Conceptualization. **Hélène Bourget:** Writing – review & editing, Validation, Methodology, Investigation, Data curation. **Cindy Boyrie:** Writing – review & editing, Validation, Methodology, Investigation. **Jacinthe Caillaud:** Writing – review & editing, Validation, Methodology, Investigation, Formal analysis. **Floral Solé:** Writing – review & editing, Validation, Investigation, Formal analysis. **Xavier Valentin:** Writing – review & editing, Validation, Methodology, Investigation. **Quentin Vautrin:** Writing – review & editing, Validation, Investigation, Formal analysis. **Monique Vianey-Liaud:** Writing – review & editing, Validation, Investigation, Formal analysis. **Rodolphe Tabuce:** Writing – review & editing, Writing – original draft, Validation, Project administration, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgements

This study is dedicated to our late colleague JY Crochet who initiated roadwork monitoring and research in this area. We are indebted to B. Marandat, S. Jiquel, V. Girard, M. Seranne, and G. Garcia who helped us in the field to collect material and to identify the geology. We would like to thank C. Noiret and our colleague from Namur for the geochemical data. This study benefited from the help of the Palaeontology Master students of the University of Montpellier/Poitiers (promotion 2008, 2018 and 2020) and from the Master preliminary study of C. Guignard. We acknowledged G. Métais and one anonymous reviewer for their careful reading and pertinent comments. We are grateful to the Département de l'Hérault (J.P. Crémieu and T.O Sughrue) for the permission to excavate along the L.I.E.N. (D68). We are grateful to the MRI platform member of the national infrastructure France-Biolmaging supported by the French National Research Agency (ANR-10-INBS-04, "Investments for the future"), and of the Labex CEMEB (ANR-10-LABX-0004) and NUMEV (ANR-10-LABX-0020) for access to the µCT-scanning station EasyTom 150/Rx Solutions (ISE-M, Montpellier, France). This research was financed in part or in full by the ANR, EDENs programme 20-CE02-0007, and by the TelluS Program of CNRS/INSU-2020. A CC-BY public copyright licence has been applied by the authors to the present document and will be applied to all subsequent versions up to the Author Accepted Manuscript arising from this submission, in accordance with the open access conditions of the grant.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.pgeola.2025.01.001.

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