# Evolution of dietary preferences of the Lophiodontidae (Mammalia, Perissodactyla) from Southern France

Manon Hullot, Céline Robinet, Quentin Vautrin, Rodolphe Tabuce, Pierre-Olivier Antoine, Gildas Merceron, Fabrice Lihoreau

► To cite this version:

Manon Hullot, Céline Robinet, Quentin Vautrin, Rodolphe Tabuce, Pierre-Olivier Antoine, et al. Evolution of dietary preferences of the Lophiodontidae (Mammalia, Perissodactyla) from Southern France. Palaeogeography, Palaeoclimatology, Palaeoecology, 2025, 675, pp.113076. 10.1016/j.palaeo.2025.113076. hal-05110000

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1 **Title:** Evolution of dietary preferences of the Lophiodontidae (Mammalia, Perissodactyla) from Southern France

2 France

3

4 **Authors:** Manon Hullot*,a,<fnref n="1" />, Céline Robineta, Quentin Vautrina,<fnref n="2" />, Rodolphe Tabucea, Pierre-Olivier Antoinea, Gildas Merceronb, Fabrice Lihoreaua

5 Antoinea, Gildas Merceronb, Fabrice Lihoreaua

6

7 Affiliations

8 a- Institut des Sciences de l'Evolution de Montpellier, UMR5554, CNRS, Univ Montpellier, IRD

9 Place Eugène Bataillon, CC064, 34095 Montpellier, France

10 b- Laboratoire PALEVOPRIM, UMR7262, CNRS and Université de Poitiers

11 Bat. B35, TSA-51106, 86073 Poitiers France

12

13 * Corresponding author: manon.hullot@gmail.com

14

15

<footnote n="1">¹ present affiliation and address: JURASSICA Museum, Route de Fontenais 21, 2900 Porrentruy, Switzerland / Université de Fribourg, Department of Geosciences, Chemin du musée 4, 1700 Fribourg, Switzerland</footnote>

<footnote n="2">² present affiliation and permanent address: Réserve Naturelle Nationale d'Intérêt Géologique du département du Lot, Parc Naturel Régional des Causses du Quercy-Géoparc Mondial UNESCO des Causses du Quercy, Les Canavals, BP 10, Labastide Murat 46240 Cœur-de-Causse, France</footnote>
16 Abstract

17

18 During the Eocene, the Lophiodontidae experienced an increase in body mass and a tendency towards
19 the molarisation of the premolars, two phenomena often related with dietary changes. Although being
20 amongst the largest herbivores of the European landmass at that time, the ecology of this successful
21 perissodactyl family has rarely been investigated. This work is the first to take interest in the temporal
22 evolution of dietary preferences of lophiodontids using enamel microstructure, dental mesowear and
23 microwear (DMTA), in relation to body mass. We studied the Lophiodontidae (188 specimens) from
24 seven Southern France localities dated from the early Ypresian (Mammal Palaeogene levels ]MP7-8+9[
25 interval, Palette), middle Ypresian (~MP8+9, La Borie, Sainte-Eulalie), late Ypresian (~MP10 Naples 2;
26 ]MP10-11[ interval, Aumelas), Lutetian (?MP11-12, Saint-Martin-de-Londres) and late Bartonian (MP16,
27 Robiac; Last Appearance Datum of the family). Regarding enamel microstructure only *Lophiaspis*
28 *maurettei* from Palette can be discriminated by its *Schmelzmuster*, with a large proportion of inner radial
29 enamel, low decussation and straight Hunter-Schreger bands. The mesowear of the three oldest and
30 smallest lophiodontids (85-350 kg) suggests similar browsing preferences, while the DMTA and
31 microstructure exclude the consumption of abrasive and hard items. All proxies indicate tough foliage
32 browsing, contrasting with the traditional view of all stem perissodactyls being frugivorous. Our results
33 suggest that the younger and giant-sized *Lophiodon lautricense* (~ 2300 kg) consumed more abrasive
34 and harder items. Relative reduction of enamel thickness and increase in molarisation appears as a
35 tentative dietary adaptation prior to the family extinction in relation with the MECO event.

36

37 **Keywords:** Eocene, Perissodactyla, body mass, enamel microstructure, mesowear, microwear (DMTA)
1. Introduction

39

The lophiodons were conspicuous elements of endemic European hoofed-mammal faunas during the Eocene. The first Lophiodontidae appeared during the Early Eocene in southwestern Europe and are assigned to *Lophiaspis* and *Eolophiodon* (Depéret, 1910; Robinet et al., 2015; Vautrin et al., 2021). The family rapidly diversified with the radiation of *Lophiodon* and dispersed throughout Western Europe (Holbrook, 2009; Robinet et al., 2015; Vautrin, 2019). In parallel to this radiation, the lophiodontids have experienced a strong increase in size throughout their evolutionary history (Cope-Depéret rule; Cope, 1885; Depéret, 1907), ranging from dog- to pig-sized for the earliest and basal-most lophiodontids (*Lophiaspis* and *Eolophiodon*) to rhinoceros-sized for the latest and more derived species of *Lophiodon* (Vautrin et al., 2019). The size increase of the lophiodontids was synchronous with that of the Brontotheriidae in North America (Lihoreau et al., 2025; Sanisidro et al., 2023), and occurred during the Early Eocene Climatic Optimum (EECO; ~ 53-49 Ma: Westerhold et al., 2020). The Lophiodontidae were the largest herbivorous terrestrial vertebrates within their geographical range, only challenged by the giant flightless - and allegedly herbivore - bird *Gastornis* in Western Europe until its extinction during the Lutetian (MP13; Buffetaut and Angst, 2014). This position as the largest herbivores of the continent, make lophiodontids key parts in structuring European terrestrial ecosystems of the early-middle Eocene interval, similarly to what is observed for today's large mammals (Kohi et al., 2011; Makhabu et al., 2006; Owen-Smith, 1988).

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The evolutionary history of the Lophiodontidae was also marked by a tendency towards the molarisation of the premolars through a gradual bucco-lingual widening of the premolars and the progressive addition of a cusp. Indeed, the first members of the taxa display non-molarised premolars (triangular in occlusal view), while the most recent *Lophiodon* species present partially-molarised premolars (quadrangular in occlusal view, hypocone on upper premolars; Sudre, 1971). Such modifications of the body mass and of the dental morphology could have resulted in modifications of the diet throughout the evolutionary history of the family. However, the diet of early lophiodontids remains unknown. The diet of the first perissodactyls, which present brachydont and buno-lophodont teeth is reconstructed as mainly frugivore (Blondel, 2001; Wilde and Hellmund, 2010). A more folivore diet is thought to have appeared only later within the different perissodactyl families, favoured by an increased
lophodonty (Blondel, 2001). A similar evolutionary trend of the dentition towards molarisation, coupled
with an increased lophodonty or bunoselenodonty, is also observed in multiple other European mammal
taxa during the Eocene (Blondel, 2001; Butler, 1952; Holbrook, 2015). These changes are interpreted
as the result of the opening of the environments and a facilitated access to more fibrous vegetation
(Blondel, 2001; Franzen, 2003). Such evolution in environments might have impacted the ecology of the
lophiodontids and favoured plants eaten with more molarised dentition and higher body mass.

74

However, despite their abundance, their key role in ecosystems, and the morphological changes
in their evolutionary history, few studies focused on lophiodontids' ecology and even less on their diet
(e.g., Koenigswald, 2014). Most works mentioning the ecology of lophiodontids based their
reconstructions on tapirs, as this group has often been considered close phylogenetically and
ecologically due to their general size and bilophodonty (Holbrook, 2009; McKenna and Bell, 1997;
Radinsky, 1963). This notably resulted in misleading and unfounded depictions of lophiodons with a
trunk, and/or with semi-aquatic habits (Maack, 1856). However, while Lophiodontidae have been
historically grouped with tapirs within the Ceratomorpha (Holbrook, 2009; Radinsky, 1969), recent
studies bring lophiodontids closer to chalicotheres within the sub-order Ancylopoda (Bai et al., 2018a;
Hooker and Dashzeveg, 2003; Vautrin et al., 2021). In order to provide an independent insight of their
ecology, we assessed dietary preferences at different time scales: a macro-evolutive scale over several
species of a same lineage with enamel microstructure (Alloing-Séguier et al., 2014; Koenigswald and
Sander, 1997; Tabuce et al., 2017), long term with dental mesowear (Ackermans et al., 2020; Fortelius
and Solounias, 2000; Uzunidis et al., 2024; Uzunidis and Rivals, 2023), and short-term for dental
microwear (Calandra et al., 2016; Hoffman et al., 2015; Teaford et al., 2021; Winkler et al., 2020).
Enamel microstructure is the study of enamel prisms and their organization, which gives insight into the
biomechanical constraints to which the teeth are adapted (Koenigswald et al., 1987). Dental wear results
from the loss of small enamel fragments due to attrition (i.e., tooth-tooth contact) and abrasion (i.e.,
food-tooth contact; Kaiser et al. 2013) and reflects the diet composition, especially in term of physical
properties (Hedberg and DeSantis, 2016; Merceron et al., 2016).

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In this paper we focused on the lophiodontids from seven localities covering the total
stratigraphical range of their evolutionary history to study the possible changes in diet throughout the

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98 Eocene: the basalmost representative *Lophiaspis*, series of two distinct taxa assigned to the early-
99 diverging *Eolophiodon* displaying medium size and non-molarised dentition, and three species of
100 *Lophiodon*, of which *L. lautricense*, a giant form with partly-molarised dentition and the last
101 representative of the family. Using dental proxies and a referential of extant kin (tapirs and rhinoceroses)
102 we propose ecological inferences for these species in the light of body mass, and coeval climatic and
103 environmental changes.
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## 2. Geological settings
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106

107 The fossils of *Lophiaspis maurettei* come from the locality of Palette in the townships of Meyreuil
108 (Aix-en-Provence basin, Southern France; Figure 1). The fossils are found in an argillaceous lens
109 interbedded between lacustrine marls and interpreted as continental fluviatile deposit. Available
110 chemostratigraphic data suggests that the locality is framed by two negative δ¹³C excursions, which
111 possibly correspond to the Palaeocene Eocene Thermal Maximum (PETM: ~ 56 Ma) and the Eocene
112 Thermal Maximum 2 (ETM2: ~ 54 Ma; Cojan et al., 2000). It could be contemporaneous with the
113 localities of Le Clot and Fordones (Southern France; Marandat et al., 2012; Yans et al., 2014) and thus
114 dated between the MP7 from Dormaal (Belgium) and the MP8+9 (Avenay, Paris Basin), in the early
115 Ypresian.
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117 The fossils of *Eolophiodon laboriense* come from the quarry of La Borie, in the township of Saint-
118 Papoul in Lauragais area, Southern France (see Figure 1). The locality is located at the base of the
119 « Argiles rutilantes d'Issel et de Saint-Papoul » Formation. The fossiliferous levels are composed of
120 several layers of lignitous clays intercalated between thick sandstone lenses (Laurent et al., 2010). The
121 top of the formation consists of a conglomeratic sandstone and arkosic sand (Godinot et al., 2018). The
122 locality of La Borie has yielded a rich vertebrate fauna whose age was tentatively correlated with the
123 reference fauna of MP8+9 in the Paris Basin (Bourdon et al., 2014; Laurent et al., 2010; Robinet et al.,
124 2015; Solé et al., 2018). The fauna and flora of La Borie indicate a wooded savannah environment on a
125 flood/alluvial plain, under a humid tropical climate with a light dry season (Laurent et al., 2010).
126

126
<figure><img src="image_2.png" /><figcaption>Figure 1: Location and biostratigraphy of the seven Southern French localities studied.</figcaption></figure>

The location of the localities is indicated on the Eocene palaeomap of Europe (upper; modified from Vicián and Kovács, 2021) and on the current French map configuration (lower). 1 – Palette (MP7-8+9 [interval]), 2 – La Borie, Saint-Papoul (~MP8+9), 3 – Sainte-Eulalie (~MP8+9), 4 – Naples 2 (~MP10), 5 – Aumelas (MP10-11 [interval]), 6 – Saint-Martin-de-Londres (?MP11-12), 7 – Robiac (MP16 reference locality). Biostratigraphy according to past works (Crochet et al., 1988; Danilo et al., 2013; Laurent et al., 2010; Lihoreau et al., 2025; Noiret et al., 2016; Rémy, 2015; Solé et al., 2020, 2018; Vianey-Liaud et al., 2024).

The locality of Sainte-Eulalie, where some specimens firstly assigned to *Lophiopsis* sp. (Danilo et al., 2013) but most probably belonging to *Eolophiodon* (Vautrin, 2019) have been found, is located in the township of La Livinière in Minervois area, Southern France. The locality is close to the top of the
"Grès d'Assignan" Formation (Danilo et al., 2013; Noiret et al., 2016), above the Ventenac limestones dated from the ]MP7-MP8+9[ interval (Noiret et al., 2016) possibly between the hyperthermal events J and L (53.2-52.5 Ma; i.e., 'ETM3 interval' in Noiret et al., 2016; NeX in Lihoreau et al., 2025) and topped by the "Calcaires d'Agel" Formation dated from ~MP10 (Marandat, 1986). Sainte-Eulalie deposits are characterized by a succession of sandstone banks with oncolites and stromatolites and clay deposits and is interpreted as a floodplain or lake shore environment (Danilo et al., 2013).

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The Naples 2 specimens referred to as *Lophiodon cf. leptonchum* were found north to the city of Montpellier (Southern France) very close to the co-eval late Ypresian (~MP10) locality of Mas de Gimel (Vianey-Liaud et al., 2024). Naples 2, which is now covered by the Pierre-de-Coubertin sports hall, is located to the south of the Montpellier thrust and consists of brecciated levels underlain by fossiliferous whitish marly limestone. Naples 2 has mainly yielded well-preserved remains of large mammals, unlike Naples and Mas de Gimel, that have yielded mainly micromammals. The attribution to *Lophiodon cf. leptonchum* awaits a systematic review as it appears to be slightly smaller than *L. leptonchum* and could be synonymous with *L. remense* (Lihoreau et al., 2025; Vianey-Liaud et al., 2024). This fossil assemblage yields among the earliest occurrences of *Lophiodon*, dated by regional lithological correlation to the upper magnetochron C23n, between the hyperthermals O and P (51.2-50.7 Ma; Gr2: Lihoreau et al., 2025).

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The *Lophiodon leptonchum* specimens studied here have been found at the locality of Aumelas, about 30 km west of Montpellier in Southern France. The remains have been first interpreted as *Lophiodon isselense* (Hartenberger, 1963), as *Lophiodon leptonchum* (Hartenberger et al., 1969) and then, more cautiously and due to the high morphological variability found in *Lophiodon* (Sudre, 1971), as "*Lophiodon* sp. indet. (forme de petite taille)" (Sudre, 1980). It has recently been re-interpreted as *L. leptonchum* based on new material (Vautrin, 2019). The fossiliferous deposit of Aumelas is located at the top of a lacustrine limestone series (Rémy et al. 2019). The mammalian fossils come from a shallow layer of sandy limestone, which is deeply indented, dark brown in colour and framed by banks of whitish limestone (Sudre, 1980). The deposit was initially correlated with the "obere Mittelkhole" (MP13) of the Geiseltal (Crochet et al., 1988; Sudre, 1980), but recent revisions of the fauna suggest

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169 an older age within Ypresian (Luccisano et al., 2020; Rémy et al., 2019; Solé et al., 2020) in the interval
170 between Prémontré (50.3 Ma) and Messel (48 Ma; i.e., ]MP10-11[ interval, see Lihoreau et al., 2025).

171
172 The specimens of *Lophiodon tapirotherium* are from Saint-Martin-de-Londres, 15 km north of
173 Montpellier, Southern France. The fossiliferous bed corresponds to marls rich in organic matter within a
174 series of massive limestone, sometimes correlated to the regional "Lutetian limestone" (Crochet et al.,
175 1997, but see Lihoreau et al., 2025). The locality was proposed to be younger than Aumelas (Luccisano
176 et al., 2020; Rémy et al., 2019; Solé et al., 2020) or even younger than Messel, thus MP11 to MP12
177 (Crochet et al., 1988).

178
179 The remains of *Lophiodon lautricense* studied here come from the locality of Robiac, which is
180 the latest attested occurrence of the family (Sudre, 1971). Robiac is located west of the township of
181 Saint-Mamert-du-Gard, at about 20 km north west of Nîmes in Southern France (see Figure 1). The
182 locality consists of two fossiliferous *loci* separated by 500 m – Robiac North and Robiac South – but
183 with homogeneous faunas (Depéret and Carrière, 1901; Rémy, 2015). The *loci* that yielded the remains
184 of Lophiodon lautricense studied were chosen as the reference level MP16 in the biochronological scale
185 of fossil mammals of the Western European Palaeogene (Schmidt-Kittler et al., 1987), and the Robiacian
186 age deposit in the European Land Mammal Ages (ELMA; Savage and Russell, 1983) and European
187 Land Mammal Mega Zone (ELMMZ; Steininger, 1999; Franzen, 2005). Faunal and flora data indicate a
188 tropical, closed and humid forest environment (Legendre, 1989; Rémy, 2015).

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190 3. Materials & Methods

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192 3.1. Materials

193 The fossil dataset of lophiodontids is composed of about 200 specimens, separated by taxa and
194 localities as detailed in Table 1. The lophiodontids specimens used in this study are housed in the
195 collections of the Université de Montpellier (UM), the Muséum d'Histoire Naturelle de Toulouse (MHNT),
196 the Université d'Aix-Marseille (AMU), the Université Lyon 1 – Claude Bernard (FSL) and of the Muséum
197 d'Histoire Naturelle d'Aix-en-Provence (MHN.AIX; list and details on all specimens in Supplementary 1).
198 Due to technical constraints, not all methods could be applied to all samples. Notably, the microstructure
(destructive analysis) could not be studied at Sainte-Eulalie and Naples 2 due to the limited material available and a pending systematic revision, while moulding for microwear analyses has not been allowed at Palette at the time of the study (Table 1).

<caption>**Table 1: Detailed list of the lophiodontid specimens studied.**</caption>

For body mass, several teeth from the same specimen were used (m1-m2). Abbreviations: Gr2 – Grauvian 2 biozone, L. – *Lophiodon*, Ls. – *Lophiaspis*, N – number of teeth, NeX – Neustrian X zone

<table><thead><tr><th>Locality</th><th>Age</th><th>Species</th><th>N micro-structure</th><th>N mesowear</th><th>N microwear</th><th>N body mass</th></tr></thead><tbody><tr><td>Robiac</td><td>MP16</td><td>L. lautricense</td><td>11</td><td>12</td><td>8</td><td>195</td></tr><tr><td>Saint-Martin-de-Londres</td><td>?MP11-12</td><td>L. tapirotherium</td><td>1</td><td>8</td><td>4</td><td>5</td></tr><tr><td>Aumelas</td><td>]MP10-11[ interval, (50-48 Ma)</td><td>L. lektorhynchum</td><td>2</td><td>15</td><td>6</td><td>31</td></tr><tr><td>Naples 2</td><td>~MP10, Gr2 (51.2-50.7 Ma)</td><td>L. cf. lektorhynchum</td><td>-</td><td>6</td><td>12</td><td>21</td></tr><tr><td>Sainte-Eulalie</td><td>~MP8+9, NeX (53.2-52.5 Ma)</td><td>Eolophiodon sp.</td><td>-</td><td>4</td><td>4</td><td>19</td></tr><tr><td>La Borie</td><td>~MP8+9</td><td>E. laboriense</td><td>1</td><td>14</td><td>10</td><td>59</td></tr><tr><td> Palette</td><td>]MP7-8+9[ interval</td><td>Ls. maurettei</td><td>1</td><td>5</td><td>-</td><td>4</td></tr></tbody></table>

## 3.2. Body mass estimations

The body masses of all lophiodontid taxa studied were estimated from linear regression equations based on molar size, and developed by Legendre (1989), Damuth (1990), and Janis (1990). These estimates were made from the abundant dental material available and are summarized in Table 2. Molar size (length and width) was measured with a calliper where the dimensions of the tooth were maximal. To limit the effect of wear, we discarded molars that were very worn from our analyses. For each *locus*, we reported the mean value of the body mass estimate based on all studied specimens by species. We also calculated the mean and standard deviation of all proxies by species.

<caption>**Table 2: Linear regression equations used in the estimation of body mass.**</caption>

In the equations m designates the body mass in kilograms except for Legendre (1989), in which body mass is in grams.

<table><thead><tr><th>References</th><th>Locus</th><th>Equation</th></tr></thead><tbody><tr><td>Legendre (1989)</td><td>m1</td><td>ln(mass) = 1.5133 x ln(m1 length x m1 width) + 3.6515</td></tr><tr><td>Janis (1990)</td><td>m1</td><td>log(mass) = 3.26 x log(m1 length) + 1.337</td></tr></tbody></table>
$$m2 \quad \log(\text{mass}) = 3.2 \times \log(\text{m2 length}) + 1.13$$

$$M2 \quad \log(\text{mass}) = 3.18 \times \log(\text{M2 length}) + 1.091$$

Damuth (1990)

$$m2 \quad \log(\text{mass}) = 3.07 \times \log(\text{m2 length}) + 1.07$$

$$M2 \quad \log(\text{mass}) = 3.03 \times \log(\text{M2 length}) + 1.06$$

### 3.3. Enamel microstructure

The sampled teeth were sectioned in vertical planes on the cusps labio-lingually or mesio-distally. The preparation of the samples was conducted in accordance with the protocols established by Tabuce et al. (2007) and Alloing-Séguier et al. (2014). The specimens were embedded in polyester resin, sectioned, ground and polished. Subsequently, the samples were subjected to 37% phosphoric acid etching for a duration of between 30 and 60 seconds, contingent on the degree of fossilisation, and rinsed with distilled water. Then, the samples were air-dried and coated with a conductive material (platinum) prior to observation with a scanning electron microscope (SEM). In order to conduct this analysis, we employed a SEM at the *Institut des Membranes de Montpellier* (HITACHI S 4800) with magnification from x30 to x1000. From the high-definition pictures, we evaluated a number of parameters in order to describe the microstructure of enamel, following the descriptions and terminology set out by Koenigswald and Sander (1997) and Alloing-Séguier et al. (2014).

### 3.4. Mesowear analyses

We investigated the diet of our lophiodontid samples on a long-term scale using mesowear. Mesowear is traditionally based on occlusal relief and cusp shape of ungulate molars to categorize dietary preferences (Ackermans et al., 2020; Fortelius and Solounias, 2000). With this method, grazers are characterized by low reliefs and blunt cusps suggesting abrasion dominance, whether browsers display higher reliefs and sharper cusps due to attrition dominance. Here, we used the traditional method described by Fortelius & Solounias (2000), but scored only the paracone rather than the sharpest cusp, due to significant differences reported in perissodactyls (Taylor et al., 2013; Hullot et al., 2021). In addition, we used the mesowear ruler by Mihlbachler et al. (2011), as it was designed on horses, that are among living relatives of lophiodontids. With this approach, mesowear scores range from 0 to 6, with browsers having low scores, grazer high scores, and mixed-feeders intermediate ones. We did not
use the hypsodonty index, as our sample is restricted phylogenetically and most lophiodontid species have similar indexes. However, we took into account the effect of age on mesowear (Fortelius and Solounias, 2000) and discarded specimen with too few (young) or too much (old) wear to ensure comparability.

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## 3.5. Dental microwear texture analysis

To assess the diet of lophiodontids on a short-term scale, we studied the shearing facet on the lingual part of the protocone on upper molars and distally to the protoconid or hypoconid (if the protoconid facet was unavailable) on lower molars (Figure 2; Ramdarshan et al., 2017). In order to interpret the microwear data of the lophiodontids, we compared it to the DMTA obtained on homologous facets in several extant relatives with known feeding habits: the five extant species of rhinoceros (Figure 2B) and the Brazilian tapir *Tapirus terrestris* (Figure 2C). We chose rhinoceroses and tapirs, as i) extant Ceratomorpha (tapirs and rhinoceros) provide the closest extant analogs for lophiodontids (Ancylopoda are all extinct), ii) a database for microwear coupled with dietary preferences was already available for rhinoceroses (Hullot et al., 2019) and iii) these extant species cover a wide range of herbivore diets. Indeed, two species of modern rhinos are grazers – the *Ceratotherium simum* (white rhinoceros; obligate grazer: Groves, 1972) and *Rhinoceros unicornis* (Indian rhinoceros; variable grazer with a seasonal shift: Laurie et al., 1983) – while the three others are browsers – *Diceros bicornis* (black rhinoceros; Hillman-Smith and Groves, 1994) and *Rhinoceros sondaicus* (Javan rhinoceros; Groves and Leslie, 2011) are generalists, and *Dicerorhinus sumatrensis* (Sumatran rhinoceros; Groves and Kurt, 1972; Hullot et al., 2019) is folivore. Finally, *Tapirus terrestris* is a tropical forest dweller known to browse mainly on leaves and stems but also prone to consume fruits (capsules and dry fruits with seeds), shoots, aquatic plants, and even grass-like plants (Padilla and Dowler, 1994; Talamoni and Assis, 2009).

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The extant dataset is composed of rhinoceroses (modified from Hullot et al. 2019; shearing facet only) and tapirs distributed as follows: 14 specimens of *Ceratotherium simum* (white rhinoceros), three of *Dicerorhinus sumatrensis* (Sumatran rhinoceros), 16 of *Diceros bicornis* (black rhinoceros), 14 of *Rhinoceros sondaicus* (Javan rhinoceros), four of *Rhinoceros unicornis* (Indian rhinoceros), and 15 of *Tapirus terrestris* (Brazilian tapir). The specimens are curated in different museums and institutions: Université de Montpellier, France (UM), Musée des Confluences in Lyon, France (MHNL), Muséum
275 *National d'Histoire Naturelle* in Paris, France (MNHN), *Musée Royal d'Afrique Centrale* in Tervuren, Belgium (MRAC), University Museum of Zoology of Cambridge, United Kingdom (UMZC), *Naturhistoriches Museum* of Basel, Switzerland (NHMB), *Naturhistorisches Museum* of Vienna, Austria (NHMW) for rhinoceros, and MNHN and *Museo de La Plata, Argentina (MLP) for tapirs.

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

280

<caption>281 **Figure 2: Location of the studied wear facets on upper and lower right molars of the**
282 perissodactyl taxa considered here.</caption>

283 The blue zone represents the location of the shearing wear facet studied here on the teeth of A-
284 lophiodons, B- rhinoceros, C- tapirs. Upper molars are at the top and lower molars at the bottom. Not to
285 scale. Modified from Butler (1952) and Vautrin et al. (2019).

286

287 We followed the casting protocol developed in previous studies (Scott et al., 2006, 2005) and
288 detailed in Hullot et al. (2019), as well as in a Zenodo video (Berlioz et al., 2021). Specimens were first
289 checked for macroscopic taphonomical alterations resulting in the exclusion of several specimens. For
290 the rest, the wear facet of interest was cleaned twice with cotton swab soaked in acetone or ethanol and
291 then moulded twice using polyvinylsiloxane (Regular Body President, ref. 6015 - ISO 4823, medium
292 consistency, polyvinylsiloxane addition type; Coltene Whaledent). The second mould was then used for
293 the microwear analyses using the Leica DCM8 confocal profilometer "TRIDENT" profilometer housed at
294 the Paleovoprim lab (CNRS and University of Poitiers). The scans were obtained with white light confocal
295 technology using the 100× objective (Numerical aperture: 0.90; working distance: 0.9 mm; Leica
296 Microsystems). Then, the scans were checked for microscopic taphonomical alterations, resulting in the
297 exclusion of 22 specimens. The remaining scans were pre-treated under Leica Map v. 8.2 (Leica
298 Microsystems) following different steps: the surface was inverted (as scans were produced on negative
299 replicas), missing (i.e., non-measured) points were replaced by the mean of the neighbouring points,
300 aberrant peaks were removed (see Merceron et al. 2016 for details), surface was levelled and form
301 removal (polynomial of degree 8) was applied. We selected a 200×200-µm area to be used for DMTA
302 Scale-Sensitive Fractal Analysis and ISO parameters with Leica Map. The parameters studied here are:

303 • anisotropy, which measures the orientation concentration of surface roughness. Several
304 parameters can indicate the anisotropy of the surface:

305 (i) epLsar (exact proportion of length-scale anisotropy of relief) or NewepLsar. The latter is the
306 corrected value of epLsar in MountainsMaps® (see details in Calandra et al., 2022);

307 (ii) Str is a spatial parameter of the international standard ISO 25178 (specification and
308 measurement of three-dimensional surface textures). It is the ratio of Rmin/Rmax, where Rmin
309 and Rmax are, respectively, the minor and major axes of the intersection ellipse between the
310 plane z = s with the autocorrelation function fACF(tx, ty). Rmin is the autocorrelation length, i.e.
311 the horizontal distance of the fACF(tx, ty), which decays fastest to a specified value s between
312 0 and 1. Here, following recommendations made by Francisco et al. (2018a, 2018b), we
313 considered s = 0.5. Low values of Str indicate strong anisotropy (Francisco et al., 2018a);

314 • complexity (area-scale fractal complexity; Asfc), which estimates the roughness at a given
315 scale;

316 • heterogeneity of complexity (heterogeneity of area-scale fractal complexity; HAsfc), reflecting
317 the variation of complexity within the studied zone (see Scott et al. 2006 for details).

319 **3.6. Statistics and illustrations**

320 We conducted all the statistical analyses on R (R Core Team 2024: https://www.R-project.org/).

321 Descriptive statistics were obtained with the function "describeBy" from the package psych (Revelle and
322 Revelle, 2015). We used the MVN package (Korkmaz et al., 2014) for multivariate normality and
323 MANOVA. When a Box-Cox transformation for multivariate normality was needed (i.e., data not multi-
324 variate normal), we used that from the car package (Fox et al., 2012) before conducting a MANOVA on
325 microwear parameters (Asfc, HAsfc9, HAsfc81, and Str) to test for species or genus differences for
fossils only, and for fossil and modern species. To precise MANOVA's results, we conducted ANOVAs by species for each parameter and run post-hoc tests (conservative Tukey's HSD and less conservative Fisher's LSD) that determine significant differences between group means in ANOVAs, when necessary. The LSD post-hoc is from the agricolae package (Mendiburu, 2010). All the graphs presented in this study were done using the following R packages, ggplot2 (Wickham, 2011), ggpubr (Kassambara, 2018) and RColorBrewer (Neuwirth and Neuwirth, 2014), as well as Inkscape (v0.91), and Gimp (2.8).

# 4. Results

## 4.1. Body mass

We estimated the body mass of the different lophiodontids at each locality based on molar measurements and various linear regression equations (Damuth, 1990; Janis, 1990; Legendre, 1989). The results are detailed in Table 3, along with the ranges of body mass observed in extant species of rhinoceros and Brazilian tapir for comparison.

<caption>**Table 3: Body mass estimates (in kg) of the lophiodontids included in the study.**</caption>

Estimates of body mass for extinct species were based on molar size. The mean of all studied specimens is given by proxy, and at each locality a general mean and standard deviation (SD) of all proxies is also provided. Abbreviations: *L.* – *Lophiodon*, *Ls.* – *Lophiaspis*. Extant species body mass ranges were found on the website of the International Rhino Foundation (https://rhinos.org/) and the following references (Groves, 1972; Groves and Kurt, 1972; Groves and Leslie, 2011; Hillman-Smith and Groves, 1994; Laurie et al., 1983; Padilla and Dowler, 1994).

<table><thead><tr><th></th><th>m1<br>(Legendre,<br>1989)</th><th>m1<br>(Janis,<br>1990)</th><th>m2<br>(Janis,<br>1990)</th><th>m2<br>(Damuth,<br>1990)</th><th>M2<br>(Janis,<br>1990)</th><th>M2<br>(Damuth,<br>1990)</th><th>Mean<br>(kg)</th><th>SD</th></tr></thead><tbody><tr><td><strong>Fossil</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><em>L. lautricense</em> (Robiac)</td><td>1819.8</td><td>1921</td><td>2854.5</td><td>2000.1</td><td>3319.6</td><td>2000.1</td><td>2319.2</td><td>± 616.3</td></tr><tr><td><em>L. tapirotherium</em> (Saint-Martin-de-Londres)</td><td>403.2</td><td>465.4</td><td>-</td><td>-</td><td>599.9</td><td>465</td><td>483.4</td><td>± 83</td></tr><tr><td><em>L. leptorhynchum</em> (Aumelas)</td><td>281</td><td>318</td><td>321.5</td><td>245.9</td><td>444.4</td><td>349.1</td><td>326.7</td><td>± 67.9</td></tr><tr><td><em>L. cf leptorhynchum</em> (Naples 2)</td><td>208.4</td><td>233</td><td>220.9</td><td>171.6</td><td>269.6</td><td>217</td><td>220.1</td><td>± 32</td></tr><tr><td><em>Eolophiodon</em> sp. (Sainte-Eulalie)</td><td>70.9</td><td>77</td><td>90</td><td>72.5</td><td>109.6</td><td>92</td><td>85.3</td><td>± 14.8</td></tr><tr><td><em>E. laboriense</em> (La Borie)</td><td>99.3</td><td>107.7</td><td>128.4</td><td>101.9</td><td>157.5</td><td>129.9</td><td>120.8</td><td>± 22.3</td></tr><tr><td><em>Ls. maurettei</em> (Palette)</td><td>37.8</td><td>39.4</td><td>43.3</td><td>36</td><td>47.7</td><td>41.7</td><td>41</td><td>± 4.2</td></tr></tbody></table>
<table><thead><tr><th>Extant</th><th></th><th></th><th></th><th></th><th></th><th>Min-Max (kg)</th></tr></thead><tbody><tr><td>Tapirus terrestris</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>150-300</td></tr><tr><td>Ceratotherium simum</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>1600-3600</td></tr><tr><td>Diceros bicornis</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>700-1500</td></tr><tr><td>Dicerorhinus sumatrensis</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>600-950</td></tr><tr><td>Rhinoceros sondaicus</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>900-2300</td></tr><tr><td>Rhinoceros unicornis</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>1800-2700</td></tr></tbody></table>

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The smallest representative is the earliest lophiodontid species *Lophiaspis maurettei*, with body mass estimates near 40 kg (mean from 36 to 47.7 kg depending on the proxy; Table 3). Both *Eolophiodon* species have a body mass around 100 kg, with *Eolophiodon* sp. of Sainte-Eulalie having mean estimates ranging from 70.9 to 109.6 kg and *E. laboriense* from 99.3 to 157.5 kg depending on the *locus* studied and the equation applied. The *Lophiodon* species display bigger body mass, but the intra-generic disparity is huge. Indeed, *L. lautricense* (mean body mass for all proxies: 2319.2 kg) is ten times bigger than the older *L. cf. leptorhynchum* (mean body mass for all proxies: 220 kg; Table 3). The body mass seems to have increased with time within *Lophiodon*. For all species, the linear regression of Janis (1990) based on M2 gave the highest estimations of body mass, with values 16-43 % higher than the mean of all proxies (Table 3). Regarding the lowest estimations of body mass (12-25 % lower than the mean of all proxies), they were given by the linear regression of Legendre (1989) on m1 for *L. lautricense*, *L. tapirotherium*, and both *Eolophiodon*, and by that of Damuth (1990) on the m2 for *Ls. maurettei* and *L. (cf.) leptorhynchum*.

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## 4.2. Dental Microstructure

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We focus our description on vertical sections of the enamel belonging to five lophiodontid species (Table 1; Figure 3A-E). Only *Ls. maurettei* can clearly be discriminated by its *Schmelzmuster* (i.e., distribution of enamel types through enamel thickness), whereas the enamel of the younger lophiodontids looks more similar. Indeed, in *Ls. maurettei*, the enamel thickness on cuspid flank is measured at 774.8 ± 21.0 µm (Table 4). The *Schmelzmuster* comprises three zones (Figure 3E). Hunter-Schreger bands (HSB) are present over more than three quarters of the enamel thickness (81 to 92%), outer radial enamel (ORE) is present with a layer of approximately 0 to 3.4%, while inner radial enamel (IRE) represents a layer of 9.7 to 14.7%. They show low decussation angles but with large transition zones (~12.8 µm), which gives an ill-defined appearance to the bands. The HSBs come straight from the enamel-dentine junction (EDJ), and are very thin (~33.3 µm) and have an overall irregular
374

appearance. These bands form an angle of 74.8° with the EDJ. The diameter of the prisms varies across the enamel (3.8 ± 0.5 µm). The prisms form an angle of between 45 and 58° with the EDJ. The inter-prismatic matrix (IPM) appears as a reduced or absent sheath around the prisms.

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

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<caption>Figure 3: Enamel microstructure of Lophiodontidae</caption>

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The vertical sections studied show the whole *Schmelzmuster* (i.e., distribution of enamel types through enamel thickness) from the enamel dentine junction (EDJ) to outer enamel surface (OES) of A - *L. lautricense* (UM-ENAM 702A), B - *L. leutorhynchum* (UM-ENAM 729), C - *L. tapirotherium* (UM-ENAM 733), D - *E. laboriense* (UM-ENAM 740) and E - *Ls. maurettei* (UM-ENAM 743). F-G - details of the enamel illustrating distribution of the inter prismatic matrix (IPM) around the prism in coat or interrow-
sheet (IS) in *L. lautricense* (F – UM-ENAM 718 and G – UM- ENAM 722). Abbreviations: *L.* – *Lophiodon*,
*Ls.* – *Lophiaspis*.

Regarding all other lophiodontids (*Eolophiodon* and *Lophiodon* spp.), maximal enamel thickness
on cuspid flank is the most variable parameters (Table 4) from ~1266.6 ± 6.1 µm in *L. tapirotherium* to
~2636.2 ± 26.3 µm in *L. lautricense*. The *Schmelzmuster* of these taxa are characterized by three zones
among which the main developed zone comprises the HSB, with an extension of 80.6-98.8% of enamel
thickness (Figure 3A-D). The IRE is always present but never developed as in *Ls. maurettei*, being only
comprised between 1.5-4.8%. The ORE can be very developed and depends on the wear stage of the
tooth. We measured thick ORE in a lower molar of *L. leptorhynchum* (max 16.7%), but it appears
reduced to at least 4% most of the time, except in *L. lautricense* where ORE is always inferior to 4%.
The HSB are straight in *E. laboriense* (Figure 3D) and bent in *Lophiodon* spp. (Figure 3A-C) except for
a m3 of *L. lautricense* (straight course), highlighting the possible intra-specific variation of this character.
We can observe high variability in terms of anastomosis and bifurcation of HSB in various proportion in
our sample, ranging from absent in *L. tapirotherium* (Figure 3C) to numerous in *L. leptorhynchum* (Figure
3B; Table 4). The angle of the HSB with EDJ is variable within *L. lautricense* from 40.8° to 88.5° and is
thus not relevant for comparisons. The HSB are well delimited with clear transitional zone underlining a
high decussation angle between the bands close to 90° (Figure 3A). The IPM is relatively thicker than
in *Ls. maurettei*, but precise measurements of this difference cannot be obtained due to changing
orientations. The IPM forms thin sheath over the prism all along the enamel thickness (Figure 3G) and
is sometimes developed in thin interrow sheet in the HSB zone of *L. lautricense* (Figure 3F).

In absolute value, the enamel thickness of the studied lophiodontid molars doubles or even
triples over Eocene times, however, when molar size is taken into account, the relative enamel thickness
considerably decreases instead. Indeed, enamel thickness ratio relative to the size of occlusal area
(length * breadth) decrease from 3.86 in *Ls maurettei* to < 1 in *L. lautricense* (Table 4).
411 Table 4: Parameters of the enamel microstructure in the studied lophiodontids.

412 Abbreviations: Anast. – anastomosis, Bifurc. – bifurcation, ORE – outer radial enamel, IRE – inner radial enamel, HSB – Hunter-Schreger bands, EDJ – enamel-

413 dentine junction, IS – interrow sheet.

<table><thead><tr><th rowspan="2">Species</th><th rowspan="2">Tooth</th><th rowspan="2">Section</th><th rowspan="2">Slice number</th><th colspan="3">Schmelzmuster</th><th colspan="3">HSB</th><th rowspan="2">Angle with EDJ (°)</th><th rowspan="2">Orientation</th><th rowspan="2">Division of HSBs</th><th colspan="2">Prism</th><th colspan="2">IPM</th></tr><tr><th>Thickness (µm)</th><th>relative thickness (T/(L*W))</th><th>ORE (%)</th><th>IRE (%)</th><th>HSB (%)</th><th>Parazone width (µm)</th><th>Diazone width (µm)</th><th>Externe</th><th>Angle EDJ (°)</th><th>Inner</th><th>Outer</th></tr></thead><tbody><tr><td rowspan="5">L. lautricense</td><td rowspan="5">left M2 or M3</td><td>Mesial protocone</td><td>UM-ENAM 702 A</td><td>2636.2 ± 26.3</td><td>0.850</td><td>3.1</td><td>3.1</td><td>95.7</td><td>114.4 ± 9.9</td><td>24.4 ± 2.8</td><td>55.9</td><td>Bent</td><td>Bifurc.</td><td>4.6 ± 0.2</td><td>55.5</td><td>Coat</td><td>Coat</td></tr><tr><td>Distal protocone</td><td>UM-ENAM 702 B</td><td>2449 ± 14.4</td><td>0.789</td><td>1.4</td><td>1.7</td><td>96.2</td><td>122.8 ± 12.8</td><td>29.34 ± 5.5</td><td>68.4</td><td>Bent</td><td>Anast. Bifurc.</td><td>4.1 ± 0.5</td><td>67.9</td><td>Coat</td><td>Coat</td></tr><tr><td>Mesial protoloph</td><td>UM-ENAM 703</td><td>1757.2 ± 68.4</td><td>0.566</td><td>0.9</td><td>1.8</td><td>98.8</td><td>82.5 ± 15.3</td><td>28.5 ± 7.3</td><td>40.8</td><td>Bent</td><td>-</td><td>4.3 ± 0.9</td><td>50.6</td><td>Coat</td><td>Coat</td></tr><tr><td>Distal protoloph</td><td>UM-ENAM 704</td><td>1927.4 ± 21.3</td><td>0.621</td><td>0.6</td><td>2.2</td><td>96.7</td><td>74 ± 16.2</td><td>20.3 ± 4.9</td><td>49.1</td><td>Bent</td><td>-</td><td>3.7 ± 0.5</td><td>86.5</td><td>Coat</td><td>Coat</td></tr><tr><td>Protolophid</td><td>UM-ENAM 718</td><td>2429.6 ± 20.3</td><td>0.920</td><td>3.4</td><td>2.4</td><td>93.6</td><td>80.2 ± 8.9</td><td>24.5 ± 2.5</td><td>66.6</td><td>Straight</td><td>Bifurc.</td><td>4.0 ± 0.5</td><td>74.9</td><td>IS</td><td>Coat</td></tr><tr><td rowspan="3">L. lautricense</td><td rowspan="3">right M3</td><td>Protolophid</td><td>UM-ENAM 719</td><td>2422 ± 87.6</td><td>0.923</td><td>3.5</td><td>1.5</td><td>93.6</td><td>111.9 ± 16.7</td><td>21.0 ± 2.3</td><td>88.5</td><td>Straight</td><td>Anast. Bifurc.</td><td>3.2 ± 0.7</td><td>45.9</td><td>IS</td><td>Coat</td></tr><tr><td>Protoconid</td><td>UM-ENAM 722</td><td>2017.8 ± 26.8</td><td>0.767</td><td>1.9</td><td>1.8</td><td>94.4</td><td>119.8 ± 20.3</td><td>26.8 ± 2.4</td><td>83.8</td><td>Straight</td><td>Bifurc.</td><td>3.9 ± 0.4</td><td>48.1</td><td>Coat</td><td>Coat</td></tr><tr><td>Paracone</td><td>UM-ENAM 723</td><td>2336.2 ± 32.9</td><td>0.753</td><td>12</td><td>2.3</td><td>84.1</td><td>96.5 ± 3.1</td><td>17 ± 2.7</td><td>60.1</td><td>Bent</td><td>Anast. Bifurc.</td><td>4.5 ± 0.2</td><td>56.5</td><td>IS</td><td>Coat</td></tr><tr><td rowspan="2">L. lautricense</td><td rowspan="2">left M2 or M3</td><td>Mesial protocone</td><td>UM-ENAM 725A1</td><td>2611.2 ± 15.3</td><td>0.842</td><td>0</td><td>3.1</td><td>96.9</td><td>97.3 ± 9.1</td><td>19.6 ± 3.5</td><td>56.2</td><td>Bent</td><td>Anast.</td><td>5.1 ± 0.3</td><td>66.1</td><td>Coat/IS</td><td>Coat</td></tr><tr><td>Distal protocone</td><td>UM-ENAM 725A2</td><td>1421 ± 10.6</td><td>0.458</td><td>0</td><td>3.4</td><td>97.1</td><td>81.4 ± 10.3</td><td>22.1 ± 6.9</td><td>68.9</td><td>Bent</td><td>Anast.</td><td>4.6 ± 0.4</td><td>56.6</td><td>Coat/IS</td><td>Coat</td></tr></tbody></table>
<table><tbody><tr><td></td><td></td><td>Hypocone</td><td>UM-ENAM 725B</td><td>1414.6 ± 9.8</td><td>0.456</td><td>0</td><td>3.4</td><td>96.8</td><td>82.8 ± 9.5</td><td>18.8 ± 2.9</td><td>74.2</td><td>Bent</td><td>Anast.</td><td>4.7 ± 0.5</td><td>39.5</td><td>Coat</td><td>Coat</td></tr><tr><td>L. leptorhynchum</td><td>m indet</td><td>Protoconid</td><td>UM-ENAM 729</td><td>2357.8 ± 57.9</td><td>5.344</td><td>16.7</td><td>3.2</td><td>80.6</td><td>69.1 ± 11.9</td><td>12.6 ± 2.8</td><td>78.8</td><td>Bent</td><td>Anast. Bifurc.</td><td>4.0 ± 0.4</td><td>67.4</td><td>Coat</td><td>Coat</td></tr><tr><td>L. leptorhynchum</td><td>M indet</td><td>Protocone</td><td>UM-ENAM 731</td><td>1571.2 ± 54.8</td><td>1.656</td><td>0</td><td>4.8</td><td>92.5</td><td>84.3 ± 13.2</td><td>16.0 ± 1.1</td><td>-</td><td>Bent</td><td>Anast. Bifurc.</td><td>5.0 ± 0.3</td><td>61.5</td><td>Coat</td><td>Coat</td></tr><tr><td>L. cf. tapirotherium</td><td>M indet</td><td>Paracone</td><td>UM-ENAM 733</td><td>1266.6 ± 6.1</td><td>1.160</td><td>4.2</td><td>4.8</td><td>90.7</td><td>72.5 ± 9.4</td><td>11.4 ± 2.6</td><td>57.3</td><td>Bent</td><td>-</td><td>5.0 ± 0.4</td><td>74</td><td>Coat</td><td>Coat</td></tr><tr><td>E. laboriense</td><td>left M2</td><td>Mesial protocone</td><td>UM-ENAM 741</td><td>1518.4 ± 7.4</td><td>2.593</td><td>4.7</td><td>3.5</td><td>91.7</td><td>76.5 ± 10.1</td><td>18.8 ± 2.0</td><td>82.7</td><td>Straight</td><td>Anast.</td><td>4.1 ± 0.4</td><td>64.3</td><td>Coat</td><td>Coat</td></tr><tr><td>Ls. maurettei</td><td>left M</td><td>Distal protocone</td><td>UM-ENAM 743</td><td>774.8 ± 21.0</td><td>3.860</td><td>0</td><td>9.7</td><td>92.3</td><td>33.3 ± 9.1</td><td>12.8 ± 1.2</td><td>74.8</td><td>Straight</td><td>Bifurc.</td><td>4.4 ± 0.4</td><td>58.4</td><td>Coat to Absent</td><td>Coat to Absent</td></tr></tbody></table>
## 4.3. Mesowear

The mesowear of all species but *L. lautricense* (Robiac) is very similar, with a dominance of high relief (66.7 to 100 % of specimens) and rounded cusps (73.3 to 100 % of specimens) and a median (mesowear ruler) equals to 2 (Table 5). Some slight differences can still be noted for mesowear within our dataset. At Aumelas, the specimens of *L. leptorhynchum* displayed less high relief (66.67 %) and the only blunt cusp of the dataset (Table 5; Supplementary 1), although this could be due to age of the available specimens. In Sainte-Eulalie, the median is slightly higher (2.5) but this could be due to a sampling bias (n = 4; Table 5). The mesowear of the giant-sized *L. lautricense* suggests more abrasion, with a dominance of low relief (75 % of specimens) and rounded cusps (100 % of specimens; Table 5) and mesowear scores shifted towards higher values (Figure 4). A Kruskall-Wallis test highlighted an effect of body mass on the mesowear (chi-squared = 6.5346, df = 2, p-value = 0.03811) between *L. lautricense* (giant-sized) and the other lophiodon species (small to medium body mass).

<caption>Table 5: Mesowear analyses of the lophiodontids from Southern France.</caption>

Abbreviations: *L.* – *Lophiodon*, *Ls.* – *Lophiaspis*, Mad - median absolute deviation.

<table><thead><tr><th rowspan="2"></th><th rowspan="2"></th><th rowspan="2">N</th><th colspan="2">Occlusal relief</th><th colspan="3">Cusp Shape</th><th colspan="2">Mesowear Ruler</th></tr><tr><th>%High</th><th>%Low</th><th>%Sharp</th><th>%Round</th><th>%Blunt</th><th>Median</th><th>Mad</th></tr></thead><tbody><tr><td>Robiac</td><td><i>L. lautricense</i></td><td>12</td><td>25.00</td><td>75.00</td><td>0.00</td><td>100.00</td><td>0.00</td><td>3.00</td><td>1.48</td></tr><tr><td>Saint-Martin-de-Londres</td><td><i>L. tapirotherium</i></td><td>8</td><td>87.50</td><td>12.50</td><td>0.00</td><td>100.00</td><td>0.00</td><td>2.00</td><td>0.00</td></tr><tr><td>Aumelas</td><td><i>L. leptorhynchum</i></td><td>15</td><td>66.67</td><td>33.33</td><td>20.00</td><td>73.33</td><td>6.67</td><td>2.00</td><td>1.48</td></tr><tr><td>Naples 2</td><td><i>L. cf. leptorhynchum</i></td><td>6</td><td>100.00</td><td>0.00</td><td>0.00</td><td>100.00</td><td>0.00</td><td>2.00</td><td>0.00</td></tr><tr><td>Sainte-Eulalie</td><td><i>Eolophiodon sp.</i></td><td>4</td><td>100.00</td><td>0.00</td><td>25.00</td><td>75.00</td><td>0.00</td><td>2.50</td><td>0.74</td></tr><tr><td>La Borie</td><td><i>E. laboriense</i></td><td>14</td><td>85.71</td><td>14.29</td><td>21.43</td><td>78.57</td><td>0.00</td><td>2.00</td><td>0.00</td></tr><tr><td>Palette</td><td><i>Ls. maurettei</i></td><td>5</td><td>80.00</td><td>20.00</td><td>20.00</td><td>80.00</td><td>0.00</td><td>2.00</td><td>0.00</td></tr></tbody></table>
<figure><img src="image_5.png" /><figcaption>Figure 4: Barplots of individual mesowear ruler scores by locality.</figcaption></figure>

SMF – Saint-Martin-de-Londres. Mesowear scores were obtained using the mesowear ruler (Mihlbachler et al., 2011). Red dash lines indicate median for each locality.

4.4. Dental Microwear Texture Analysis of the lophiodontids from Southern France and comparison to extant perissodactyl species

We calculated the mean, standard deviation and median for anisotropy (Str), complexity (Asfc), and heterogeneity of the complexity (HAsfc9 and HAsfc81) by species and compared them to the recent perissodactyla dataset (rhinoceroses and Brazilian tapir). The results are presented in Table 6. There was no clear cluster of microwear texture by species in the lophiodontid dataset (MANOVA: p-value = 0.05359) and the distribution of specimens was wide and overlapping (Figure 5). Values of Asfc were mostly low to moderate (< 2), but several specimens reached high (> 2) to very high values (> 5), notably one specimen from Sainte-Eulalie (Eolophiodon sp.), two from Naples 2 (L. cf. lektorhychum) and two from Saint-Martin-de-Londres (L. tapirotherium), suggesting the consumption of hard objects (seeds or shelled fruits). There was a trend toward increasing values through time from a median value of 0.87 at La Borie to 2.02 at Robiac (Table 6). The L. lektorhynchum specimens from Aumelas were an exception to this increasing Asfc trend, and displayed a median Asfc of 0.51, suggesting the consumption of soft items. Concerning Str, the disparity was important, with no clear tendency by species nor by genus (Figure 5). The Str values observed for all lophiodontid species were largely outside of the range for extant species (Table 6; Figure 6), suggesting the consumption of less abrasive food items.
451

<caption>Table 6: Lophiodontids and extant species dental microwear texture: median, mean and standard deviation of the mean (SD) of textural parameters by species.</caption>

452

453

Asfc (area-scale fractal complexity; complexity), Str (inverse of anisotropy), HAsfc (heterogeneity of area-scale fractal complexity).

454

<table><thead><tr><th rowspan="2"></th><th rowspan="2"></th><th rowspan="2">N</th><th colspan="3">Asfc</th><th colspan="3">Str (s = 0.5)</th><th colspan="3">HAsfc9</th><th colspan="3">HAsfc81</th></tr><tr><th>Median</th><th>Mean</th><th>SD</th><th>Median</th><th>Mean</th><th>SD</th><th>Median</th><th>Mean</th><th>SD</th><th>Median</th><th>Mean</th><th>SD</th></tr></thead><tbody><tr><td rowspan="2">Robiac</td><td><i>L. lautricense</i></td><td>8</td><td>2.02</td><td>2.03</td><td>1.15</td><td>0.43</td><td>0.56</td><td>0.21</td><td>0.37</td><td>0.37</td><td>0.11</td><td>0.82</td><td>0.83</td><td>0.33</td></tr><tr><td><i>L. tapirotherium</i></td><td>4</td><td>5.92</td><td>5.96</td><td>5.73</td><td>0.64</td><td>0.69</td><td>0.11</td><td>0.47</td><td>0.44</td><td>0.18</td><td>0.79</td><td>0.74</td><td>0.19</td></tr><tr><td>Aumelas</td><td><i>L. leptorhynchum</i></td><td>6</td><td>0.51</td><td>1.08</td><td>1.23</td><td>0.72</td><td>0.62</td><td>0.24</td><td>0.43</td><td>0.43</td><td>0.19</td><td>0.58</td><td>0.68</td><td>0.36</td></tr><tr><td>Naples 2</td><td><i>L. cf. leptorhynchum</i></td><td>12</td><td>1.45</td><td>2.24</td><td>1.91</td><td>0.65</td><td>0.64</td><td>0.15</td><td>0.55</td><td>0.81</td><td>0.68</td><td>1.19</td><td>1.84</td><td>1.33</td></tr><tr><td>Sainte-Eulalie</td><td><i>Eolophiodon sp.</i></td><td>4</td><td>1.36</td><td>2.01</td><td>2.09</td><td>0.44</td><td>0.53</td><td>0.25</td><td>0.84</td><td>1.01</td><td>0.47</td><td>0.63</td><td>0.57</td><td>0.28</td></tr><tr><td>La Borie</td><td><i>E. laboriense</i></td><td>10</td><td>0.87</td><td>1.18</td><td>0.72</td><td>0.2</td><td>0.3</td><td>0.21</td><td>0.54</td><td>0.64</td><td>0.28</td><td>0.52</td><td>0.54</td><td>0.2</td></tr><tr><td>Recent</td><td><i>Tapirus terrestris</i></td><td>15</td><td>1.21</td><td>1.3</td><td>0.54</td><td>0.24</td><td>0.24</td><td>0.23</td><td>0.27</td><td>0.28</td><td>0.15</td><td>0.48</td><td>0.54</td><td>0.23</td></tr><tr><td>Recent</td><td><i>Ceratotherium simum</i></td><td>14</td><td>1.34</td><td>1.33</td><td>0.55</td><td>0.14</td><td>0.14</td><td>0.04</td><td>0.38</td><td>0.5</td><td>0.5</td><td>0.72</td><td>1</td><td>0.91</td></tr><tr><td>Recent</td><td><i>Diceros bicornis</i></td><td>16</td><td>1.26</td><td>1.41</td><td>0.73</td><td>0.14</td><td>0.16</td><td>0.07</td><td>0.29</td><td>0.39</td><td>0.22</td><td>0.67</td><td>0.77</td><td>0.26</td></tr><tr><td>Recent</td><td><i>Dicerorhinus sumatrensis</i></td><td>3</td><td>0.37</td><td>0.44</td><td>0.21</td><td>0.12</td><td>0.13</td><td>0.03</td><td>0.35</td><td>0.35</td><td>0.21</td><td>0.69</td><td>0.56</td><td>0.24</td></tr><tr><td>Recent</td><td><i>Rhinoceros sondaicus</i></td><td>14</td><td>1.84</td><td>1.91</td><td>1.27</td><td>0.16</td><td>0.16</td><td>0.07</td><td>0.36</td><td>0.38</td><td>0.16</td><td>0.74</td><td>0.8</td><td>0.25</td></tr><tr><td>Recent</td><td><i>Rhinoceros unicornis</i></td><td>4</td><td>2.15</td><td>2.36</td><td>2.04</td><td>0.24</td><td>0.22</td><td>0.08</td><td>0.38</td><td>0.35</td><td>0.17</td><td>0.73</td><td>0.76</td><td>0.48</td></tr></tbody></table>

455
<figure><img src="image_6.png" /><figcaption>Figure 5: Complexity against anisotropy for all specimens of lophiodontids with associated density plots by textural parameters.</figcaption></figure>

A

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

B

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

C

<figure><img src="image_9.png" /></figure>

D

<figure><img src="image_10.png" /><figcaption>Figure 6: Boxplots of DMTA parameters by species (left, lophiodontids; right, recent perissodactyl comparison sample).</figcaption></figure>
463 A – Str, B – Asfc, C – Hasfc9, D – Hasfc81

464 Letters above boxes corresponds to the groups according to Fisher's LSD post-hoc test.

465

466 Median values of Str values also increased from La Borie to Aumelas (median: 0.52 to 0.72 respectively) and then decreased in more recent localities, reaching the lowest values of the dataset at
467 Robiac (median: 0.43). Lastly, median values of HAsfc showed more differences between species
468 (ANOVA: p-values = 0.0199), from moderate at La Borie (HAsfc9: 0.2 and HAsfc81: 0.54) to very high
469 at Naples 2 (HAsfc9: 0.55 and HAsfc81: 1.19).
470

471

472 When compared to the extant dataset more differences arose (MANOVA by species: p-value = 3.61 x 10⁻¹⁶). To precise the differences, we conducted ANOVAs and associated post-hoc tests (for details see Supplementary 2). The ANOVAs by parameters revealed significant differences for all parameters (p-values between 0.0337 and 2 x 10⁻¹⁶). According to the post hoc tests (Tukey's HSD and Fisher's LSD), differences in Str are between extinct (higher values) and extant species (Figure 6). For Asfc, *L. tapirotherium* stood out from the other species (Figure 6), with notable differences to *D. sumatrensis* (HSD test: p-value = 0.0153) and *L. leptorhynchum* (HSD test: p-value = 0.0795). Eventually, regarding HAsfc, the differences were due to contrasting values for *L. cf. leptorhynchum* (Naples 2; Figure 6) compared to *E. laboriense* and to *T. terrestris* for both Hasfc, as well as to *L. leptorhynchum* (Aumelas) and to *D. sumatrensis* for HAsfc81 only.

482

483 **5. Discussion**

484

485 **5.1. Dietary inferences**

486 We studied dietary preferences at different scales through enamel microstructure and dental wear (meso- and micro- wear). The enamel microstructure gives insights into the macroevolutionary adaptation of teeth to the mechanical constraints of the diet (toughness, hardness; Koenigswald and Sander, 1997; Marivaux et al., 2022; Viglino et al., 2023). The *Schmelzmuster* of *Ls. maurettei*, with little radial enamel (Figure 3E; Table 4), suggests limited abrasion in the diet (Rensberger, 2000), consistent with the low mesowear scores (Figure 4; Table 5) and high Str (Figure 5; Figure 6; Table 6). The IPM forms thin sheath over the prisms, which indicates little specialisation similarly to other basal

492
perissodactyls (Koenigswald et al., 1987; Pfretzschner, 1988). The more decussated enamel observed in *Eolophiodon* and *Lophiodon* spp. indicates the consumption of harder food items, such as branches, bark or seeds. Indeed, the presence of HSB (decussated enamel) provides a greater resistance to the propagation of cracks allowing for the tolerance of greater mechanical constraints while chewing on hard objects (Pfretzschner, 1988; Rensberger, 1987). The interrow sheet observed in *L. lautricense* (Figure 3F) supposes the resistance to crack propagation and the beginning of an adaptation to a higher abrasion load (Koenigswald, 2014; Pfretzschner, 1988; Rensberger, 1987). This is consistent with the higher mesowear scores (Figure 4; Table 5) and lower Str (Figure 5; Figure 6; Table 6) observed for this species at Robiac. The modifications of the *Schmelzmuster* should however be regarded with caution, as it could also be the result of an allometric compensation for body mass increase, rather than a slow and limited adaptation to a tougher and harder diet (Koenigswald, 1980). Notably, the switch from straight HSB to bent trajectories (Figure 3A-C; Table 4) in more recent species (*Lophiodon*) could be related to the mass increase experienced by this taxa (Alloing-Séguier et al., 2014).

Similarly to enamel microstructure, there were little differences in the dental wear of the lophiodontids studied here. Indeed, the mesowear scores of all species are rather similar with a dominance of high relief and rounded cusps and a median equals to 2 suggesting browsing habits (Fortelius and Solounias, 2000; Rivals et al., 2020), except for the youngest and largest species *L. lautricense* (Figure 4; Table 5). The mesowear of *L. lautricense* indicates a more abrasive diet (lower relief, median: 3), consistent with the lowest values of Str observed for this species (Figure 5; Figure 6; Table 6). The microwear textures of the six species of lophiodontids studied fall in the range of the extant folivores (*D. sumatrensis* and *T. terrestris*) and browsers (*D. bicornis* and *R. sondaicus*; Figure 5; Figure 6). The low to moderate values of Asfc for all lophiodontids but *L. lautricense* and *L. tapirotherium*, suggest rather soft food items in the diet of the lophiodontids (Scott, 2012; Scott et al., 2006). A few specimens however, displayed high to very high values of Asfc, notably two of *L. tapirotherium*, indicating the consumption of hard objects such as branches, bark, and/or shelled fruits (Semprebon et al., 2011), perhaps indicative of variable food availability and/or seasonality to some extent. The high values of Str observed for the lophiodontids are outside of the range displayed by extant species (Figure 5; Figure 6; Table 6) and discard the ingestion of tough and abrasive objects (Francisco et al., 2018a). There was an increase in Str values between La Borie (*E. laboriense*) and Aumelas (*L. leporrhynchum*),
which denotes a decrease in the abrasion load of the diet. This might be due to a diversification of the diet switching from folivory to browsing with more lignified tissues. The values of HAsfc, indicative of dietary diversity at the individual scale (Ramdarshan et al., 2016; Scott, 2012), seem to concur with such a switch: HAsfc values are low at La Borie, similarly to what is found in modern folivores *D. sumatrensis* and *T. terrestris*, and moderate to high in other lophiodontids (Figure 6; Table 6). Furthermore, we observed a great variety in the individual microwear textures of all species (wide dispersion: Figure 5) suggesting some flexibility in the diet of these taxa, but also variable food availability locally and/or seasonality at a regional scale. This dietary diversity could be responsible for the huge intra-specific variation observed in the dental morphology of the lophiodontid species through a decrease of the selection pressure (Sudre, 1971; Vautrin et al., 2019).

Our results suggest a leaf-dominated diet for the lophiodontid samples studied here, and the exclusion of hard objects at least for the oldest and smallest taxa (*Lophiaspis, Eolophiodon*). These results differ from the typical reconstruction of basal perissodactyls as largely frugivore based on their dental morphology (Blondel, 2001; Saarinen, 2019 but see Wilde and Hellmund, 2010). Interestingly, the diets of other basal perissodactyls have already been investigated. For instance, the closely-related, contemporaneous, non-associated, basal chalicotherioids *Eomoropus* and *Litolophus*, display low magnification dental microwear patterns interpreted as a browsing signal (Semprebon et al., 2011). However, despite a dentition sharing some features with the lophiodontids, and a similar body size for *Litolophus* and *Eolophiodon*, the reconstructed diet of these chalicotherioids is considered fruit-dominated due to the deep symmetrical punctures of the enamel (Semprebon et al., 2011). A fruit-dominated diet is also inferred for the early equoid *Hyracotherium* (Solounias and Semprebon, 2002). This suggests that frugivory is probably the primitive condition in Perissodactyla, be it among Tapiromorpha or Hippomorpha, a hypothesis further supported by the brachydont and bunodont teeth of the Early Eocene *Cambaytherium* – considered as closely related to perissodactyls – adapted to a hard-fruit diet (Rose et al., 2019). Folivory probably evolved independently in the different clades of perissodactyls, in association with the trend towards a more lophodont and molarised morphology (Radinsky, 1969), like what is observed in more derived chalicotherioids (Semprebon et al., 2011) or in the in the Middle Eocene–Oligocene European *Plagiolophus* from the middle Eocene to the Oligocene (Perales-Gogenola et al., 2022).
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## 5.2. Influence of body mass and molarisation

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Our fossil dataset included one small species (*Ls. maurettei*: 40 kg), three medium species close to the body mass of extant *Tapirus terrestris* (150 to 300 kg; Table 3) – *Eolophiodon laboriense*, *Eolophiodon* sp., and *Lophiodon leptorhynchum* – one large species (*L. tapirotherium*: 480 kg), and one megaherbivore *sensu* Owen-Smith (1988) in the average range of *Ceratotherium simum* (1600-3600 kg) and in the upper range of *Rhinoceros unicornis* (1800-2700 kg; Table 3) – *L. lautricense*. The giant-sized *L. lautricense* seems to have been less selective and have included lower quality, more fibrous dietary items such as whole branches, bark, or even fruits. This less selective behavior is consistent with its larger body mass, as large living herbivores may consume a diet of lower nutritional quality (richer in lignin) due to their low metabolic requirements (Clauss et al., 2003; Owen-Smith, 1988), and a longer digestive tract allowing for a longer retention time to optimize digestion efficiency, as observed in modern rhinoceroses (Owen-Smith, 1988).

Another hypothesis that might explain the differences in *L. lautricense* is the greater degree of molarisation of the premolars (Figure 7). Indeed, molarisation results in a more homogeneous tooth row hence creating a more important chewing surface, which allows for a more efficient mastication (Clauss et al., 2009; Fletcher et al., 2010; Koenigswald, 2014) and for the consumption of tougher food items. In this respect, and coupled with the body mass increase, molarisation in lophiodontids may reflect a decrease in the quality of the diet with an incorporation of more fibrous plants. In lophiodontids, the lophs of the molars shear the food during the mastication, and the bolus is compressed against the ectoloph and the prehypocristid (Koenigswald, 2014). Thus, in the same phase of mastication, the plants are both sheared and crushed against the buccal side of the molar. This type of chewing is common in bilophodont mammals, like *Tapirus* (Koenigswald, 2014) and allows to extract a maximum of nutrients with a single phase of jaw movement. In basal lophiodontids, premolars would have had only a grinding role (Koenigswald, 2014). Furthermore, the main work of mastication is mainly concentrated on a single pair of teeth, first on the last premolars in juveniles, then migrating distally during the life of the animal (Koenigswald, 2014). Greater molarisation of premolars can thus allow more shearing during the lifetime of the animal. Moreover, the efficient chewing achieved by the more molarised dentition of *L. lautricense*
582 is consistent with the feeding strategy of large herbivores, allowing to compensate for the ingestion of
583 low quality and fibrous food, with a greater quantity ingested and a better extraction of nutrient.

584

585 **5.3. Influence of biotic and abiotic factors during the Palaeogene**

586 Besides diet, dental wear can also give insights into the habitat and environment of the studied
587 specimens. The dominance of folivore and browsing taxa suggests that they were living in environments
588 with a great abundance of trees and shrubs. Concerning La Borie (MP8+9; *E. laboriense*), the data from
589 the sediments, the fauna, and the flora point towards a palaeoenvironment of floodplain savannah under
590 a moist tropical climate (Laurent et al., 2010). At Robiac (MP16; *L. lautricense*), the flora and the
591 cenogram indicate a closed and humid forest similar to the extant African equatorial forest (Remy, 2015).
592 At the other localities studied here (Palette, Sainte-Eulalie, Naples 2, Aumelas, and Saint-Martin-de-
593 Londres), the climate and environment have not been properly investigated (study in preparation by
594 several of us). The alleged climate in Europe during the Ypresian (56-47.8 Ma) was tropical warm and
595 humid (Westerhold et al., 2020), suggesting rather similar environments at most localities studied. The
596 Lutetian (47.8-41.3 Ma) however, is characterized by colder temperatures than during the adjacent Early
597 Eocene Climatic Optimum (EECO: ~ 53-49 Ma) and Middle Eocene Climatic Optimum (MECO: ~ 40.5-
598 40 Ma, Figure 7; Speijer et al., 2020; Westerhold et al., 2020). Lutetian European environments are
599 reconstructed as more open and arid than during the climatic optimum period of the Early Eocene
600 (Franzen, 2003). Interestingly, mass increase and dietary changes in lophiodontids occurred during the
601 post-EECO cooling and the Lutetian (Figure 7), which is consistent with Bergmann's rule (Bergmann,
602 1847) postulating that homeotherms are larger in colder climates. Similar trends (body mass increase,
603 molarisation, and dietary changes) have occurred in several coeval perissodactyl taxa, notably in the
604 Deperetellidae and Helaletidae (Tapiroidea), the Paraceratheriidae (Rhinoceroidea) in the Middle
605 Eocene of Asia, or the Brontotheriidae in North America (Bai et al., 2018a, 2018b; Gong et al., 2020;
606 Sanisidro et al., 2023). For the latter, the timing of the body mass increase is strikingly similar to that
607 observed in the lophiodontids. Such trends are thought to have played a crucial role in the evolution of
608 this order, as they are often correlated with an opening of the environments and the inclusion of larger
609 amounts of low-quality food items in the diet (Butler, 1952; Radinsky, 1969).

610
Besides climatic changes, the faunal turnovers of the Eocene might also have played a critical role in the lophiodontid evolutionary history and notably in their extinction during the late Bartonian (Robinet et al., 2015). Indeed, the arrival of competitors such as the palaeotheres during the Middle Eocene (Danilo et al., 2013; Franzen, 2003), might be partly responsible for the niche shift (changes in body mass and dietary preferences) observed in lophiodontids at that time (Figure 7). The size and the diet of Middle-Late Eocene palaeotheres are very similar to that of the Ypresian lophiodons (Perales-Gogenola et al., 2022), which might have forced the more recent *Lophiodon* species into the consumption of lower quality fibrous items. Yet, competition for such a shifting resource over time can also be considered at a much broader scale, notably in the context of plant-small mammal and plant-insect interactions (Crawley, 1989; Dulamsuren et al., 2008; Kaplan and Denno, 2007).

621
<figure><img src="image_11.png" /><figcaption>Figure 7: Phylogeny of the lophiodontids with body mass estimations and dietary preferences plotted against the main climatic events of the Eocene.</figcaption></figure>

Climatic data from Westerhold et al. (2020). Abbreviations: PETM – Palaeogene-Eocene thermal maximum, ETM – Eocene thermal maximum, BC – Bridgerian Crash cooling, LLTM – Late Lutetian thermal maximum, MECO – Middle Eocene climatic optimum, EOT – Eocene-Oligocene transition. Figure adapted from Vautrin (2019).

## 6. Conclusion

This unprecedented work on lophiodontids' diet revealed that they were folivores and browsers during their whole evolutionary history, which contradicts the typical view of basal perissodactyls as frugivores. Changes in body size and molarisation of the premolars seemed to have provided for a greater food tolerance (lower nutritional quality, tougher/harder items) rather than resulting in a drastic
636 dietary change. This study highlighted the potential of our database on tapir and rhinoceros microwear,
637 to reconstruct the diet of extinct related taxa even outside of the Ceratomorpha. This opens a wide scope
638 of wear studies that could reinvestigate the diet of other lophodont perissodactyl species such as
639 brontotheres or chalicotheres, but also other extinct panperissodactyls, such as long-lived South
640 American notoungulates (Palaeocene–Holocene).

641

642 CRediT authorship contribution statement

643 **Manon Hullot:** Methodology, Formal analysis, Investigation, Writing – Original Draft, Visualization,
644 **Céline Robinet:** Methodology, Investigation, Writing - Review & Editing, **Quentin Vautrin:**
645 Methodology, Investigation, Writing – Original Draft, Visualization, **Rodolphe Tabuce:**
646 Conceptualization, Methodology, Writing - Review & Editing, Supervision, Funding acquisition, **Pierre-**
647 **Olivier Antoine:** Conceptualization, Writing - Review & Editing, Supervision, Funding acquisition,
648 **Gildas Merceron:** Conceptualization, Methodology, Validation, Resources, Writing - Review & Editing,
649 Supervision, Funding acquisition, **Fabrice Lihoreau:** Conceptualization, Methodology, Validation,
650 Writing – Original Draft, Writing - Review & Editing, Visualization, Supervision, Funding acquisition.

651

652 Acknowledgements

653 We are indebted to the curators of all the visited institutions for granting access to the collections
654 they are in charge of: S. Jiquel, B. Marandat and A.-L. Charruault (University of Montpellier), D. Berthet
655 and F. Vigouroux (Musée des Confluences de Lyon), F. Zachos and A. Bibl (Natuhistorisches Museum
656 Wien), J. Lesur and V. Bouetel (Muséum National d'Histoire Naturelle, Paris), M. Lowe (University
657 Museum of Zoology of Cambridge), E. Gilissen (Musée Royal d'Afrique Centrale, Tervuren), L. Costeur
658 (Natuhistorisches Museum Basel), P. Dalous and Y. Laurent (Muséum d'Histoire Naturelle de
659 Toulouse), I. Olivares (Museo de La Plata), Y. Dutour and N. Vialle (Muséum d'Histoire Naturelle d'Aix-
660 en-Provence), J. Philip (Université d'Aix-Marseille), E. Robert (Université Lyon 1 – Claude Bernard). We
661 are also grateful to late H. P. Labarrère, to B. Soumeille and D. Vidalenc for the donation of some
662 specimens included in this study. We would like to thank F. Guéret who initiated the study of the enamel
663 microstructure in Lophiodontidae during his master thesis in Montpellier and D. Cot from the Institut
664 Européen des Membranes de Montpellier for access to SEM facility. The authors thank J. Surault from
665 the Paleovoprim Lab who contributed to the dental microwear surface acquisition. This research was
666 partly funded by the ANR EDENs programme 20-CE02-0007.

667

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