than the m3, but the new report of m4 of *Pd. crocheti* sp. nov. and *Pd. russelli* in the present study shows that it is the same for these species. Altogether, none of the characters proposed by Crochet (1979, 1980b) are diagnostic of *Pd. louisi*; they are either actually not observed on the material, or are plesiomorphies. However, *Peradectes louisi* is definitely distinct from all other peradectid species in combining a stylar cusp D located distolabially to the metacone on the stylar shelf of M3, a stylar cusp C relatively lower than the stylar cusp D on M1-M3, and relatively long m3 with subequal entoconid and hypoconulid.

With the exception of the peradectid M2 from Coulondres (Southern France, ~MP10; UM-CLR-1; Crochet 1980b: fig. 28), the m1 MNHN.F.CB3021 here referred to *Pd. russelli* (interpreted as a dp3 by Crochet 1980b), and one possible m4 not found in collections (see Crochet 1980b: p. 49, bottom), all molars attributed to *Peradectes* sp. (Crochet 1980b: p. 49-51, figs. 26-27, 29) are here better allocated to *Pd. louisi*. According to Crochet (1980b: p. 49), two worn and fragmentary lower molar rows (MNHN.F.Av4642 and MNHN.F.CB226, Figs. 11i-j) differ from *Pd. louisi* in having a talonid with a rectilinear lingual edge and a hypoconulid more lingually positioned, hence characters for which a lingual axis of reference is needed to relatively locate structures. However, on both specimens the metaconid is totally worn (MNHN.F.Av4642, Fig. 11i) or incomplete (MNHN.F.CB226, Fig. 11j) on m3, the best preserved molar of each row, which probably prevented Crochet (1980b: fig. 29b) from describing them with an accurate orientation. With a corrected orientation, these specimens resemble *Pd. louisi*, with a subequal entoconid and hypoconulid on a relatively long m3. The differences in shape of the entoconid and cristid obliqua pointed out by Crochet (1980b) have been shown here to be typical variable traits of *Pd. louisi* (Fig. 11). All differences noted by Crochet (1980b) between upper molars of *Peradectes* sp. and *Pd. louisi*, such as the doubling of stylar cusp C on one specimen (Crochet 1980b: fig. 27), or the small size of stylar cusp D (Fig. 10i-j) are here interpreted as variable features of *Pd. louisi*. In fact, the doubling of stylar
cusp C is known to be as rare in other *Peradectes* species with various upper molars described, namely *Pd. coprexeches* (Williamson and Taylor 2011: p. 13, fig. 6.2) and *Pd. crocheti* sp. nov. (a single specimen concerned; this study). Note that the doubling of stylar cusp C is probably more frequent in *Mimoperadectes* (see Comparative description of *Pd. crocheti* sp. nov.), and in the oldest *Peradectes* species, *Pd. minor* (Clemens 2006: p. 28), than in other peradectid species.

**Larger European peradectids, *Peradectes russelli* versus *Peradectes mutigniensis*'.** Based on their original diagnoses (Crochet 1979) and comparisons (Crochet 1980b: p. 52), *Pd. russelli* and *Pd. mutigniensis* would appear to differ in possessing (i) M3 relatively wider for *Pd. mutigniensis* (i.e., with a mesiodistally shorter centrocrista and ectoflexus), (ii) M3 with a symmetric versus asymmetric ectoflexus, (iii) a lingual opening of the trigonid basin higher versus not higher than the lingual opening of the talonid basin (metaconid-entoconid notch) on lower molars and (iv) a less curved cristid obliqua on m2 and m3 of *Pd. mutigniensis*. We disagree with these four arguments. First, the length to width ratio here calculated for M3 reported by Crochet (1980b) to both species are similar (Online Resource 1: Table S3). In particular this ratio is almost identical for the M3 of the holotype of *Pd. russelli* (MNHN.F.CB924, L/W = 0.79) and the 'holotype' of *Pd. mutigniensis* (MNHN.F.Mu5521, L/W = 0.78). Second, the ectoflexus of the M3 of the holotype of *Pd. russelli* and all specimens originally attributed to this species is asymmetric, with a metastylar wing more labially expanded, when the paracone and metacone are aligned (e.g., MNHN.F.CB2502, Fig. 12h). Third, as in all peradectids, the trigonid basin of lower molars of *Pd. mutigniensis* actually opens higher lingually than the talonid basin (e.g., MNHN.F.Mu18000, Fig. 12m). Fourth, although the single m3 of *Pd. mutigniensis* has effectively a weakly curved cristid obliqua (MNHN.F.Mu6451; Crochet 1980b: fig. 24), a variation in the curvature of this cristid has been noted in the coeval *Pd. louisi*. It is worth mentioning that molars originally attributed to *Pd*.
russelli are slightly larger or subequal in size to those of *Pd. 'mutigniensis'* (Online Resource 1: Table S3), with one exception (the M3 MNHN.F.CB742 of *Pd. 'mutigniensis'* is larger than the M3 MNHN.F.Av4813 of *Pd. russelli sensu Crochet* [1980b]). Altogether, all characters proposed by Crochet (1979, 1980b) to distinguish *Pd. russelli* from *Pd. 'mutigniensis'* either are not observed on the concerned specimens or represent intraspecific morphological variation. The species name *Peradectes russelli* has page priority and is thus valid over its junior synonym *Pd. 'mutigniensis'* (see Crochet 1979: p. 367-368). Morphological variation found in molars of *Pd. russelli* are here documented, as for other European *Peradectes* species. Notably, some M1 to M3 of *Pd. russelli* have a transverse accessory crista on their stylar shelf, lingual to stylar cusp D (see Comparative description of *Pd. russelli*). This reminds the recent observation of transverse cristae variably present between the metacone and stylar cusp D in various herpetotheriid species (Wessels et al. 2024: p. 15, figs. 3h-j, 6a).

Crochet (1980b: p. 52, tables 4-5) argued that m4 of *Pd. russelli* and *Pd. 'mutigniensis'* are larger than m3. Among the collections of the MNHN, two specimens interpreted as m4 of *Pd. russelli* by Crochet (1980b: table 4) were found, namely MNHN.F.CB5114 from Condé-en-Brie and MNHN.F.Av9019 from Avenay. However, the lingual edge of their talonid is straight, and their talonid is relatively mesiodistally longer than in ascertained European metatherian m4. MNHN.F.CB5114 also exhibits as high protoconid and metaconid. MNHN.F.CB5114 and MNHN.F.Av9019 are most likely respectively m2 and m3 of an eutherian mammal taxon that lacks the paraconid keel of metatherians. We did not find the figured m4 specimen of *Pd. russelli* (Crochet 1980b: fig. 18) in the collections, but it is more similar to a herpetotheriid than to a peradectid metatherian considering characters such as the lingual alignment of the paraconid, metaconid and entoconid with a straight distolingual edge of the talonid, the transversally aligned protoconid and metaconid, and the mesiodistally long entoconid (Table 6). The two specimens reported as m4 of *Pd. 'mutigniensis'* by Crochet (1980b: table 5, fig.
25), MNHN.F.CB5100 and MNHN.F.GL92, lack the relative labiolingual reduction of the talonid compared to the other lower molar loci, which is a characteristic of m4 of most marsupialiforms. MNHN.F.CB5100 and MNHN.F.GL92 are here better interpreted as m2 of *Pd. russelli*, given the relative width of their trigonid and talonid. The single true isolated m4 of *Pd. russelli* is the newly reported MNHN.F.Mu18003 (Fig. 12u-v), which is subequal in length and shorter, respectively, than the two ascertained m3 of *Pd. russelli*.

**Paleoecological and biostratigraphic implications.** *Peradectes louisi* and *Pd. russelli* are coeval and are the only two peradectid species in MP8+9 and ~MP8+9 localities from the Paris Basin (Avenay, Condé-en-Brie, Mutigny, Sables de Brasles and Sézanne-Broyes), while Crochet (1980b) recognized up to four *Peradectes* species (*Pd. louisi*, *Pd. russelli*, *Pd. mutigniensis* and *Peradectes* sp.) in Avenay and Condé-en-Brie. *Peradectes louisi* and *Pd. russelli* represent two distinct species that differ in a few morphological characters in addition to size difference, namely in the proportions of their lower molars (Table 5), and in two discrete features, namely the relative positioning of stylar cusp D on M3, and the relative ventral extension of stylar cusps C and D on M1 and M2 (Fig. 10 vs Fig. 12). Because the area of stylar cusps C and D is known to have minor functional importance during molar occlusion (e.g., Crompton and Hiiemae 1970: fig. 5A; Crochet 1980a: fig. 2a; Davis 2011: fig. 1B; Wessels et al. 2024: p. 15, fig. 8b) and because *Pd. louisi* and *Pd. russelli* group into two distinct size clusters (Fig. 13), these two species could probably partition their ecological niches (hypothetical arboreal and insectivorous to frugivorous small mammals, as partly deduced from the peradectid-like taxon from Messel; Kurz 2005) mostly based on size (body masses estimated to 22.9 – 31.4 g for *Pd. louisi*, and 41.2 – 60.6 g for *Pd. russelli*, using lengths of the unworn M3 [Online Resource 1: Tables S2-S3] in the appropriate predictive equation of Gordon [2003: fig. 7]). Similar cases of sympatry in the MP8+9 and ~MP8+9 mammal faunas studied, between two morphologically similar species that differ in size, concern other taxa, such as
(among recent revisions) the plesiadapiform *Arcius*, because *Arc. fuscus* and the larger *Arc. lapparenti* co-occur in Mutigny, Avenay, Condé-en-Brie, Sables de Brasles, and Sézanne-Broyes (López-Torres and Silcox 2018), and the theridomorph rodent *Euromys*, because *E. thaleri* (Michaux, 1964) and the larger *E. woodi* (Michaux, 1964) co-occur in Mutigny, Avenay and Condé-en-Brie (Escarguel 1999; Vianey-Liaud and Marivaux 2021). The coexistence of two peradectid species differing in size apparently continues during the EECO (~MP10; Vianey-Liaud et al. 2024).

European peradectid species larger than the small *Pd. crocheti* sp. nov. first occur in Mutigny (~MP8+9, PE IV), with *Pd. russelli*. The mammalian faunas of Mutigny and Avenay are considered to exhibit major differences based on two herpetotheriid lineages, still unrevised, following the conclusions of Crochet (1980b) (Schmidt-Kittler et al. 1987: p. 21), and also on the absence of *Pd. russelli sensu Crochet (1980b)* in Mutigny (Crochet 1980b: fig. 30). This difference in faunal composition is here reduced because *Pd. russelli* is recorded in both localities, and molars of this species from Mutigny, such as M1, do not significantly differ in size from *Pd. russelli* of other MP8+9 and ~MP8+9 localities (Online Resource 1: Table S3).

**Revision of putative occurrences of typical MP8+9 and ~MP8+9 peradectids in MP10 and ~MP10 faunas**

*Peradectes louisi* was recorded in Grauves (MP10) by two isolated lower molars which were not described (Crochet 1980b: table 3). The right m1 MNHN.F.Gr10010 is completely worn. This specimen effectively displays a peradectid-like outline shape for a m1, with a trigonid much longer than the talonid, the hypoconid mesiolabial to the entoconid, the convex distolingual margin of the talonid, and the lingual opening of the trigonid basin higher than the talonid one (see Table 6). MNHN.F.Gr10010 (L = 1.56 mm, W = 0.79 mm) is similar in size to
lower molars of *Pd. louisi* and *Pd. dufraingi*. However, this is not sufficient to propose a specific
allocation, in part because the m1 of the slightly smaller *Pd. dufraingi* is so far undocumented.

MNHN.F.GR10013 (Fig. 17b-c; L = 1.56 mm, W = 0.85 mm) was listed as a left m4 (Crochet
1980b). It is less worn than MNHN.F.GR10010, especially on the talonid. MNHN.F.GR10013
is more likely a m3, rather than a m2 or m4, given that its talonid is relatively not as wide as on
m2 of peradectids and also unreduced compared to m4 of peradectids (Fig. 17b). The lingual
margin of the talonid is less worn than the rest of the molar, and preserves a minute entoconid
smaller than the hypoconulid (Fig. 17c). Contrary to all m3 of *Pd. louisi*, the entoconid is lower
than the hypoconulid. This character is exclusively shared with *Pd. dufraingi*, from the Egem
locality (Smith and Smith 2013: fig. 4B-G). Because MNHN.F.GR10013 differs from m3 of
*Pd. dufraingi* only in being larger (but is as long and wide as m3 of *Pd. louisi*), and in its
stronger postcingulid (also similar to *Pd. louisi* in this respect), we here tentatively attribute this
peradectid m3 from Grauves to *Peradectes* aff. *dufraingi*. Regarding the exhibited features of
this material, *Pd. louisi* is hence clearly absent from Grauves. If the attribution we propose is
correct, and following the conclusion of Smith and Smith (2013: p. 308-309) on the age of the
Egem locality, MNHN.F.GR10013 would represent a species close to *Pd. dufraingi*, occurring
in the MP10 reference level (instead of ~MP8+9 for *Pd. dufraingi*), and a second peradectid
species with a minute entoconid recorded around the EECO.

*Peradectes louisi* was also recorded in Cuis (~MP10; = Grauves?, see Material and methods)
by Crochet (1980b: table 3), by an unlabeled right upper molar (Fig. 17a; L > 1.37 mm, W =
1.73 mm), the sole metatherian tooth from this locality, for which only a cast is available in the
fossil collections of the MNHN. The specimen is completely worn on its main cusps, stylar
cusps, and conules. The most distolabial part of the metastylar wing and stylar cusp A are
broken. Given the depth and asymmetry of the ectoflexus of this specimen, and the length of
the preparacrista, it is most likely a M2 as listed by Crochet (1980b). It is similar in size to both
<figure><img src="image_20.png" /></figure>

**Fig. 17** Revision and comparisons of peradectid molars from MP10 and ?MP10-11 faunas. **a-c.** molars from the MP10 faunas of Cuis and Grauves (Paris Basin) attributed to *Peradectes louisi* by Crochet (1980b). **a.** cast of an unlabelled right M2 from Cuis in occlusal view. **b-c.** MNHN.F.GR10013, left m3 here attributed to *Peradectes* aff. *dufraingi*; **b.** occlusal view; **c.** lingual view. The arrows (a and c) denote character states discussed in the main text. **d-g.** comparisons of outline of lingual views of m2 and m3 from the MP10 and ?MP10-11 faunas to those of typical m2 and m3 from MP8+9 and ~MP8+9 faunas of the Paris Basin. Note differences in the relative height and length of the entoconid; **d.** right m2 (reversed) MNHN.F.CB878 (*Pd. louisi*); **e.** left m3 MNHN.F.CB4213 (*Pd. louisi*); **f.** left m2 UM-VIE-106 (?*Pd. mutigniensis* in Legendre et al. 1992); **g.** left m3 MNHN.F.GR10013. Abbreviations: **pmc**, postmetacrista; **entoc**, entoconid. All outlines are to scale. Scale bar equals 1 mm.

upper molars of *Pd. louisi* and *Peradectes* sp. from Azillanet (Minervois, southern France, ~MP10), the latter being limited to one M3 (Marandat 1986: pl. 1, fig. 2). The unworn M3 from Azillanet differs from all upper molars of *Pd. louisi* in having a slightly V-shaped centrocrista (distinct from the V-shaped centrocrista of herpetotheriids), as in *Peradectes* specimens in open nomenclature from the ~MP10 southern France localities of Coulondres and Mas de Gimel (UM-CLR-1 and UM-MGL-716; Crochet 1980b: fig. 28; Vianey-Liaud et al. 2024: fig. 2C), and in its more curved and distally projected postmetacrista relatively to the paracone – metacone axis. On the M2 from Cuis, the centrocrista is completely worn and cannot be described, but the postmetacrista is curved and distally projected (Fig. 17a), in the same way as for the M3 from Azillanet. The M2 from Cuis sharing this character with the unnamed species
from Azillanet and being highly worn on all cusps, the presence of *Pd. louisi* in Cuis is here no
longer supported with confidence. Altogether, the revision of peradectids from Grauves and
Cuis shows that *Pd. louisi* is most likely absent from the MP10 and ~MP10 localities where it
was reported to date. The MP8+9-MP10 interval locality of Saint-Agnan yielded a possible *Pd.
louisi* specimen here described as *Peradectes* cf. *louisi*. The occurrences of *Pd. louisi* are hence
formally limited to MP8+9 and ~MP8+9 localities of the Paris Basin (Mutigny, Avenay, Condé-
en-Brie, Sables-de-Brasles, and Sézanne-Broyes).

A fragment of a peradectid m4 from Mas de Gimel (~MP10; Montpellier, France) was attributed to *Peradectes* cf. *mutigniensis* (UM-MGL-320; Vianey-Liaud et al. 2024: fig. 2D). Based on the morphology of the mesiolingual part of the trigonid (the only well-preserved part of the molar) and the apparently labiolingually pinched talonid, UM-MGL-320 is similar in size and morphology, only to the m4 of *Pd. russelli* (MNHN.F.Mu18003, Fig. 12u), and is thus tentatively re-attributed to *Peradectes* cf. *russelli*. A lower molar belonging to a peradectid was reported from the Vielase fauna (?MP10-11, Quercy) as ?*Peradectes mutigniensis* (Legendre et al. 1992). This specimen (UM-VIE-106; L = 1.73 mm, W = 0.99 mm) is a m2, given the relative width of the talonid. It is comparable in size to the largest m2 of *Pd. louisi* (e.g., MNHN.F.CB5092; Online Resource 1: Table S2) rather than the m2 of *Pd. russelli* (= *Pd. mutigniensis*'), which are larger. The entoconid and hypoconulid of UM-VIE-106 are small, identical in height and mesiodistal length (Fig. 17f), whereas the entoconid is most often higher and always mesiodistally longer than the hypoconulid on all m2 of the MP8+9 and ~MP8+9 European peradectids (e.g., Fig. 17d). The m2 from Vielase thus might belong to a different unnamed peradectid species. The comparison with *Peradectes* aff. *dufraingi* from Grauves is difficult because the cuspids of the talonid are described only for the m3 of this taxon.

Altogether, the peradectid m2 from Vielase and m3 from Grauves here revised, both of which
are late Ypresian in age, exhibit a configuration of the entoconid and hypoconulid that differs
from any peradectid molar of equivalent locus from the MP8+9 reference locality and ~MP8+9 localities of the Paris Basin, with a relatively less high entoconid (Fig. 17d-g). This may highlight a second species turnover among European peradectids, between middle early Eocene (MP8+9 or close in age) and late early Eocene (MP10 or close in age), although more dental material from MP10 and ~MP10 localities would be needed to update their tentative taxonomic status and confidently assess this hypothesis. To date, such low entoconids have been documented for *Peradectes dufraingi* (absent from the MP8+9 or localities close in age of the Paris Basin) from the Egem fauna, which would correlate with MP8+9 and the Early Eocene Climatic Optimum according to Smith and Smith (2013).

Peradectids are represented in southern France only in the MP7-MP8+9 interval localities that yielded *Pd. crocheti* sp. nov. and in MP10, ~MP10 and younger localities (Crochet 1977a, 1980b; Marandat 1986; Legendre et al. 1992). They are still unrecorded from southern France localities close in age to the MP8+9 of the Paris Basin, namely La Borie (= Saint-Papoul; Laurent et al. 2010) and Sainte-Eulalie (Danilo et al. 2013) probably due to the scarcity of small mammals in such localities. So far, only the ~MP8+9 locality of La Borie yielded an isolated lower molar of metatherian, belonging to a herpetotheriid (Crochet 1980b: p. 69).

## Conclusion

European peradectids long remained less well documented than both the coeval North American peradectids and the also superficially 'opossum-like' Herpetotheriidae, in terms of spatial distribution and completeness of available fossil material. The fossils described here for the early peradectid *Peradectes crocheti* sp. nov., widespread in Western Europe and being represented by dental rows, enhance our knowledge of the ancestral morphotype of European peradectids, through accurate comparisons with the later occurring species *Pd. louisi* and *Pd*.
russelli, and the tentative characterization of morphological intraspecific variation. We encourage further quantification of characters based on isolated molars, because it may enable to decipher cryptic diagnostic features between coeval metatherian species (e.g., Table 5) or to support evidenced species turnover (e.g., Fig. 14) for a given lineage (e.g., Fig. 15). In the same way, the study of the relative heights of the stylar cusps of metatherian upper molars also appears meaningful to resolve systematics, at least for peradectids (Fig. 5 vs Fig. 10 vs Fig. 12).

Altogether, the evolution of peradectids in Europe appears simpler than suggested by previous studies. In fact, the newly recorded species turnovers between the early (MP7-MP8+9 interval), middle (MP8+9 and ~MP8+9) and late (MP10 and ~MP10) early Eocene (Figs. 14, 17) must have resulted from the endemic evolution of a European lineage, originating from an unique dispersal from North America to Europe possibly triggered by the PETM, which is consistent with the monophyly of European peradectids (Fig. 16), rather than from a more complicated evolutionary history punctuated by multiple dispersals. In turn and although the precise relationships between the late Paleocene – middle Eocene peradectids are here established, their complex taxonomy at the generic level is to be addressed. These conclusions regarding the evolutionary history of peradectids are derived from the definition of multiple relevant dental characters for the first time, which provide support for many peradectid clades. Such effort will be crucial for understanding the origin and phylogenetic affinities of peradectids in the whole of Marsupialiformes.

To date, the last putative European peradectids are known by three complete specimens from Messel (~MP11, ~47.2 to ~47.6 Ma for the Middle Messel Formation; Kaboth-Bahr et al. 2024) preserving the skeleton, skull and teeth rows, but still of unclear taxonomic status (Kurz and Habersetzer 2004; Kurz 2007; Beck et al. 2022: p. 315). Furthermore, peradectids are known by only eight isolated teeth regarding MP10 and ~MP10, and ?MP10-11 localities (Crochet 1980b; Marandat 1986; Legendre et al. 1992), which represent the youngest ascertained record
of this family in Europe so far. For these reasons, the last steps of the evolution of peradectids
in Europe until their extinction, possibly after the MP11, remain blurry, awaiting for more fossil
material to be described. This work is a prelude of the complete systematic revision of
metatherians from the early Eocene of Europe.

**Supplementary informations** The online version contains supplementary material available at
https://doi.org/10.1007/s10914-024-09724-5.

**Acknowledgments** This article is dedicated to the memory of Jean-Yves Crochet, who passed away on 21 October 2023. As a long time colleague of the Institut des Sciences de l'Evolution – Montpellier (ISEM) and friend, he greatly improved our knowledge of metatherian and insectivorous mammals. We are indebted to the Rougier family, owner of the Palette site, who kindly provided access, help and support for paleontological research on this locality. We acknowledge Y. Dutour and N. Vialle (Muséum d'Histoire Naturelle of Aix-en-Provence), Q. Vautrin (Parc Naturel Régional UNESCO Global Geopark Causses du Quercy), C. Bronnert and R. Vacant (MNHN), and E. Turini and L. Mohring for their precious help during these excavations. R. Vacant also carefully treated the sediments from Palette collected in 2018, that yielded the holotype of *Peradectes crocheti* sp. nov. We warmly thank A.-L. Charruault (ISEM), who performed the µ-CT-scanning and segmentation of this holotype specimen. V.N. Pernègre (MNHN) managed the allocation of various new MNHN specimen numbers. G. Escarguel (LENHA, Lyon) sampled the locality of Fournes 2. We are grateful to T. Smith and A. Folie (Royal Belgian Institute of Natural Sciences, Brussels) for access to comparative material and casts of the two specimens from Sotteville-sur-Mer here revised. We thank V.D. Crespo and an anonymous reviewer, as well as the editors R.M.D. Beck and D.A Croft, for their constructive remarks on an early version of the manuscript. This is ISEM publication n° 2024-118.

**Author contributions** KG and RT designed the study. KG prepared the figures and wrote the manuscript, which was completed by comments and feedbacks from GB, EG, MG, BM, SL and RT. Field expeditions in the Palette locality were conducted by GB, EG and RT. The peradectid specimens
labelled MHN.AIX.PV.2017- were isolated by KG after processing sediments. Data acquisition (including CT-scans) and analyses were performed by KG. All authors read and approved the final manuscript.

**Funding** This research was financially supported by a PhD thesis funding from the French Ministry of Higher Education, Research, and Innovation, and also in part by the ANR project EDENs (ANR-20-CE02-0007). Recent excavations at Palette were funded thanks to the Actions Transversales du Muséum (ATM Palette, MNHN funding). Three-dimensional data acquisition was performed using the micro-computed tomography (μ-CT) facilities of the MRI platform member of the national infrastructure France-BioImaging supported by the French National Research Agency (ANR-10-INBS-04, ‘Investments for the future’), the labex CEMEB (ANR-10-LABX-0004) and NUMEV (ANR-10-LABX-0020). The Leica optical and digital station used to take photographs was acquired as part of the ANR-ERC PALASIAFRICA (ANR-08-JCJC-0017). A CC-BY public copyright license 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 grant’s open access conditions.

**Data availability** The 3D surface models of the most complete or informative specimens of *Peradectes crocheti* sp. nov. from Palette, namely the holotype (maxillary MHN.AIX.PV.2018.26.14), the P2 (MHN.AIX.PV.2017.6.6), a M3 (MHN.AIX.PV.2017.6.7), the two lower dental rows (MHN.AIX.PV.2017.6.8 and MHN.AIX.PV.2017.6.9), and the astragalus (MHN.AIX.PV.2017.6.14), are available on MorphoMuseum. The other 3D surfaces and data are available upon request to the corresponding author. The character – taxon matrix used in the first phylogenetic analysis is available in MorphoBank (project 5399).

**Competing interests** The authors declare no competing interests.

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**Supplementary material**

**Online resource 1** Additional measurement tables

**Online resource 2** Taxa used in phylogenetic analyses, with references and stratigraphic extensions

**Online resource 3** List of characters included in the phylogenetic analyses

**Online resource 4** Taxon-character matrix of the first phylogenetic analysis

**Online resource 5** Results and modifications made in the second and third phylogenetic analyses

**Online resource 6** Lingual (medial) view of the surface model of the right hemi-mandible fragment MHN.AIX.PV.2017.6.8
**Online Resource 1 Additional tables**

<table><caption>**Table S1.** Measurements of molars of *Peradectes crocheti* sp. nov. Abbreviations: L, length (mm); W, width (mm); L/W, length to width ratio.</caption><thead><tr><th>Specimen</th><th>Locality</th><th>Locus</th><th>L (mm)</th><th>W (mm)</th><th>L/W</th></tr></thead><tbody><tr><td>MHN.AIX.PV.2018.26.14</td><td>Palette</td><td>M1</td><td>1,55</td><td>1,59</td><td>0,97</td></tr><tr><td>MHN.AIX.PV.2018.26.20</td><td>Palette</td><td>M1</td><td>1,51</td><td>1,4</td><td>1,08</td></tr><tr><td>UM-FDN-1</td><td>Fordones</td><td>M1</td><td>1,64</td><td>1,57</td><td>1,04</td></tr><tr><td>UM-FNR2-1</td><td>Fournes</td><td>M1</td><td>1,71</td><td>1,41</td><td>1,21</td></tr><tr><td>MNHN.F.Me16079</td><td>Meudon</td><td>M1</td><td></td><td>1,41</td><td></td></tr><tr><td>MNHN.F.SN76</td><td>Soissons</td><td>M1</td><td>1,58</td><td>1,57</td><td>1,01</td></tr><tr><td>MHN.AIX.PV.2018.26.14</td><td>Palette</td><td>M2</td><td>1,5</td><td>1,7</td><td>0,88</td></tr><tr><td>NHMUK.PV.M44991</td><td>Abbey Wood</td><td>M2</td><td>1,57</td><td></td><td></td></tr><tr><td>NHMUK.PV.M66046</td><td>Croydon</td><td>M2</td><td>1,81</td><td>1,85</td><td>0,98</td></tr><tr><td>UM-FDN-21</td><td>Fordones</td><td>M2</td><td>1,5</td><td></td><td></td></tr><tr><td>UM-FDN-285</td><td>Fordones</td><td>M2</td><td>1,45</td><td></td><td></td></tr><tr><td>UM-FDN-287</td><td>Fordones</td><td>M2</td><td></td><td>1,66</td><td></td></tr><tr><td>UM-FNR2-2</td><td>Fournes</td><td>M2</td><td>1,58</td><td></td><td></td></tr><tr><td>MNHN.F.Me15975</td><td>Meudon</td><td>M2</td><td>1,56</td><td></td><td></td></tr><tr><td>MHN.AIX.PV.2017.6.7</td><td>Palette</td><td>M3</td><td>1,53</td><td>1,98</td><td>0,77</td></tr><tr><td>MHN.AIX.PV.2018.26.14</td><td>Palette</td><td>M3</td><td>1,4</td><td>1,77</td><td>0,79</td></tr><tr><td>UM-FDN-21</td><td>Fordones</td><td>M3</td><td></td><td>1,79</td><td></td></tr><tr><td>UM-FDN-23</td><td>Fordones</td><td>M3</td><td>1,53</td><td></td><td></td></tr><tr><td>MNHN.F.SN18</td><td>Soissons</td><td>M3</td><td>1,6</td><td>1,83</td><td>0,87</td></tr><tr><td>MNHN.F.SN78</td><td>Soissons</td><td>M3</td><td></td><td>1,79</td><td></td></tr><tr><td>Fig. 5.18 Smith et al. 2011</td><td>Sotteville-sur-Mer</td><td>M3</td><td>1,58</td><td>1,91</td><td>0,83</td></tr><tr><td>UM-FDN-286</td><td>Fordones</td><td>M4</td><td>1,12</td><td></td><td></td></tr><tr><td>MNHN.F.Me16084</td><td>Meudon</td><td>M4</td><td>1,26</td><td>1,79</td><td>0,70</td></tr><tr><td>MHN.AIX.PV.2017.6.9</td><td>Palette</td><td>m1</td><td>1,57</td><td>0,93</td><td>1,69</td></tr><tr><td>MNHN.F.Ri516</td><td>Rians</td><td>m1</td><td></td><td>0,94</td><td></td></tr><tr><td>MNHN.F.SN121</td><td>Soissons</td><td>m1</td><td>1,47</td><td>0,86</td><td>1,71</td></tr><tr><td>MHN.AIX.PV.2017.6.8</td><td>Palette</td><td>m2</td><td>1,65</td><td>1,04</td><td>1,59</td></tr><tr><td>MHN.AIX.PV.2017.6.9</td><td>Palette</td><td>m2</td><td>1,64</td><td>1,03</td><td>1,59</td></tr><tr><td>MNHN.F.Me16101</td><td>Meudon</td><td>m2</td><td>1,69</td><td>0,99</td><td>1,71</td></tr><tr><td>MNHN.F.Ri221</td><td>Rians</td><td>m2</td><td>1,69</td><td></td><td></td></tr><tr><td>MHN.AIX.PV.2017.6.8</td><td>Palette</td><td>m3</td><td>1,66</td><td>1,04</td><td>1,60</td></tr><tr><td>MHN.AIX.PV.2017.6.9</td><td>Palette</td><td>m3</td><td>1,68</td><td>1,06</td><td>1,58</td></tr><tr><td>MHN.AIX.PV.2017.6.10</td><td>Palette</td><td>m3</td><td>1,54</td><td>0,87</td><td>1,77</td></tr><tr><td>UM-PAT-103</td><td>Palette</td><td>m3</td><td>1,53</td><td>0,94</td><td>1,63</td></tr><tr><td>MNHN.F.SN2508</td><td>Soissons</td><td>m3</td><td>1,61</td><td>0,95</td><td>1,69</td></tr><tr><td>MHN.AIX.PV.2017.6.9</td><td>Palette</td><td>m4</td><td>1,55</td><td>0,92</td><td>1,68</td></tr></tbody></table>
<table><caption>**Table S2.** Detailed measurements of molars of *Peradectes louisi*. Abbreviations: L, length (mm); W, width (mm); L/W, length to width ratio; *, *Peradectes* cf. *louisi*.</caption><thead><tr><th>Specimen</th><th>Locality</th><th>Locus</th><th>L (mm)</th><th>W (mm)</th><th>L/W</th></tr></thead><tbody><tr><td>MNHN.F.Mu18005</td><td>Mutigny</td><td>dP3/</td><td>1,54</td><td>1,26</td><td>1,22</td></tr><tr><td>MNHN.F.Mu18006</td><td>Mutigny</td><td>M1</td><td>1,57</td><td>1,56</td><td>1,01</td></tr><tr><td>MNHN.F.Av16023</td><td>Avenay</td><td>M1</td><td>1,56</td><td>1,66</td><td>0,94</td></tr><tr><td>MNHN.F.Av16036</td><td>Avenay</td><td>M1</td><td>1,57</td><td>1,51</td><td>1,04</td></tr><tr><td>MNHN.F.Av16057</td><td>Avenay</td><td>M1</td><td>1,65</td><td>1,61</td><td>1,02</td></tr><tr><td>UM-AV-1-SK</td><td>Avenay</td><td>M1</td><td>1,49</td><td>1,55</td><td>0,96</td></tr><tr><td>UM-AV-2-SK</td><td>Avenay</td><td>M1</td><td>1,62</td><td>1,52</td><td>1,07</td></tr><tr><td>UM-AV-3-SK</td><td>Avenay</td><td>M1</td><td>1,62</td><td>1,6</td><td>1,01</td></tr><tr><td>MNHN.F.GL1</td><td>Sables de Brasles</td><td>M1</td><td>1,47</td><td>1,46</td><td>1,01</td></tr><tr><td>MNHN.F.GL296</td><td>Sables de Brasles</td><td>M1</td><td>1,53</td><td>1,45</td><td>1,06</td></tr><tr><td>MNHN.F.Mu6511</td><td>Mutigny</td><td>M2</td><td>1,62</td><td>1,86</td><td>0,87</td></tr><tr><td>MNHN.F.Av18003</td><td>Avenay</td><td>M2</td><td></td><td>1,78</td><td></td></tr><tr><td>MNHN.F.Av18004</td><td>Avenay</td><td>M2</td><td></td><td>1,87</td><td></td></tr><tr><td>MNHN.F.GL154</td><td>Sables de Brasles</td><td>M2</td><td></td><td>1,71</td><td></td></tr><tr><td>MNHN.F.GL272</td><td>Sables de Brasles</td><td>M2</td><td>1,56</td><td></td><td></td></tr><tr><td>MNHN.F.CB1486</td><td>Condé-en-Brie</td><td>M2</td><td></td><td>1,71</td><td></td></tr><tr><td>MNHN.F.CB3213</td><td>Condé-en-Brie</td><td>M2</td><td>1,52</td><td>1,77</td><td>0,86</td></tr><tr><td>MNHN.F.CB3228</td><td>Condé-en-Brie</td><td>M2</td><td>1,71</td><td>1,74</td><td>0,98</td></tr><tr><td>MNHN.F.CB3637</td><td>Condé-en-Brie</td><td>M2</td><td>1,65</td><td></td><td></td></tr><tr><td>MNHN.F.CB3707</td><td>Condé-en-Brie</td><td>M2</td><td>1,58</td><td>1,69</td><td>0,93</td></tr><tr><td>MNHN.F.CB4183</td><td>Condé-en-Brie</td><td>M2</td><td></td><td>1,83</td><td></td></tr><tr><td>MNHN.F.CB4182</td><td>Condé-en-Brie</td><td>M3</td><td>1,51</td><td>1,92</td><td>0,79</td></tr><tr><td>MNHN.F.GL197</td><td>Sables de Brasles</td><td>M3</td><td>1,63</td><td>1,85</td><td>0,88</td></tr><tr><td>MNHN.F.SZ18000</td><td>Sézanne-Broyes</td><td>M3</td><td>1,41</td><td>1,83</td><td>0,77</td></tr><tr><td>MNHN.F.SZ18005</td><td>Sézanne-Broyes</td><td>M3</td><td>1,47</td><td>1,72</td><td>0,85</td></tr><tr><td>MNHN.F.SZ18004</td><td>Sézanne-Broyes</td><td>M4</td><td>1,33</td><td>1,88</td><td>0,71</td></tr><tr><td>MNHN.F.Av16028</td><td>Avenay</td><td>m1</td><td>1,56</td><td>0,77</td><td>2,03</td></tr><tr><td>MNHN.F.Av7229</td><td>Avenay</td><td>m1</td><td>1,51</td><td>0,85</td><td>1,78</td></tr><tr><td>UM-AV-7-SK</td><td>Avenay</td><td>m1</td><td>1,45</td><td>0,76</td><td>1,91</td></tr><tr><td>UM-AV-12-SK</td><td>Avenay</td><td>m1</td><td>1,55</td><td>0,85</td><td>1,82</td></tr><tr><td>MNHN.F.CB962</td><td>Condé-en-Brie</td><td>m1</td><td>1,56</td><td>0,85</td><td>1,84</td></tr><tr><td>MNHN.F.CB4391</td><td>Condé-en-Brie</td><td>m1</td><td>1,52</td><td>0,83</td><td>1,83</td></tr><tr><td>MNHN.F.GL136</td><td>Sables de Brasles</td><td>m1</td><td>1,4</td><td>0,8</td><td>1,75</td></tr><tr><td>MNHN.F.SZ18003</td><td>Sézanne-Broyes</td><td>m1</td><td>1,43</td><td>0,78</td><td>1,83</td></tr><tr><td>MNHN.F.Av16016</td><td>Avenay</td><td>m2</td><td>1,54</td><td>0,9</td><td>1,71</td></tr><tr><td>MNHN.F.Av16027</td><td>Avenay</td><td>m2</td><td>1,64</td><td>0,94</td><td>1,74</td></tr></tbody></table>
<table>
  <tr>
    <td>MNHN.F.Av16044</td>
    <td>Avenay</td>
    <td>m2</td>
    <td>1,62</td>
    <td>0,89</td>
    <td>1,82</td>
  </tr>
  <tr>
    <td>MNHN.F.Av18001</td>
    <td>Avenay</td>
    <td>m2</td>
    <td>1,58</td>
    <td>0,98</td>
    <td>1,61</td>
  </tr>
  <tr>
    <td>MNHN.F.Av6830</td>
    <td>Avenay</td>
    <td>m2</td>
    <td>1,69</td>
    <td>1</td>
    <td>1,69</td>
  </tr>
  <tr>
    <td>UM-AV-10-SK</td>
    <td>Avenay</td>
    <td>m2</td>
    <td></td>
    <td>0,87</td>
    <td></td>
  </tr>
  <tr>
    <td>UM-AV-11-SK</td>
    <td>Avenay</td>
    <td>m2</td>
    <td>1,56</td>
    <td>0,9</td>
    <td>1,73</td>
  </tr>
  <tr>
    <td>MNHN.F.CB5090</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,7</td>
    <td>0,93</td>
    <td>1,83</td>
  </tr>
  <tr>
    <td>MNHN.F.CB5092</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,73</td>
    <td>0,99</td>
    <td>1,75</td>
  </tr>
  <tr>
    <td>MNHN.F.CB5097</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,67</td>
    <td>0,98</td>
    <td>1,70</td>
  </tr>
  <tr>
    <td>MNHN.F.CB828</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,66</td>
    <td>0,97</td>
    <td>1,71</td>
  </tr>
  <tr>
    <td>MNHN.F.CB872</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,69</td>
    <td>0,95</td>
    <td>1,78</td>
  </tr>
  <tr>
    <td>MNHN.F.CB878</td>
    <td>Condé-en-Brie</td>
    <td>m2</td>
    <td>1,72</td>
    <td>1</td>
    <td>1,72</td>
  </tr>
  <tr>
    <td>MNHN.F.SZ18001</td>
    <td>Sézanne-Broyes</td>
    <td>m2</td>
    <td>1,66</td>
    <td>0,92</td>
    <td>1,80</td>
  </tr>
  <tr>
    <td>MNHN.F.Av18000</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,63</td>
    <td>0,94</td>
    <td>1,73</td>
  </tr>
  <tr>
    <td>MNHN.F.Av18002</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,6</td>
    <td>0,95</td>
    <td>1,68</td>
  </tr>
  <tr>
    <td>MNHN.F.Av4642</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,47</td>
    <td></td>
    <td></td>
  </tr>
  <tr>
    <td>MNHN.F.AV16149</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,58</td>
    <td>0,85</td>
    <td>1,86</td>
  </tr>
  <tr>
    <td>MNHN.F.AV16158</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,61</td>
    <td>0,91</td>
    <td>1,77</td>
  </tr>
  <tr>
    <td>UM-AV-4-SK</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,51</td>
    <td>0,86</td>
    <td>1,76</td>
  </tr>
  <tr>
    <td>UM-AV-5-SK</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,51</td>
    <td>0,84</td>
    <td>1,80</td>
  </tr>
  <tr>
    <td>UM-AV-6-SK</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,54</td>
    <td>0,95</td>
    <td>1,62</td>
  </tr>
  <tr>
    <td>UM-AV-8-SK</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,56</td>
    <td>0,92</td>
    <td>1,70</td>
  </tr>
  <tr>
    <td>UM-AV-9-SK</td>
    <td>Avenay</td>
    <td>m3</td>
    <td>1,59</td>
    <td>0,88</td>
    <td>1,81</td>
  </tr>
  <tr>
    <td>MNHN.F.CB226</td>
    <td>Condé-en-Brie</td>
    <td>m3</td>
    <td>1,61</td>
    <td></td>
    <td></td>
  </tr>
  <tr>
    <td>MNHN.F.CB5104</td>
    <td>Condé-en-Brie</td>
    <td>m3</td>
    <td>1,6</td>
    <td>0,89</td>
    <td>1,80</td>
  </tr>
  <tr>
    <td>MNHN.F.CB959</td>
    <td>Condé-en-Brie</td>
    <td>m3</td>
    <td>1,62</td>
    <td>0,91</td>
    <td>1,78</td>
  </tr>
  <tr>
    <td>MNHN.F.CB4213</td>
    <td>Condé-en-Brie</td>
    <td>m3</td>
    <td>1,6</td>
    <td>0,92</td>
    <td>1,74</td>
  </tr>
  <tr>
    <td>MNHN.F.GL261</td>
    <td>Sables de Brasles</td>
    <td>m3</td>
    <td>1,54</td>
    <td>0,86</td>
    <td>1,79</td>
  </tr>
  <tr>
    <td>MNHN.F.GL263</td>
    <td>Sables de Brasles</td>
    <td>m3</td>
    <td>1,52</td>
    <td>0,86</td>
    <td>1,77</td>
  </tr>
  <tr>
    <td>MNHN.F.GL383</td>
    <td>Sables de Brasles</td>
    <td>m3</td>
    <td>1,66</td>
    <td>0,89</td>
    <td>1,87</td>
  </tr>
  <tr>
    <td>MNHN.F.SZ18006</td>
    <td>Sézanne-Broyes</td>
    <td>m3</td>
    <td>1,54</td>
    <td>0,87</td>
    <td>1,77</td>
  </tr>
  <tr>
    <td>MNHN.F.Av16032</td>
    <td>Avenay</td>
    <td>m4</td>
    <td>1,53</td>
    <td>0,85</td>
    <td>1,80</td>
  </tr>
  <tr>
    <td>MNHN.F.Av16037</td>
    <td>Avenay</td>
    <td>m4</td>
    <td>1,48</td>
    <td>0,85</td>
    <td>1,74</td>
  </tr>
  <tr>
    <td>MNHN.F.GL301</td>
    <td>Sables de Brasles</td>
    <td>m4</td>
    <td>1,44</td>
    <td>0,78</td>
    <td>1,85</td>
  </tr>
  <tr>
    <td>*MNHN.F.STA296</td>
    <td>Saint-Agnan</td>
    <td>m4</td>
    <td>1,5</td>
    <td>0,84</td>
    <td>1,79</td>
  </tr>
</table>
<table><caption>**Table S3.** Detailed measurements of molars of *Peradectes russelli*, with the original attribution of the specimens in Crochet (1980). Dash denote unpublished specimens. Abbreviations: L, length (mm); W, width (mm); L/W, length to width ratio.</caption><thead><tr><th>Specimen</th><th>Original attribution</th><th>Locality</th><th>Locus</th><th>L (mm)</th><th>W (mm)</th><th>L/W</th></tr></thead><tbody><tr><td>MNHN.F.Mu18004</td><td>Peradectes mutigniensis</td><td>Mutigny</td><td>M1</td><td>1,88</td><td>1,82</td><td>1,03</td></tr><tr><td>MNHN.F.Mu5532</td><td>-</td><td>Mutigny</td><td>M1</td><td>1,85</td><td>1,9</td><td>0,97</td></tr><tr><td>MNHN.F.Av16024</td><td>Peradectes mutigniensis</td><td>Avenay</td><td>M1</td><td>1,75</td><td>1,9</td><td>0,92</td></tr><tr><td>UM-AV-13-SK</td><td>-</td><td>Avenay</td><td>M1</td><td>1,73</td><td>1,78</td><td>0,97</td></tr><tr><td>MNHN.F.CB2501</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M1</td><td>1,97</td><td>2,09</td><td>0,94</td></tr><tr><td>MNHN.F.CB3007</td><td>Peradectes mutigniensis</td><td>Condé-en-Brie</td><td>M1</td><td>1,62</td><td>1,85</td><td>0,88</td></tr><tr><td>MNHN.F.CB3275</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M1</td><td>1,87</td><td>1,91</td><td>0,98</td></tr><tr><td>MNHN.F.Mu18002</td><td>Peradectes mutigniensis</td><td>Mutigny</td><td>M2</td><td>1,82</td><td>2,14</td><td>0,85</td></tr><tr><td>MNHN.F.CB5103</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M2</td><td>1,91</td><td>2,07</td><td>0,92</td></tr><tr><td>MNHN.F.CB840</td><td>-</td><td>Condé-en-Brie</td><td>M2</td><td>2,02</td><td>2,26</td><td>0,89</td></tr><tr><td>MNHN.F.CB850</td><td>-</td><td>Condé-en-Brie</td><td>M2</td><td>1,97</td><td>2,27</td><td>0,87</td></tr><tr><td>MNHN.F.CB2753</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M2</td><td>2,11</td><td></td><td></td></tr><tr><td>MNHN.F.Mu5521</td><td>Peradectes mutigniensis</td><td>Mutigny</td><td>M3</td><td>1,78</td><td>2,27</td><td>0,78</td></tr><tr><td>MNHN.F.Av4813</td><td>Peradectes russelli</td><td>Avenay</td><td>M3</td><td>1,95</td><td>2,27</td><td>0,86</td></tr><tr><td>MNHN.F.Av6837</td><td>Peradectes mutigniensis</td><td>Avenay</td><td>M3</td><td>1,82</td><td>2,29</td><td>0,79</td></tr><tr><td>MNHN.F.CB742</td><td>Peradectes mutigniensis</td><td>Condé-en-Brie</td><td>M3</td><td>1,95</td><td>2,4</td><td>0,81</td></tr><tr><td>MNHN.F.CB924</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M3</td><td>1,99</td><td>2,52</td><td>0,79</td></tr><tr><td>MNHN.F.CB2502</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M3</td><td>2,02</td><td>2,43</td><td>0,83</td></tr><tr><td>MNHN.F.CB924</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M4</td><td>1,35</td><td>2,36</td><td>0,57</td></tr><tr><td>MNHN.F.CB3021</td><td>Peradectes sp.</td><td>Condé-en-Brie</td><td>m1</td><td>1,71</td><td>0,89</td><td>1,92</td></tr><tr><td>MNHN.F.SZ18002</td><td>-</td><td>Sézanne-Broyes</td><td>m1</td><td>1,65</td><td>0,92</td><td>1,79</td></tr><tr><td>MNHN.F.Mu18000</td><td>Peradectes mutigniensis</td><td>Mutigny</td><td>m2</td><td>1,75</td><td>1,06</td><td>1,65</td></tr><tr><td>MNHN.F.Av7235</td><td>Peradectes russelli</td><td>Avenay</td><td>m2</td><td>1,98</td><td>1,17</td><td>1,69</td></tr><tr><td>UM-AV-14-SK</td><td>-</td><td>Avenay</td><td>m2</td><td>1,77</td><td>1,08</td><td>1,64</td></tr><tr><td>UM-AV-15-SK</td><td>-</td><td>Avenay</td><td>m2</td><td>1,97</td><td>1,19</td><td>1,66</td></tr><tr><td>MNHN.F.CB5098</td><td>Peradectes mutigniensis</td><td>Condé-en-Brie</td><td>m2</td><td>1,8</td><td>1,04</td><td>1,73</td></tr><tr><td>MNHN.F.CB5100</td><td>Peradectes mutigniensis</td><td>Condé-en-Brie</td><td>m2</td><td>1,94</td><td>1,13</td><td>1,72</td></tr><tr><td>MNHN.F.CB925</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>m2</td><td>2,03</td><td>1,25</td><td>1,62</td></tr><tr><td>MNHN.F.CB928</td><td>-</td><td>Condé-en-Brie</td><td>m2</td><td>2,05</td><td>1,22</td><td>1,68</td></tr><tr><td>MNHN.F.GL92</td><td>Peradectes mutigniensis</td><td>Sables de Brasles</td><td>m2</td><td>1,97</td><td>1,1</td><td>1,79</td></tr><tr><td>MNHN.F.Mu6451</td><td>Peradectes mutigniensis</td><td>Mutigny</td><td>m3</td><td>1,74</td><td>1,05</td><td>1,66</td></tr><tr><td>MNHN.F.GL410</td><td>-</td><td>Sables de Brasles</td><td>m3</td><td>1,85</td><td>1,11</td><td>1,67</td></tr><tr><td>MNHN.F.Mu18003</td><td>-</td><td>Mutigny</td><td>m4</td><td>1,75</td><td>1</td><td>1,75</td></tr></tbody></table>
<table><caption>**Table S4.** Absolute basal heights of stylar cusps C and D in *Peradectes crocheti* sp. nov., *Pd. louisi* and *Pd. russelli* (attributions from this study). Abbreviations: HC, absolute basal height of stylar cusp C (mm); HD, absolute basal height of stylar cusp D (mm); HC/HD, absolute basal height of stylar cusp C to absolute basal height of stylar cusp D ratio.</caption><thead><tr><th>Specimen</th><th>Species</th><th>Locality</th><th>Locus</th><th>HC (mm)</th><th>HD (mm)</th><th>HC/HD</th></tr></thead><tbody><tr><td>MHN.AIX.PV.2018.26.14</td><td>Peradectes crocheti</td><td>Palette</td><td>M1</td><td>0,03</td><td>0,039</td><td>0,769</td></tr><tr><td>MHN.AIX.PV.2018.26.20</td><td>Peradectes crocheti</td><td>Palette</td><td>M1</td><td>0,047</td><td>0,061</td><td>0,77</td></tr><tr><td>UM-FDN-1</td><td>Peradectes crocheti</td><td>Fordones</td><td>M1</td><td>0,083</td><td>0,107</td><td>0,776</td></tr><tr><td>UM-FNR2-1</td><td>Peradectes crocheti</td><td>Fournes</td><td>M1</td><td>0,057</td><td>0,09</td><td>0,633</td></tr><tr><td>MNHN.F.SN76</td><td>Peradectes crocheti</td><td>Soissons</td><td>M1</td><td>0,059</td><td>0,146</td><td>0,404</td></tr><tr><td>MHN.AIX.PV.2018.26.14</td><td>Peradectes crocheti</td><td>Palette</td><td>M2</td><td>0,036</td><td>0,074</td><td>0,486</td></tr><tr><td>NHMUK.PV.M44991</td><td>Peradectes crocheti</td><td>Abbey Wood</td><td>M2</td><td>0,058</td><td>0,064</td><td>0,906</td></tr><tr><td>NHMUK.PV.M66046</td><td>Peradectes crocheti</td><td>Croydon</td><td>M2</td><td>0,109</td><td>0,122</td><td>0,893</td></tr><tr><td>MNHN.F.Me15975</td><td>Peradectes crocheti</td><td>Meudon</td><td>M2</td><td>0,049</td><td>0,096</td><td>0,51</td></tr><tr><td>UM-FDN-285</td><td>Peradectes crocheti</td><td>Fordones</td><td>M2</td><td>0,046</td><td>0,06</td><td>0,767</td></tr><tr><td>UM-FDN-21</td><td>Peradectes crocheti</td><td>Fordones</td><td>M2</td><td>0,03</td><td>0,065</td><td>0,462</td></tr><tr><td>MHN.AIX.PV.2017.6.7</td><td>Peradectes crocheti</td><td>Palette</td><td>M3</td><td>0,086</td><td>0,063</td><td>1,365</td></tr><tr><td>MHN.AIX.PV.2018.26.14</td><td>Peradectes crocheti</td><td>Palette</td><td>M3</td><td>0,05</td><td>0,055</td><td>0,909</td></tr><tr><td>UM-FDN-21</td><td>Peradectes crocheti</td><td>Fordones</td><td>M3</td><td>0,073</td><td>0,055</td><td>1,327</td></tr><tr><td>UM-FDN-23</td><td>Peradectes crocheti</td><td>Fordones</td><td>M3</td><td>0,095</td><td>0,049</td><td>1,939</td></tr><tr><td>MNHN.F.SN18</td><td>Peradectes crocheti</td><td>Soissons</td><td>M3</td><td>0,103</td><td>0,111</td><td>0,928</td></tr><tr><td>MNHN.F.SN78</td><td>Peradectes crocheti</td><td>Soissons</td><td>M3</td><td>0,069</td><td>0,075</td><td>0,92</td></tr><tr><td>Fig. 5.18 Smith et al. 2011</td><td>Peradectes crocheti</td><td>Sotteville-sur-Mer</td><td>M3</td><td>0,131</td><td>0,104</td><td>1,26</td></tr><tr><td>MNHN.F.Mu18006</td><td>Peradectes louisi</td><td>Mutigny</td><td>M1</td><td>0,018</td><td>0,067</td><td>0,269</td></tr><tr><td>UM-AV-1-SK</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,024</td><td>0,057</td><td>0,421</td></tr><tr><td>UM-AV-2-SK</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,068</td><td>0,107</td><td>0,636</td></tr><tr><td>UM-AV-3-SK</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,062</td><td>0,083</td><td>0,747</td></tr><tr><td>MNHN.F.Av16023</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,033</td><td>0,063</td><td>0,524</td></tr><tr><td>MNHN.F.Av16036</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,047</td><td>0,062</td><td>0,758</td></tr><tr><td>MNHN.F.Av16057</td><td>Peradectes louisi</td><td>Avenay</td><td>M1</td><td>0,03</td><td>0,082</td><td>0,366</td></tr><tr><td>MNHN.F.GL1</td><td>Peradectes louisi</td><td>Sables de Brasles</td><td>M1</td><td>0,039</td><td>0,062</td><td>0,629</td></tr><tr><td>MNHN.F.GL296</td><td>Peradectes louisi</td><td>Sables de Brasles</td><td>M1</td><td>0,053</td><td>0,1</td><td>0,53</td></tr><tr><td>MNHN.F.Mu6511</td><td>Peradectes louisi</td><td>Mutigny</td><td>M2</td><td>0,053</td><td>0,127</td><td>0,417</td></tr><tr><td>MNHN.F.Av18003</td><td>Peradectes louisi</td><td>Avenay</td><td>M2</td><td>0,04</td><td>0,074</td><td>0,541</td></tr><tr><td>MNHN.F.Av18004</td><td>Peradectes louisi</td><td>Avenay</td><td>M2</td><td>0,029</td><td>0,053</td><td>0,547</td></tr><tr><td>MNHN.F.CB3213</td><td>Peradectes louisi</td><td>Condé-en-Brie</td><td>M2</td><td>0,038</td><td>0,041</td><td>0,927</td></tr><tr><td>MNHN.F.CB3228</td><td>Peradectes louisi</td><td>Condé-en-Brie</td><td>M2</td><td>0,048</td><td>0,042</td><td>1,143</td></tr></tbody></table>
<table><caption>**Table S5.** Measurements (in mm) of dentary height under m2 or m3 and results of dentary height to molar length ratios for *Peradectes crocheti* sp. nov., *Pd. louisi* and *Pd. russelli*. Abbreviations: Hm2, mandibular height below m2; Hm3, mandibular height below m3; Lm2, length of m2; Lm3, length of m3.</caption><tr><td>MNHN.F.GL154</td><td>Peradectes louisi</td><td>Sables de Brasles</td><td>M2</td><td>0,045</td><td>0,07</td><td>0,643</td></tr><tr><td>MNHN.F.GL272</td><td>Peradectes louisi</td><td>Sables de Brasles</td><td>M2</td><td>0,041</td><td>0,032</td><td>1,281</td></tr><tr><td>MNHN.F.Mu18001</td><td>Peradectes louisi</td><td>Mutigny</td><td>M3</td><td>0,019</td><td>0,051</td><td>0,373</td></tr><tr><td>MNHN.F.SZ18005</td><td>Peradectes louisi</td><td>Sézanne-Broyes</td><td>M3</td><td>0,044</td><td>0,04</td><td>1,1</td></tr><tr><td>MNHN.F.Mu18004</td><td>Peradectes russelli</td><td>Mutigny</td><td>M1</td><td>0,037</td><td>0,127</td><td>0,291</td></tr><tr><td>MNHN.F.Mu5532</td><td>Peradectes russelli</td><td>Mutigny</td><td>M1</td><td>0,061</td><td>0,114</td><td>0,535</td></tr><tr><td>MNHN.F.Av16024</td><td>Peradectes russelli</td><td>Avenay</td><td>M1</td><td>0,068</td><td>0,082</td><td>0,829</td></tr><tr><td>UM-AV-13-SK</td><td>Peradectes russelli</td><td>Avenay</td><td>M1</td><td>0,069</td><td>0,125</td><td>0,552</td></tr><tr><td>MNHN.F.CB2501</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M1</td><td>0,047</td><td>0,187</td><td>0,251</td></tr><tr><td>MNHN.F.CB3007</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M1</td><td>0,023</td><td>0,107</td><td>0,215</td></tr><tr><td>MNHN.F.CB3275</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M1</td><td>0,064</td><td>0,14</td><td>0,457</td></tr><tr><td>MNHN.F.Mu18002</td><td>Peradectes russelli</td><td>Mutigny</td><td>M2</td><td>0,097</td><td>0,12</td><td>0,808</td></tr><tr><td>MNHN.F.CB5103</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M2</td><td>0,067</td><td>0,12</td><td>0,558</td></tr><tr><td>MNHN.F.CB850</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M2</td><td>0,096</td><td>0,167</td><td>0,575</td></tr><tr><td>MNHN.F.CB2753</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M2</td><td>0,123</td><td>0,199</td><td>0,618</td></tr><tr><td>MNHN.F.Mu5521</td><td>Peradectes russelli</td><td>Mutigny</td><td>M3</td><td>0,044</td><td>0,087</td><td>0,506</td></tr><tr><td>MNHN.F.Av4813</td><td>Peradectes russelli</td><td>Avenay</td><td>M3</td><td>0,057</td><td>0,121</td><td>0,471</td></tr><tr><td>MNHN.F.Av6837</td><td>Peradectes russelli</td><td>Avenay</td><td>M3</td><td>0,073</td><td>0,182</td><td>0,401</td></tr><tr><td>MNHN.F.CB924</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M3</td><td>0,069</td><td>0,143</td><td>0,483</td></tr><tr><td>MNHN.F.CB2502</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M3</td><td>0,075</td><td>0,14</td><td>0,536</td></tr><tr><td>MNHN.F.CB742</td><td>Peradectes russelli</td><td>Condé-en-Brie</td><td>M3</td><td>0,033</td><td>0,141</td><td>0,234</td></tr></table>

<table><thead><tr><th>Specimen</th><th>Species</th><th>Hm2 (mm)</th><th>Hm3 (mm)</th><th>Hm2/Lm2</th><th>Hm3/Lm3</th></tr></thead><tbody><tr><td>MHN.AIX.PV.2017.6.8</td><td>Peradectes crocheti</td><td>2.71</td><td>2.73</td><td>1.64</td><td>1.64</td></tr><tr><td>MNHN.F.CB226</td><td>Peradectes louisi</td><td>2.99</td><td>3.01</td><td>-</td><td>1.87</td></tr><tr><td>MNHN.F.CB925</td><td>Peradectes russelli</td><td>3.53</td><td>-</td><td>1.74</td><td>-</td></tr></tbody></table>

**Supplementary reference for Table S3.**

Crochet JY (1980) Les marsupiaux du Tertiare d'Europe. Editions Foundation Singer-Polinac, Paris, France.
**Online Resource 2** List of taxa included in the phylogenetic analyses (with authorship and year), their systematic position, the specimens used for coding and references, and the stratigraphic extension of the species.

### Deltatheriidae Gregory and Simpson 1926

*Deltatheridium pretrituberculare* Gregory and Simpson 1926. Casts of ZPAL MGM-I/91 and ZPAL MGM-I/102 (University of Montpellier, France). Descriptions and illustrations from Kielan-Jaworowska (1975).

### Marsupialiformes Vullo et al. 2009; family *incertae sedis*

*Asiatherium reshetovi* Trofimov and Szalay 1994. Descriptions and illustrations from Szalay and Trofimov (1996).

### Peradectidae Crochet 1979

*Armintodelphys blacki* Krishtalka and Stucky, 1983a. Cast of CM 41159 (holotype) consulted (Royal Belgian Institute of Natural Sciences [RBINS], Brussels). Descriptions and illustrations from Krishtalka & Stucky (1983a, 1983b) and Smith and Smith (2013). From latest Wasatchian (Wa-7) to earliest Bridgerian (Br-0) (Krishtalka and Stucky 1983a; Korth 2008).

*Armintodelphys dawsoni* Krishtalka and Stucky, 1983a. Cast of CM 55569 (holotype) consulted (Royal Belgian Institute of Natural Sciences [RBINS], Brussels). Descriptions and illustrations from Krishtalka & Stucky (1983a, 1983b, 1984) and Smith and Smith (2013). Early Bridgerian (Br-0-Br-1) (Krishtalka and Stucky 1983a; Korth 2008).

*Armintodelphys dufraingi* Smith and Smith, 2013. Original specimens IRSNB M2152 (holotype) and IRSNB M2153 consulted (Royal Belgian Institute of Natural Sciences [RBINS], Brussels). Descriptions and illustrations from Smith and Smith (2013). Known from ~51-52 Ma (Egemkapel Clay Member; Smith and Smith 2013) to possibly MP10 reference level (this study).

*Mimoperadectes labrus* Bown and Rose 1979. Casts of UM 66144 (holotype, dental rows illustrated in pl. 1 and pl. 2, fig. 1 in Bown and Rose [1979]) and UM 113418 consulted (RBINS). Descriptions and illustrations from Bown and Rose (1979), Gingerich (1989), Strait (2001), Gingerich and Smith (2006) and Rose et al. (2012). Definitive *M. labrus* specimens are recorded in Wa-M and Wa-0 faunas (Bown and Rose 1979; Strait 2001; Gingerich and Smith 2006; Rose et al. 2012). The species maybe extends back to the latest Paleocene (Rose 1981: 36) and further into the early-middle Wasatchian, *Cantius trigonodus* zone (biochrons Wa-4-Wa-5) (Bown and Rose 1979: 96; Korth 2008: 716; Rose et al. 2012: 22).

*Peradectes californicus* (Stock 1936). Descriptions and illustrations from Stock (1936), Setoguchi (1975), Lillegraven (1976), Rothecker and Storer (1996) (fig. 1P interpreted as M2
instead of M3) and Murphey et al. (2018). From early Uintan (biochron Ui-1a, ~47 Ma) to late Duchesnean (biochron Du) (Murphey et al. 2018).

*Peradectes chesteri* (Gazin, 1952). Descriptions and illustrations from Gazin (1952), West (1973), Krishtalka and Stucky (1983a, 1983b, 1984) and Murphey et al. (2018). From late Wasatchian (biochron Wa-7) to early Uintan (biochron Ui-1b) (Murphey et al. 2018).

*Peradectes crocheti* sp. nov. All original material included in this study. Cast of the M3 from Sotteville-sur-Mer. Additional illustrations from Hooker (2010, 2020) for each Abbey Wood and Croydon specimen. Restricted to the [MP7-MP8+9 reference level] interval, with first occurrence just after the PETM (Smith et al. 2011) and last occurrences after the Eocene Thermal Maximum 2 (~biochron Wa5; Noiret et al. 2016).

*Peradectes elegans* Matthew and Granger, 1921. Casts of AMNH 17376 (holotype), 17383 and USNM 20879 (University of Montpellier, France). Descriptions and illustrations from Simpson (1928, 1935), Gazin (1956), McKenna (1960), Fox (1983) and Krishtalka and Stucky (1983b). We followed Williamson et al. (2012) in considering *Pd. pauli* as a junior synonym of *Pd. elegans*. Thus, specimens allocated to *Pd. pauli* (Krishtalka and Stucky 1983b), including USNM 20879, have been used for the coding of *Pd. elegans*. From early Tiffanian (biochron Ti-2 according to Korth 2008, biochron Ti-3 according to Secord 2008) to early Wasatchian (between biochrons Wa1-Wa3; McKenna 1960; Korth 2008).

*Peradectes gulottai* Rose 2010. Descriptions and illustrations from Rose (2010). Wasatchian in age (Rose 2010).

*Peradectes louisi* Crochet 1979. All original material included in the revision of *Pd. louisi* (this study). From (~)MP8+9 reference level (Mutigny; ~52-54 Ma; Neal 1996; Duprat 1997), to possibly [MP8+9-MP10] interval (this study).

*Peradectes protinnominatus* McKenna 1960. Casts of UCMP 44077 (holotype) and UCMP 45950 (University of Montpellier, France). Casts of UM 71663, UM 113305, UM 113391 and UM 113378 consulted at the Royal Belgian Institute of Natural Sciences (Brussels, Belgium). Descriptions and illustrations from McKenna (1960), Bown (1979), Rose (1981), Krishtalka and Stucky (1983b) and Gingerich and Smith (2006). Isolated molars of *Pd. protinnominatus* described by Strait (2001) are not included, because the only available illustration for this species is a herpetotheriid M3 (with a V-shaped centrocrista). From Clarkforkian (biochron Cf-2; Rose 1981) to early Wasatchian (biochron Wa-M to between biochrons Wa-1-Wa-3) (McKenna 1960; Gingerich and Smith 2006; Korth 2008).

*Peradectes russelli* Crochet 1979. All original material included in the revision of *Pd. russelli* (this study). From (~)MP8+9 reference level (Mutigny; ~52-54 Ma; Neal 1996; Duprat 1997), to possibly ~MP10 reference level (this study).

**Supplementary references for Online Resource 2**

Bown TM (1979) Geology and mammalian paleontology of the Sand Creek Facies, lower Willwood Formation (lower Eocene), Washakie County, Wyoming. Geological Survey of Wyoming Memoir 2: 1–151.
Bown TM, Rose KD (1979) *Mimoperadectes*, a new marsupial, and *Worlandia*, a new dermopteran, from the lower part of the Willwood Formation (early Eocene), Bighorn Basin, Wyoming. Contributions from the Museum of Paleontology, The University of Michigan 25: 89–104.

Crochet JY (1979) Diversité systématique des Didelphidae (Marsupialia) européens tertiaires. Géobios 12: 365-378.

Duprat M (1997) Les faciès à mammifères (MP 6 à MP 16) dans le Nord-Est du Bassin de Paris (France): argumentation du modèle tectono-sédimentaire des dépôts paléogènes. In: Aguilar JP, Legendre S, Michaux J (eds) Actes du Congrès BiochroM'97, Mémoires et travaux de l'EPHE 21. Ecole Pratique des Hautes Etudes, Institut de Montpellier, Montpellier, pp 315-336.

Gazin CL (1952) The lower Eocene knight formation of western Wyoming and its mammalian faunas. Smithsonian Miscellaneous Collections 117: 1-82.

Gazin CL (1956) Paleocene mammalian faunas of the Bison Basin in south-central Wyoming. Smithsonian Miscellaneous Collections 131: 1-57.

Gingerich PD (1989) New earliest Wasatchian mammalian fauna from the Eocene of northwestern Wyoming: composition and diversity in a rarely sampled high-floodplain assemblage. University of Michigan Papers on Paleontology 28: 1-97.

Gingerich PD, Smith T (2006) Paleocene-Eocene land mammals from three new latest Clarkforkian and earliest Wasatchian wash sites at Polecat Bench in the northern Bighorn Basin, Wyoming. Contributions from the Museum of Paleontology, University of Michigan 31: 245-303.

Gregory WK, Simpson GG (1926) Cretaceous Mammal Skulls from Mongolia. Nature 118: 698-699.

Hooker JJ (2010) The mammal fauna of the early Eocene Blackheath formation of Abbey Wood, London. Monographs of the Palaeontographical Society 164: 1-153.

Hooker JJ (2020) A mammal fauna from the Paleocene-Eocene Thermal Maximum of Croydon, London, UK. Proceedings of the Geologists' Association 131: 458-473.

Kielan-Jaworowska Z (1975) Evolution of the therian mammals in the Late Cretaceous of Asia. Part I. Deltatheridiidae. Palaeontologia Polonica 33: 103-132.

Korth WW (2008) Marsupialia. In: Janis CM, Gunnell GF, Uhen MD (eds) Evolution of Tertiary Mammals of North America: Volume 2, Small Mammals, Xenarthrans, and Marine Mammals. Cambridge University Press, Cambridge, pp 39-47.

Krishtalka L, Stucky RK (1983a) Revision of the Wind River faunas, early Eocene of Central Wyoming. Part 3. Marsupialia. Annals of Carnegie Museum 52: 205-227.

Krishtalka L, Stucky RK (1983b) Paleocene and Eocene marsupials of North America. Annals of Carnegie Museum 52: 229-263.

Krishtalka L, Stucky RK (1984) Middle Eocene marsupials (Mammalia) from northeastern Utah and the mammalian fauna from Powder Wash. Annals of Carnegie Museum 53: 31-45.

Lillegraven JA (1976) Didelphids (Marsupialia) and *Uintasorex* (?Primates) from later Eocene sediments of San Diego County, California. Transactions of the San Diego Society of Natural History 18: 85-112.

McKenna MC (1960) Fossil Mammalia from the early Wasatchian Four Mile fauna, Eocene of northwest Colorado. University of California Publications in Geological Sciences 37: 1-130.
Murphey P, Kelly T, Chamberlain K, Tsukui K, Clyde W (2018) Mammals from the earliest Uintan (middle Eocene) Turtle Bluff Member, Bridger Formation, southwestern Wyoming, USA, Part 3: Marsupialia and a reevaluation of the Bridgerian-Uintan North American Land Mammal Age transition. Palaeontologia Electronica 21(2):25A: 1–52.

Neal JE (1996) Summary of Paleogene sequence stratigraphy in northwest European and the North Sea. In: Knox RWOB, Corfield RM, Dunay RE (eds) Correlation of the Early Paleogene in Northwest Europe. Geol Soc London Spec Publ 101, pp 15–42.

Noiret C, Steurbaut E, Tabuce R, Marandat B, Schnyder J, Storme JY, Yans J (2016) New bio-
chemostratigraphic dating of a unique early Eocene sequence from southern Europe results in
precise mammalian biochronological tie-points. Newsletters on Stratigraphy 49: 469-480.

Rose KD (1981) The Clarkforkian Land-Mammal Age and mammalian faunal composition across the Paleocene-Eocene boundary. University of Michigan Papers on Paleontology 26: 1–197.

Rose KD (2010) New marsupial from the early Eocene of Virginia. Journal of Paleontology 84: 561–565.

Rose KD, Chew AE, Dunn RH, Kraus MJ, Fricke HC, Zack SP (2012) Earliest Eocene mammalian fauna from the Paleocene-Eocene Thermal Maximum at Sand Creek Divide, Southern Bighorn Basin, Wyoming. University of Michigan Papers on Paleontology 36: 1–122.

Rothecker J, Storer JE (1996) The marsupials of the Lac Pelletier lower fauna, Middle Eocene (Duchesnean) of Saskatchewan. Journal of Vertebrate Paleontology 16: 770–774.

Secord R (2008) The Tiffanian Land-Mammal Age (Middle and Late Paleocene) in the Northern Bighorn Basin, Wyoming. University of Michigan Papers on Paleontology 35: 1–192.

Setoguchi T (1975) Paleontology and geology of the Badwater Creek area, central Wyoming. Part 11. Late Eocene marsupials. Annals of Carnegie Museum 45: 263-275.

Simpson GG (1928) American Eocene didelphids. American Museum Novitates 307: 1–7.

Simpson GG (1935) The Tiffany fauna, Upper Paleocene. I.-Multituberculata, Marsupialia, Insectivora, and ?Chiroptera. American Museum Novitates 795: 1–19.

Smith T, Dupuis C, Folie A, Quesnel F, Storme J-Y, Iacumin P, Riveline J, Missiaen P, Ladevèze S, Yans J (2011) A new terrestrial vertebrate site just after the Paleocene–Eocene boundary in the Mortemer Formation of Upper Normandy, France. Comptes Rendus Palevol 10: 11–20.

Smith T, Smith R (2013) A land micro-mammal fauna from the Early Eocene marine Egem deposits (NP12, Belgium) and the first occurrence of the peradectid marsupial *Armintodelphys* outside North America. Geologica Belgica 16: 302–310.

Stock C (1936) Sespe Eocene Didelphids. Proceedings of the National Academy of Sciences 22: 122–124.

Strait SG (2001) New Wa-0 mammalian fauna from Castle Gardens in the southeastern Bighorn Basin. In: Gingerich, PD (ed) Paleocene-Eocene stratigraphy and biotic change in the Bighorn and Clarks Fork basins, Wyoming. University of Michigan Papers on Paleontology 33, pp. 127–143.

Szalay FS, Trofimov BA (1996) The Mongolian Late Cretaceous *Asiatherium*, and the early phylogeny and paleobiogeography of Metatheria. Journal of Vertebrate Paleontology 16: 474–509.
Trofimov BA, Szalay FS (1994) New Cretaceous marsupial from Mongolia and the early radiation of Metatheria. Proceedings of the National Academy of Sciences 91: 12569–12573.

Vullo R, Gheerbrant E, Muizon C de, Néraudeau D (2009) The oldest modern therian mammal from Europe and its bearing on stem marsupial paleobiogeography. Proceedings of the National Academy of Sciences 106: 19910–19915.

West RM (1973) Geology and mammalian paleontology of the New Fork-Big Sandy area, Sublette County, Wyoming. Fieldiana 29: 1–193.

Williamson TE, Brusatte SL, Carr TD, Weil A, Standhardt BR (2012) The phylogeny and evolution of Cretaceous–Palaeogene metatherians: cladistic analysis and description of new early Palaeocene specimens from the Nacimiento Formation, New Mexico. Journal of Systematic Palaeontology 10: 625–651.
**Online Resource 3** List of characters included in the cladistic analyses. It is mentioned if a dental character is taken or modified (change in the spelling and / or character states) from Williamson et al. (2014) or Muizon and Ladevèze (2022), or if it is 'new' [i.e. not mentioned in Williamson et al. (2014) or Muizon and Ladevèze (2022)]. For characters taking biometrics into account, the mean of the observed value for a given taxa was used to select the appropriate character state. States of characters newly introduced and informative for resolving relationships of peradectid species are illustrated (not to scale) when needed.

1. Distal heel on lower premolars [new]: at least one cuspid well-developed (0), small to undistinct (1).

<figure><img src="image_21.png" /><figcaption>**Figure S1.** States 0 and 1 for the character 1, illustrated on right p3 of *Peradectes crocheti* sp. nov. (0) and *Mimoperadectes labrus* (1). Drawing of *M. labrus* (reversed view) from Bown and Rose (1979).</figcaption></figure>

2. Diastema posterior to p1 [character 17 in Muizon and Ladevèze 2022]: present (0), absent (1).

3. Relative height of p3 [new]: higher than m1 (0), as high as m1 (1), lower than m1 (2).

4. m1 slightly shorter (< 10% shorter) than m2 [new]: absent (0), present (1).

5. Proportions of m2 or m3 [new]: length / width ratio < 1.75 (0), length / width ratio >= 1.75 (1).

6. m4 relative length [new]: shorter than m3 (0), as long as or longer than m3 (1).

7. Trigonid vs talonid width on m3 [modified from character 60 in Williamson et al. 2014; character 56 in Muizon and Ladevèze 2022]: trigonid wider than talonid (0), trigonid as wide as talonid (1).

8. Talonid length on m4 [new]: shorter than trigonid (0), as long as or longer than trigonid (1).

<figure><img src="image_22.png" /><figcaption>**Figure S2.** States 0 and 1 for the character 8, illustrated on left m4 of *Peradectes crocheti* sp. nov. (0) and *Armintodelphys blacki* (1). Picture of *Arm. blacki* modified from Smith and Smith (2013).</figcaption></figure>

9. Metaconid position on the anteroposterior axis of m2 or m3 [new]: metaconid almost directly lingual to protoconid (0), metaconid well distolingual to protoconid (1).
<figure><img src="image_23.png" /></figure>

**Figure S3.** States 0 and 1 for the character 9, illustrated on right m2 and right m3, respectively, of *Peradectes protinnominatus* (0) and *Peradectes louisi* (1). Picture of *Pd. protinnominatus* modified from Gingerich & Smith (2006).

10. Mesial end of cristid obliqua position on m2 or m3 [modified from character 80 in Williamson *et al.*, 2014; character 69 in Muizon & Ladevèze 2022]: ventral or lingual to protocristid notch (0), labial to protocristid notch (1).

11. Mesial end of cristid obliqua on m4 ventral to protocristid notch [modified from character 81 in Williamson *et al.* 2014]: absent (0), sometimes present (1).

12. Hypoflexid width [character 78 in Muizon & Ladevèze 2022]: deep (ca. 40-50% of talonid width) (0), shallow (less than 40% of talonid width) (1).

13. Emargination of the labial margin of m3 [new]: present (0), absent (1).

<figure><img src="image_24.png" /></figure>

**Figure S4.** States 0 and 1 for the character 13, illustrated on left m3 of *Peradectes louisi* (0) and *Peradectes crocheti* sp. nov. (1).

14. Angle (in degree of arc) between cristid obliqua and postcristid on m2 or m3 [new]: ca. 70° or more (0), ca. 65° or less (1).

15. Postcristid morphology on m2-m4 [new]: straight at least on one molar locus (0), curved (1).

<figure><img src="image_25.png" /></figure>

**Figure S5.** States 0 and 1 for the character 15, illustrated on left m2 of *Mimoperadectes labrus* (0) and *Peradectes crocheti* sp. nov. (1). Picture of *M. labrus* modified from Rose *et al.* (2012).

16. Postcingulid morphology on m1-m3 [new]: extends lingually towards the hypoconulid tip (0), attenuates labially to the hypoconulid (1).
<figure><img src="image_26.png" /></figure>

**Figure S6.** States 0 and 1 for the character 16, illustrated on left m3 and m2, respectively, of *Armintodelphys dawsoni* (0) and *Peradectes louisi* (1). Picture of *Arm. dawsoni* modified from Krishtalka and Stucky (1984).

17. Postcingulid on m4 [character 74 in Williamson et al. 2014; character 79 in Muizon and Ladevèze 2022]: present (0), absent (1).

18. Notch between entoconid and hypoconulid on m3 [new]: shallower than the metaconid – entoconid notch (0), almost as deep as the metaconid – entoconid notch (1).

<figure><img src="image_27.png" /></figure>

**Figure S7.** States 0 and 1 for the character 18, illustrated on right m3 of *Peradectes louisi* (0) and *Peradectes crocheti* sp. nov. (1).

19. Relative height of entoconid and hypoconulid [new]: hypoconulid lower than or equal in height to entoconid on all molars, or higher than entoconid only on m4 (0), hypoconulid higher than entoconid on m3 and m4 (1).

<figure><img src="image_28.png" /></figure>

**Figure S8.** States 0 and 1 for the character 19, illustrated on left (reversed view) and right, respectively, m3 and m4 of *Peradectes crocheti* sp. nov. (0) and ‘*Armintodelphys*’ *dufraingi* (1). Picture of ‘*Arm*.’ *dufraingi* modified from Smith and Smith (2013).

20. Pre-entocristid morphology [character 76 in Muizon and Ladevèze 2022]: absent or weakly developed (0), well-developed and sharp (1).

21. Entoconid apex position relative to trigonid on m2 and m3 [character 75 in Muizon and Ladevèze 2022]: closer to the distolingual corner of the tooth (posterior) (0), intermediate between distal edge of trigonid and distal margin of the tooth (anterior) (1).

22. Disparity of length (L) / width (W) ratio between M2 and M3 [new]: (M2 L/W – M3 L/W) > 0.10 (0), (M2 L/W – M3 L/W) <= 0.10 (1).
23. Talon size [modified from character 46 in Muizon and Ladevèze 2022]: mesiodistally narrow (0), mesiodistally expanded (1).

24. Protocone position [modified from character 51 in Williamson et al. 2014]: lingual to paracone (0), distolingual to paracone (1).

25. Protocone relative height on M1-M3 [modified from character 50 in Williamson et al. 2014]: lower than paracone and metacone (0), subequal or higher than paracone or metacone (1).

26. Conules wing-like (internal and external) cristae on M1-M3 [character 45 in Muizon and Ladevèze 2022]: absent (0), present (1).

27. Largest conule on M1-M3 [new]: paraconule larger or conules subequal in size (0), metaconule larger (1).

28. Relative height of paracone vs metacone on M1-M3 [modified from character 41 in Williamson et al. 2014; character 37 in Muizon and Ladevèze 2022]: slightly taller (0), slightly smaller (1).

29. Postmetacrista length on M2 or M3 [character 29 in Muizon and Ladevèze 2022]: subequal to or shorter than preparacrista (0), longer than preparacrista (1).

30. Distal margin morphology on M1-M3 [new]: rectilinear at least on one molar locus, or with a postmetaconular crista extending distolabially to the lingual extremity of the metacone base (0), emarginated between talon and stylar shelf (1).

<figure><img src="image_29.png" /></figure>

**Figure S9.** States 0 and 1 for the character 30, illustrated on M3 (reversed view for state 0) of *Peradectes louisi*. The arrow points the distal emargination.

31. Stylar cusp A most frequent position on M2 or M3 [new]: mesial to stylar cusp B (0), mesiolingual to stylar cusp B (1).

<figure><img src="image_30.png" /></figure>

**Figure S10.** States 0 and 1 for the character 31, illustrated on right M3 of *Peradectes protinnominatus* (0) and *Peradectes russelli* (1). Picture of *Pd. protinnominatus* modified from McKenna (1960).
32. Stylar cusp A relative size (length and width) on M3 [character 22 in Williamson et al. 2014]: subequal to or larger than stylar cusp B (0), distinctly smaller than stylar cusp B (1).

33. Stylar cusp B position on M1-M3 [modified from character 24 in Williamson et al. 2014]: mesiolabial to paracone apex (0), strictly labial to paracone apex at least on M1 and M2 (1).

34. Stylar cusp C on M2-M3 [modified from character 25 in Williamson et al. 2014; character 33 in Muizon and Ladevèze 2022]: absent (0), small (lower than st. B and st. D at least on one molar locus) (1), well-developed (as high as or higher than st. B or st. D) (2).

35. Stylar cusp D position on M1 [modified from character 32 in Williamson et al. 2014]: mesiolabial or strictly labial to metacone apex (0), distolabial to metacone apex (1).

36. M1 ectoflexus [new]: sometimes present (0), absent (1).

<figure><img src="image_31.png" /></figure>

**Figure S11.** States 0 and 1 for the character 36, illustrated on right M1 of *Peradectes russelli* (0) and *Peradectes crochetti* sp. nov. (1).

37. Ectoflexus symmetry [new]: present on M2 or M3, at least on one specimen (0), absent (1).

<figure><img src="image_32.png" /></figure>

**Figure S12.** States 0 and 1 for the character 37, illustrated on right M2 of *Peradectes chesteri* (0) and left M3 of *Peradectes crochetti* sp. nov. (1). Picture of *Pd. chesteri* (reversed view) modified from Krishtalka & Stucky (1984).

**Supplementary references (not present in Online Resource 2) for Online Resource 3**

Muizon C de, Ladevèze S (2022) New material of *Incadelphys antiquus* (Pucadelphyda, Metatheria, Mammalia) from the early Palaeocene of Bolivia reveals phylogenetic affinities with enigmatic North and South American metatherians. *Geodiversitas* 44:609-643.

Williamson TE, Brusatte SL, Wilson GP (2014) The origin and early evolution of metatherian mammals: the Cretaceous record. *ZooKeys* 465:1–76.
**Online Resource 4** Taxon-character matrix (14 taxa, 37 characters) of the first phylogenetic analysis. A dash denotes inapplicability. Brackets denote morphological polymorphism.

<table><tr><td>Deltatheridium pretrituberculare</td><td>001000001000000-10-000000000010000-00</td></tr><tr><td>Asiatherium reshetovi</td><td>0010010110100110000001111100101000001</td></tr><tr><td>Peradectes elegans</td><td>0(01)1001100101(01)0100(01)0100110111100002010</td></tr><tr><td>Peradectes protinnominatus</td><td>011100000101(01)0110101(01)00001111101(01)2000</td></tr><tr><td>Peradectes crocheti sp. nov.</td><td>01010010(01)10110110101110(01)01111(01)1112111</td></tr><tr><td>Peradectes russelli</td><td>??00100110100011001(01)10001111(01)1111101</td></tr><tr><td>Peradectes louisi</td><td>??11000111100(01)11001110001111(01)1111101</td></tr><tr><td>Armintodelphys dufraingi</td><td>???11001111000110111??????????????</td></tr><tr><td>Mimoperadectes labrus</td><td>11010100111(01)1001(01)01101(01)(01)1111000102100</td></tr><tr><td>Armintodelphys blacki</td><td>11??01111101101110110??????????????</td></tr><tr><td>Armintodelphys dawsoni</td><td>???011101011000?0110?0000?1000?02??0</td></tr><tr><td>Peradectes chesteri</td><td>??21(01)000(01)101111100?000000011011101100</td></tr><tr><td>Peradectes gulottai</td><td>??????????????????1001011111001??1</td></tr><tr><td>Peradectes californicus</td><td>1121110001011111101001001111111001101</td></tr></table>

**Online Resource 5** Modified spelling of characters or character states (modified parts are in bold), subsequent amendments in the scoring and results of the second and third phylogenetic analysis, replacing frequencies of observations by morphological polymorphism.

**Changes in the spelling and scoring, and result for the second phylogenetic analysis:**

11. Mesial end of cristid obliqua on m4 ventral to protocristid notch [modified from character 81 in Williamson et al. 2014]: absent (0), **present** (1).

31. **Stylar cusp A position** on M2 or M3 [new]: mesial to stylar cusp B (0), mesiolingual to stylar cusp B (1).

36. M1 ectoflexus [new]: **present** (0), absent (1).

Changes in the scoring of character **11. Peradectes louisi, Mimoperadectes labrus**: 1 -> 0&1

Changes in the scoring of character **31. Peradectes protinnominatus**: 0 -> 0&1; **Peradectes crocheti** sp. nov., **Peradectes louisi**, **Peradectes chesteri**, **Peradectes californicus**: 1 -> 0&1
Changes in the scoring of character 36. *Peradectes louisi*, *Peradectes russelli*: 0 -> 0&1

<figure><img src="image_33.png" /></figure>

**Figure S1** Ingroup from the single most-parsimonious tree obtained in the second analysis (111 steps, same topology as the first analysis; CI = 0.604, RI = 0.517; see main text for described changes in Bremer indices and non-ambiguous synapomorphies).

Additional changes (characters 11, 31 and 36 modified as in the second analysis) in the
spelling and scoring, and result for the third phylogenetic analysis:

37. Ectoflexus symmetry [new]: **present on M2 or M3** (0), absent (1).
'present on M2 or M3, **at least on one specimen**' (analysis 1 and 2) > 'present on M2 or M3'
(analysis 3).

Change in the scoring of character 37. *Peradectes chesteri*: 0 -> 0&1

<figure><img src="image_34.png" /></figure>

**Figure S2** Ingroup from the two most-parsimonious tree obtained in the third analysis, of 112 steps each (CI = 0.607, RI = 0.511). The non-ambiguous synapomorphies for taxa of main interest are figured at node or branch.
**Online resource 6** Lingual (medial) view of the surface model of the right hemi-mandible fragment MHN.AIX.PV.2017.6.8, *Peradectes crocheti* sp. nov. from Palette (Provence; MP7-MP8+9 interval).

<figure><img src="image_35.png" /></figure>