# Unexpected pampatheriid from the early Oligocene of Peruvian Amazonia: insights into the tropical differentiation of cingulate xenarthrans

François Pujos, Lionel Hautier, Pierre-Olivier Antoine, Myriam Boivin, Benoit

Moison, Rodolfo Salas- Gismondi, Julia V Tejada, Rafael M Varas-Malca,

Johan Yans, Laurent Marivaux

<figure><img src="image_1.png" /></figure>

► To cite this version:

François Pujos, Lionel Hautier, Pierre-Olivier Antoine, Myriam Boivin, Benoit Moison, et al.. Unexpected pampatheriid from the early Oligocene of Peruvian Amazonia: insights into the tropical differentiation of cingulate xenarthrans. Historical Biology, In press, 10.1080/08912963.2025.2481525. hal-05010393

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<figure><img src="image_2.png" /></figure>
Unexpected pampatheriid from the early Oligocene of Peruvian
Amazonia: insights into the tropical differentiation of cingulate
xenarthrans

François Pujos IDa,b, Lionel Hautier IDc, Pierre-Olivier Antoine IDc, Myriam Boivin Id,c,d,e, Benoit Moison Idc, Rodolfo Salas-Gismondi If,g, Julia V. Tejada Idh, Rafael M. Varas-Malca Idg, Johan Yans Idi, and Laurent Marivaux Idc

<footnote>a Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-UNCUYO-Mendoza, Av. Ruiz Leal s/n, Parque Gral. San Martín, 5500, Mendoza, Argentina;</footnote>

<footnote>b Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, Ciudad Autónoma de Buenos Aires, Argentina;</footnote>

<footnote>c Institut des Sciences de l'Évolution de Montpellier, Univ. Montpellier, CNRS, IRD, Place Eugène Bataillon, 34095, Montpellier, France;</footnote>

<footnote>d Grupo de Paleontología de Vertebrados, Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy (UNJu), CONICET, Av. Bolivia 1661, 4600, San Salvador de Jujuy 4600, Jujuy, Argentina;</footnote>

<footnote>e Instituto de Geología y Minería (IDGyM), Universidad Nacional de Jujuy, Av. Bolivia 1661, 4600, San Salvador de Jujuy, Argentina;</footnote>

<footnote>f BioGeoCiencias Lab, Laboratorios de Investigación y Desarrollo (LID), Facultad de Ciencias y Filosofía, Centro de Investigación para el Desarrollo Integral y Sostenible (CIDIS), Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Lima 30, Peru;</footnote>

<footnote>g Departamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Av. Arenales 1256, Lima 14, Peru;</footnote>

<footnote>h Division of Geological and Planetary Sciences, California Institute of Technology, CA 91125, Pasadena, United States; i Department of Geology, Institute of Life, Earth and Environment (ILEE), University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium.</footnote>
ABSTRACT

Cingulates (armoured xenarthrans) constitute one of the most peculiar endemic clades of South American mammals. Their first occurrence in the fossil record can be traced back to the early Eocene. However, their Palaeogene remains are scarce, especially in tropical regions. Here we report an isolated molariform tooth of xenarthran from the early Oligocene of Peruvian Amazonia. This tooth is small and bilobed, with slightly marked apicobasal sulci, more compatible with a cingulate dental pattern than that of folivorans (the only toothed pilosans). High-resolution microtomography of this specimen reveals an inner layer highly vascularised suggestive of osteodentine, encircled by a middle layer of orthodentine with densely S-curved dentinal tubules, and a thin outer layer. There is no clear evidence regarding the presence of cement, otherwise typically present in tree sloths. Although its external appearance cannot fully discard an assignment to a sloth, the microstructural pattern, such as well-developed osteodentine arranged in a row without ramifications, suggests that this tooth belongs to an early pampatheriid. The presence of Oligocene Pampatheriidae in Western Amazonia, previously suggested by isolated osteoderms, is substantiated by this dental remain, which underlines the importance of tropical areas for the differentiation of cingulate xenarthrans.

KEYWORDS

Peru; Palaeogene; Pampatheriidae; dentinal microstructure; µCT imaging; historical biogeography
INTRODUCTION

Xenarthra constitutes one of the most peculiar groups of endemic South American mammals. They include Folivora (modern tree sloths and extinct ground sloths), Vermilingua (anteaters), and Cingulata (armadillos and extinct glyptodonts and pampatheres). The latter, the armoured xenarthrans are considered the oldest representatives of this mammalian suborder with the early Eocene dasypodid armadillo *Riostegotherium yanei* from Brazil (Itaboraí locality, Bergqvist et al. 2004; Figure 1A). Cingulates are characterised primarily by the presence of a carapace composed of fixed and mobile osteoderms that cover the head, body, and tail, and are easily preserved as fossils. Most of our knowledge about the evolution of South American mammals, and especially xenarthrans, is based on austral localities (e.g., Gaudin and Croft 2015). However, recent discoveries at lower latitudes (Andes and Amazonia; e.g., Muizon et al. 2015; Antoine et al. 2016; Zurita et al. 2016) have significantly altered our understanding of their palaeogeographical and evolutionary history.

Regarding armoured xenarthrans, dated molecular phylogenies suggest that glyptodonts diverged from other cingulates no more than 35 million years ago (mya; i.e., late Eocene; Delsuc et al. 2016), in agreement with the oldest osteoderm assigned to this family, *Glyptatelus fractus* (Mustersan South American Land Mammal Age [SALMA], 38–37 Ma, early late Eocene of Chubut, Patagonia Argentina; Simpson 1948; Zurita et al. 2016; Speijer et al. 2020) (Figure 1A). Pampatheriidae, commonly considered as the most derived of the five cingulate families, consist of unusual glyptodontoids with a semi-articulated armour. *Scirrotherium*, the oldest undisputed pampatheriid, dates back to the Early Miocene (Santacrucian SALMA) of northwestern Venezuela (Rincón et al. 2014) (Figure 1A). More recently, an undetermined pampathere was unambiguously identified from the late Oligocene CTA-32 fossil bearing locality in Peruvian Amazonia on the basis of an isolated osteoderm fragment with a prominent central figure and a rugose aspect (Contamana, Deseadan SALMA; Salas-Gismondi et al. 2011; Antoine et al. 2016; Supplementary Figure 1).

In August 2015, during a field season in Peruvian Amazonia, one of us (L.M.) discovered a less than one-centimetre long molariform tooth (MUSM 3965), at the TAR-22 fossil-bearing locality, in the vicinity of Tarapoto (San Martín Department), near Shapaja (Figure 1). This ever-growing tooth is characteristic of the xenarthrans (i.e., absence of cementum and enamel and presence of a central column of vasodentine). Mammalian remains from the same locality document caviomorph rodents, such as *Eoincamys* and *Selvamys* (Boivin et al. 2018, 2019), panperissodactyls (notoungulates and a litoptern), a pyrothere, as well as a palaeothentoid marsupial (Antoine et al. 2021). The TAR-22 assemblage was assigned an earliest Oligocene age (Tinguirirican SALMA; Antoine et al. 2021; Figure 1C).
Xenarthran remains from TAR-22 comprise osteoderms referred to the dasypodid *Parastegosimpsonia peruana* (Supplementary Figure 2; Antoine et al. 2021: Fig. 4M) and the isolated MUSM 3965 tooth (Figure 1E–H; Antoine et al. 2021: Fig. 4O, P). The latter was initially considered to be a probable mylodontid ground sloth on the basis of its external appearance and observable structures (Figure 1F–G; Antoine et al. 2021; Tejada et al. 2024). In the sub-coeval Peruvian locality of Santa Rosa (~29 Mya, Peruvian Amazonia; Figure 1A), no sloth is recorded and *P. peruana* is associated with *Yuruatherium tropicalis*, an enigmatic cingulate with uncertain taxonomic affinities (Ciancio et al. 2013; Supplementary Figure 2). *Yuruatherium* was also found in Argentinian Patagonia with *Y. intortum* (Sedor et al. 2017). Another close relative is documented by a very small osteoderm fragment at Shapaja, ~30 meters above TAR-22 in the same section (cf. *Yuruatherium*, TAR-01 locality, Boivin et al. 2018; Antoine et al. 2021; Supplementary Figure 2).

Here, using a high-resolution microtomography (µCT) approach, we analyse for the first time in three dimensions (3D) the internal microstructures of dental hard tissues of representatives of both extant and extinct cingulates and sloths. This analysis, combined with a re-examination of Palaeogene cingulate osteoderms, allows refining the taxonomic affinities of the peculiar MUSM 3965 molariform tooth from the early Oligocene of the Peruvian Amazonia. This study provides new insights into the early diversification of armoured xenarthrans in tropical environments.

## MATERIAL AND METHODS

We analysed the internal microstructure of the hard tissues of the MUSM 3965 molariform tooth using high-resolution microtomography (µCT, voxel size 0.0088 mm) which was performed at the MRI platform housed in the *Institut des Sciences de l'Évolution de Montpellier* (ISE-M). The microstructure was compared with that of five extant (tree-sloths *Bradypus* and *Choloepus*; armadillos *Dasypus*, *Tolypeutes*, and *Euphractus*) and two extinct (Late Pleistocene giant ground sloth *Megatherium* and *pampathere Holmesina*) xenarthran genera from the *Université de Montpellier* collection (Figures 2, 3; Supplementary Figure 1). Image segmentation of the microstructural patterns of the teeth was performed on the µCT images using Avizo.Lite 2019.4 software (Visualization Sciences Group). The virtually restored 3D models are deposited in MorphoMuseuM (Pujos et al. in press).

### Institutional abbreviation

MUSM: Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos, Lima, Peru.
Xenarthra Cope, 1889

Cingulata Illiger, 1811

Pampatheriidae Paula Couto 1954

Genus and species undetermined

### Specimen

MUSM 3965, molariform tooth (Figures 1F-H, 3).

### Locality and age

The specimen was collected at the TAR-22 fossil-bearing locality, situated in the western section of the Shapaja stratigraphic sequence, just above the confluence of the Huallaga and Mayo rivers (Figure 1B-C) in the San Martín Department of Peru (6°34′932″ S, 76°16′913″ W) (Antoine et al. 2021). The tooth, collected *in situ* within a roadside outcrop (Figure 1D-E), originates from lower Oligocene deposits of the Pozo Formation. The earliest Oligocene age (i.e., Tinguirirican SALMA; Figure 1C) was primarily assigned using chemostratigraphy on carbone isotope (δ¹³C on dispersed organic matter and paedogenic carbonate nodules; Yans in Antoine et al. 2021).

### Description

#### External aspect

Because mylodontid ground sloths exhibit bilobed molariform teeth, the specimen MUSM 3965 from TAR-22 was initially assigned to this family, and left in open nomenclature (“Mylodontidae indet.”; Antoine et al. 2021). However, MUSM 3965 is remarkably small (6.6 by 4.5mm) and it may be more consistent with cingulate than with ground-sloth affinities. Furthermore, the labial and lingual apicobasal sulci are slightly prominent, in contrast to the molariform teeth of late Oligocene Mylodontidae. The occlusal pattern of MUSM 3965 is similar to the characteristic bilobed molariform teeth of the Laventan species *Scirrotherium hondaense* from La Venta (13.8–11.8 Mya, Colombia; Edmund and Theodor 1997), which are the oldest known pampatheriid teeth published to date, and is clearly distinct from the trilobed teeth of the Glyptodontidae (e.g., Zurita et al. 2016).

#### Internal structure

For extant xenarthran species, our three-dimensional (3D) reconstructions mostly agree with the microstructural patterns previously described by Kalthoff (2011) based on histology two-dimensional (2D) scanning electron microscopy thin sections. The two modern tree sloth genera are characterised by a three-layer organisation of their dental microstructure, which consists of an inner layer of vasodentine, a middle layer of
orthodentine, and an outer layer of cementum (Figure 2A; Antoine et al. 2021; Supplementary Figure 1). However, the proportions of these layers differ between *Bradypus* and *Choloepus*, with the middle layer being thicker and the outer layer being much thinner in the former (Supplementary Figure 1). In both tree sloth genera, the inner layer of vasodentine is circular in shape and highly vascularised, with the diameter of the vascular canals being relatively large, averaging 10–20µm (Figure 2B). The canals are straight and radiate dorsally from the centre of the tooth (Figure 2C; Supplementary Figure 1). The microstructure of the bilophodont molariform in the extinct *Megatherium* is similar to extant folivorans and composed of the same three layers. However, the middle layer of orthodentine is thinner than in *Bradypus* and forms a morphological elevation in comparison to the inner layer of soft vasodentine, which is concave and represents a low morphological structure (depression) on the occlusal surface of the tooth (Figure 2D). The cementum in *Megatherium* is particularly thick and contains elongated canaliculi particularly dense at the cementum-dentine junction. These canaliculi are almost perpendicular to the main length of the orthodentine layer in occlusal view; they run almost parallel to the occlusal surface and are slightly ventrally oriented in lateral view (Figure 2E–F). The canaliculi are several hundred micrometres (µm) wide and as such much thicker than the vascular canals of the vasodentine.

Following Kalthoff (2011), the modern armadillo *Dasypus* displays a very similar microstructural organisation to that of extant sloths. Although the presence of an outer cementum layer could be clearly identified based on µCT images (Figure 2C), the junction between the middle and inner layers was subtler even if the core of the tooth was undoubtedly vascularised (Supplementary Figure 1). The two other armadillo genera, *Tolypeutes* (Figure 2G) and *Euphractus* (Supplementary Figure 1), are characterised by a simpler dental microstructure, mainly composed of orthodentine. The inner layer is somewhat scarred in appearance; it was then attributed to a degenerated osteodentine by Kalthoff (2011) as it resembles the osteodentine of extinct cingulates. The cementum is absent in both taxa, but a harder outermost rim in *Euphractus* might be constituted of hard orthodentine.

In contrast, the extinct pampatheriid *Holmesina* displays a fully developed osteodentine inner layer, with thick vascular canals (between 60 and 90 µm), lined up in a few rows that almost cross the entire occlusal surface (Figure 2I). This inner layer seems more resistant (higher) than its surrounding orthodentine layer, but less than the outermost rim of hardened orthodentine. The latter is clearly visible in occlusal view and cross-sections, and forms a prominent peripheral ridge (Figure 2I). The dentinal tubules of the orthodentine are barely distinguishable towards the apex of the crown; they cannot be mistaken with canals of vasodentine or osteodentine, their diameter being much smaller (Figure 2J–K).

The MUSM 3965 tooth displays a damaged occlusal surface (Figure 1F–G) and is constituted of three layers: a thin inner layer, a thick middle layer, and a thin outer layer
(Figure 3A). The inner layer is thin, line-shaped, and lacks ramifications (Figure 3B-C). It is highly vascularised and displays numerous canals for blood vessels and nerves that are perfectly lined in a row oriented antero-posteriorly (Figure 3B-C). The conformation and size (between 50 and 65 µm) of the canals are suggestive of osteodentine, although no osteon was unambiguously recognised. This inner layer forms a morphological relief (Figure 3C). The presence of interrupted posteriormost canals towards the apex of the tooth indicates that the apparent step-like relief of the occlusal surface is due to damage (Figure 3C). The thick middle layer is made of orthodentine, with clear densely-packed dentinal tubules in cross sections, which are slightly S-curved and rise radially toward the crown apex (Figure 3C). An outer layer, which forms a faded peripheral ridge, appears slightly harder than the bulk of the tooth. There is no clear evidence of the presence of cement, while a clear-cut junction between orthodentine and cement was always identified in *Bradypus*, *Choloepus*, and *Dasypus* (Figure 2A, C; Supplementary Figure 2).

DISCUSSION AND CONCLUSIONS

Teeth microstructure and hard tissues in xenarthrans

Kalthoff (2011) demonstrated the difficulties of using dentinal microstructure in a
phylogenetic context. However, some trends can be observed between the different
xenarthran orders and families (Figure 2; Supplementary Figure 1). The microstructural
pattern of the TAR-22 tooth (Figure 3) strongly resembles that of cingulates due to the
presence of osteodentine, absence of vasodentine, and strong presence of orthodentine,
particularly observed in extinct members such as pampatheres, glyptodonts, and
armadillos (i.e., *Proeutatus* and *Eutatus*) (Kalthoff 2011; this work). Orthodentine
constitutes the main dentinal component of the MUSM 3965 molariform tooth from
Tarapoto, but it also presents a characteristic association of a line-shaped osteodentine
and an outermost rim of hardened orthodentine (Figure 3A). In that sense, it clearly
departs from the three-layered microstructure of folivoran teeth composed of
vasodentine, orthodentine, and cementum (e.g., *Bradypus*, Figure 2A). Because
molariforms of the middle Eocene armadillo *Utaetus*, first described in Gran Barranca,
Patagonia (late Casamayoran SALMA, Ciancio et al. 2016), are characterised only by
orthodentine, a thin external layer of enamel, and lacks osteodentine Kalthoff (2011),
the absence of osteodentine is considered as the ancestral state of armoured
xenarthrans. In *Proeutatus* and *Eutatus*, the osteodentine presents a cloud-shaped area
in the centre of the tooth (Kalthoff 2011), which somewhat recalls the shape and
location of the so-called "degenerated" osteodentine of extant armadillos. MUSM 3965
presents fully-developed osteodentine lined in a row (Figure 3), as pampatheriids and
glyptodontids. However, unlike the latter, its inner layer of osteodentine does not show
any ramification. The late Oligocene (Deseadan SALMA) basal mylodontid
*Octodontotherium* is also characterised by a large amount of orthodentine, the absence of cementum, and the presence a small layer of vascularised dentine in the core of its teeth (Kalthoff 2011, but see Pujos et al. 2021). However, this inner layer corresponds to vasodentine (smaller canals than osteodentine and softer material; see Pujos et al. 2021), is cloud-shaped and more densely vascularised than the core of the MUSM 3965 tooth. The internal structure of this specimen discovered in the TAR-22 locality indicates that it does not correspond to a sloth but rather to a cingulate, with more affinities to pampatheriids than to glyptodontids and dasypodids.

## Palaeogene intertropical pampatheres and the early diversification of armoured xenarthrans

The remains of Palaeogene cingulates are primarily composed of isolated and fragmented osteoderms, which greatly complicates our understanding of the origin and evolutionary history of this group inasmuch as osteoderms are of limited phylogenetic insight (e.g., Billet et al. 2011; Barasoain et al. 2024). Based on the available fossil record, armadillos began to diversify by middle late Eocene times at southern latitudes (e.g., Ciancio et al. 2016). Only two glyptodontid genera are recognised during the Eocene, the glyptateline *Glyptatelus* and the palaeopeltine *Palaeopeltis*. During the late Eocene–Oligocene interval, glyptodontids were primarily found in southern South America, especially Argentina, before their diversification from the Neogene to the Quaternary (Zurita et al. 2016). Nevertheless, Palaeogene cingulates are also documented in Bolivia (Salla, late Oligocene; Shockey and Anaya 2008), Chile (Tinguiririca, early Oligocene; Croft et al. 2008), Peru (Contamana; late Eocene–late Oligocene; Shapaja, latest Eocene–early Oligocene; Santa Rosa, early Oligocene; e.g., Antoine et al. 2021), and Uruguay (Fray Bentos, late Oligocene; Reguero et al. 2003) (Figure 1A). Palaeogene armadillos, such as the euphractine *Parutaetus* and the eutatine *Meteutatus*, are commonly recognised in Argentina and Chile (Carlini et al. 2009).

Notably due to their elusive record, low-latitude Palaeogene xenarthrans have uncertain phylogenetic affinities, as illustrated by the early Oligocene Santa Rosa assemblage, with both *Yuruatherium tropicalis* and *Parastegosimpsonia peruana* (Ciancio et al. 2013; Supplementary Figure 2). *Par. peruana* occurs in latest Eocene–early Oligocene localities of the Shapaja section (TAR-21 and TAR-22, Figure 1C; Supplementary Figure 2). Interestingly, it was found alongside the MUSM 3965 pampatheriid molariform tooth at TAR-22.

The affinities of *Yuruatherium* remain controversial but Ciancio et al. (2013) have included *Machlydotherium intortum* in this genus (see Ciancio et al. 2013 for further information). As noted by its author, Ameghino (1902), and recently confirmed by Goís et al. (2013), *Machlydotherium* (from the middle-late Eocene of Patagonia) is likely closely related to Pampatheriidae, as indicated by the presence of bilobated molariform
teeth, which is a synapomorphy of the family. Furthermore, the isolated osteoderms of *Yuruatherium* (= *Machlydotherium*) are characterised by their great size, rough surface texture with large perforations, deep sulci between figures, typically featuring a prominent central figure, and imperfect union between them (Ciancio et al. 2013; Supplementary Figure 2). While these features are uncommon in armadillos, this general pattern is reminiscent of certain glyptodontoids and especially pampatheriids. We thus agree with Ameghino's original hypothesis that "*Machlydotherium*" is closely related to the Pampatheriidae (Ameghino 1902).

The TAR-22 and Santa Rosa faunas yielded the rodent *Eoincamys* and a similar cingulate assemblage, and they are relatively close geographically (Figure 1A). The occurrence of pampatheres in two early Oligocene localities (Santa Rosa and TAR-22) in the intertropical zone (Figure 1A) provides new insights into the early diversification and historical biogeography of cingulates. Thus far, other Palaeogene pampatheres were only recognised by an incomplete osteoderm from the late Oligocene CTA-32 locality (Antoine et al. 2016: Fig. 8F; Supplementary Figure 2). Neogene pampatheres are relatively well diversified, with four genera commonly accepted: *Plaina*, *Vassalia*, *Kraglievichia*, and *Scirrotherium* (Goís 2013). The latter genus is particularly abundant and widespread in northwestern South America (Colombia and Venezuela) from the late Early Miocene to Late Pliocene, with a dispersal into Central America during the Late Miocene (e.g., Costa Rica) prior to the Great American Biotic Interchange (GABI) (Jiménez-Lara 2020). The oldest pampatheriids were long known from the late Early Miocene of Patagonia, but we suggest here that this family would have a continuous Oligocene record at low latitudes (i.e., Santa Rosa, TAR-22, and CTA-32 localities, Peru). In addition, the La Venta fauna in Colombia (Carrillo et al. 2023) and the Fitzcarrald fauna in Peru (Tejada-Lara et al. 2015), both dating from the late Middle Miocene, show an unusually high diversity of xenarthrans, cingulates and ground sloths, which is almost unique for this epoch in South America.

The access to the internal microstructure in 3D of the hard tissues of the MUSM 3965 via high-resolution µCT imaging allows identifying this earliest Oligocene isolated dental specimen from TAR-22 as belonging to the Pampatheriidae. However, it is impossible to assign this isolated tooth to a specific genus or to determine its affinities with *Yuruatherium*. The Eocene/Oligocene transition (EOT) corresponds to a significant global cooling event that affected paleobiodiversity in South America (e.g., Coxall and Pearson 2007), possibly promoting extinctions, but also the emergence of new mammalian clades in South America, such as Pampatheriidae, as well as sloths and the peculiar genus *Pseudoglyptodon*, considered to be the sister genus of sloths (e.g., Casali et al. 2022, but see Tejada et al. 2024). The long history of Xenarthra, nearly 50 Ma, demonstrates the ability of its representatives to withstand significant climatic and environmental changes, as well as the arrival of immigrants during events such as GABI (e.g., Pujos et al. 2017). Xenarthrans may have taken advantage of the global climatic
deterioration from the late Eocene to the early Oligocene. During this interval, we
observe the diversification of armadillos and the appearance of glyptodonts,
pampatheriids, the *Pseudoglyptodon* lineage, and possibly ground sloths, while in
parallel, the diversity of other large herbivorous mammals, such as notoungulates,
decreases (e.g., extinction of Didolodontidae at the EOT, Croft et al. 2020). The presence
of the three oldest remains of Pampatheriidae in Peruvian Amazonia suggests a tropical
differentiation for this group and, contrary to what is commonly accepted (e.g., Gaudin
and Croft 2015), reinforces the importance of the South American tropics in the origin of
major clades of cingulates and the emergence of Xenarthra.

Acknowledgments

We are particularly indebted to M. Ciancio for providing the pictures of *Yuruatherium tropicalis*.

Disclosure statement

We declare we have no competing interests.

Funding

This study is part of the ongoing EMERGENCE strategic project of the LabEx CEBA (*Centre d'Étude de la Biodiversité Amazonienne; ANR-10-LABX-25-01*). Fieldwork and labwork were supported by the LabEx CEBA, the Leakey Foundation, the National Geographic Society, and the *Institut des Sciences de l'Évolution de Montpellier (ISE-M)*. Palaeontological investigations in Peruvian Amazonia are carried out in the framework of an ongoing collaboration agreement between the *Museo de Historia Natural de la Universidad Nacional Mayor San Marcos* (Lima, Peru) and the *Institut des Sciences de l'Évolution de Montpellier-Université de Montpellier, France*. This is ISE-M publication 2025-054 Sud.

ORCID

François Pujos ID http://orcid.org/0000-002-6267-3927

Lionel Hautier ID http://orcid.org/0000-0001-8701-5421

Pierre-Olivier Antoine ID http://orcid.org/0000-0001-9122-1818

Myriam Boivin ID http://orcid.org/0000-0002-5240-9460

Benoit Moison ID http://orcid.org/0009-0003-8019-7607

Rodolfo Salas-Gismondi ID http://orcid.org/0000-0001-9990-8841

Julia V. Tejada ID http://orcid.org/0000-0003-2307-6764

Rafael M. Varas-Malca ID http://orcid.org/0000-0002-4435-8229

Johan Yans ID http://orcid.org/0000-0001-7590-0298

Laurent Marivaux ID http://orcid.org/0000-0002-2882-0874
## Data accessibility

All data are included herein or in the Supplementary Figures 1 and 2 or in Pujos *et al*. (in press).

## Author's contributions

L.H. and F.P. designed and performed research and wrote the manuscript, J.Y. conducted the chemostratigraphy analyses, and B.M. generated most of the 3D models; L.M. and P.-O.A. have acquired funding for fieldwork and analyses; L.M., M.B., J.V.T.-L., R.S.-G., R.M.V.M., J.Y., P.-O.A., and F.P. performed fieldwork. All authors reviewed the manuscript and provided edits; they have given their final approval for publication and agreed to be held accountable for the work performed in this study.

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<figure><img src="image_3.png" /><figcaption>**Figure 1.** A, a hypothetical reconstruction of South America at Eocene/Oligocene boundary (34 Mya, based on Boschman 2021) and the location of the most important Paleogene and early Neogene fossil-bearing localities where cingulates are recorded. B, location of TAR-22 early Oligocene locality on the Huallaga River, Northern Peru, close to the Tarapoto city. C, synthetic stratigraphic sequence of the Shapaja Palaeogene section including the TAR-22 locality, with location of the Eocene/Oligocene Transition (EOT), based on chemostratigraphy (modified from Antoine et al. 2021). D, outcrop section in Shapaja where the TAR-22 locality can be observed, and where the pampatheriid tooth was discovered. E moment of the discovery of the MUSM 3965 specimen. F-H, MUSM 3965 molariform tooth in occlusal (F-G, anterior towards top) and lateral (H, anterior towards left) views.</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 2.** Teeth of Xenarthra in occlusal (A, B, D, E, and G-J) and lateral (C, F, and K) views. A-C, extant tree sloth *Bradypus*. D-F, Pleistocene ground sloth *Megatherium*. G-H, modern armadillos *Dasypus* and *Tolypeutes*, respectively. I-K, extinct Pleistocene glyptodontoid *Holmesina*. Colour code: light blue, vasodentine; dark blue, vascular canals in vasodentine; light yellow, orthodentine; dark yellow, dentinal tubules in orthodentine; light red, osteodentine; dark red, pulp cavity; light grey, cementum; dark grey, cementocyte lacunae.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Figure 3.** Tooth of Pampatheriidae indet. (MUSM 3965, early Oligocene TAR-22 locality) in occlusal (A-B, anterior towards left) and lateral (C, anterior towards left) views.</figcaption></figure>
Electronic Supplementary Material – Figure S1

Unexpected pampatheriid from the early Oligocene of Peruvian Amazonia: insights into
the tropical differentiation of cingulate xenarthrans

François Pujos IDa,b, Lionel Hautier IDc, Pierre-Olivier Antoine IDc, Myriam Boivin Id,c,d,e, Benoit Moison Idc, Rodolfo Salas-Gismondi If,g, Julia V. Tejada Idh, Rafael M. Varas-Malca Idg, Johan Yans II, and Laurent Marivaux Idc

**CONTACT** François Pujos; fpujos@mendoza-conicet.gob.ar; Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-UNCUYO-Mendoza, Av. Ruiz Leal s/n, Parque Gral. San Martín, 5500, Mendoza, Argentina

<footnote>ªInstituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-UNCUYO-Mendoza, Av. Ruiz Leal s/n, Parque Gral. San Martín, 5500, Mendoza, Argentina; ᵇConsejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, Ciudad Autónoma de Buenos Aires, Argentina; ᶜInstitut des Sciences de l'Évolution de Montpellier, Univ. Montpellier, CNRS, IRD, Place Eugène Bataillon, 34095, Montpellier, France; ᵈGrupo de Paleontología de Vertebrados, Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy (UNJu), CONICET, Av. Bolivia 1661, 4600, San Salvador de Jujuy 4600, Jujuy, Argentina; ᵉInstituto de Geología y Minería (IDGyM), Universidad Nacional de Jujuy, Av. Bolivia 1661, 4600, San Salvador de Jujuy, Argentina; ᵈBioGeoCiencias Lab, Laboratorios de Investigación y Desarrollo (LID), Facultad de Ciencias y Filosofía, Centro de Investigación para el Desarrollo Integral y Sostenible (CIDIS), Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Lima 30, Peru; ᵈDepartamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Av. Arenales 1256, Lima 14, Peru; ᵈDivision of Geological and Planetary Sciences, California Institute of Technology, CA 91125, Pasadena, United States; ᵈDepartment of Geology, Institute of Life, Earth and Environment (ILEE), University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium.</footnote>
A

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

B

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

1mm

C

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

D

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

1mm

E

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

F

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

1mm

G

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

1mm

H

<figure><img src="image_13.png" /></figure>
Figure S1. Teeth of Xenarthra in occlusal (A, C, E, and G) and lateral (B, D, F, and H) views. A-B, current tree sloth *Choloepus*. C-H, modern armadillos *Dasypus* (C-D), *Euphractus* (E-F), and *Tolypeutes* (G-H), respectively.

Color code: light blue, vasodentine; dark blue, vascular canals in vasodentine; light yellow, orthodentine; dark yellow, dentinal tubules in orthodentine; light red, osteodentine; dark red, pulp cavity; light grey, cementum; dark grey, cementocyte lacunae.
Electronic Supplementary Material – Figure S2

Unexpected pampatheriid from the early Oligocene of Peruvian Amazonia: insights into
the tropical differentiation of cingulate xenarthrans

François Pujos IDa,b, Lionel Hautier IDc, Pierre-Olivier Antoine IDc, Myriam Boivin Id,c,d,e, Benoit Moison Idc, Rodolfo Salas-Gismondi If,g, Julia V. Tejada Idh, Rafael M. Varas-Malca Idg, Johan Yans Idi, and Laurent Marivaux Idc

**CONTACT** François Pujos; fpujos@mendoza-conicet.gob.ar; Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-UNCUYO-Mendoza, Av. Ruiz Leal s/n, Parque Gral. San Martín, 5500, Mendoza, Argentina

<footnote>ªInstituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), CONICET-UNCUYO-Mendoza, Av. Ruiz Leal s/n, Parque Gral. San Martín, 5500, Mendoza, Argentina; ᵇConsejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, Ciudad Autónoma de Buenos Aires, Argentina; ᶜInstitut des Sciences de l'Évolution de Montpellier, Univ. Montpellier, CNRS, IRD, Place Eugène Bataillon, 34095, Montpellier, France; ᵈGrupo de Paleontología de Vertebrados, Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy (UNJu), CONICET, Av. Bolivia 1661, 4600, San Salvador de Jujuy 4600, Jujuy, Argentina; ᵉInstituto de Geología y Minería (IDGyM), Universidad Nacional de Jujuy, Av. Bolivia 1661, 4600, San Salvador de Jujuy, Argentina; ᵈBioGeoCiencias Lab, Laboratorios de Investigación y Desarrollo (LID), Facultad de Ciencias y Filosofía, Centro de Investigación para el Desarrollo Integral y Sostenible (CIDIS), Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Lima 30, Peru; ᵉDepartamento de Paleontología de Vertebrados, Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Av. Arenales 1256, Lima 14, Peru; ᵈDivision of Geological and Planetary Sciences, California Institute of Technology, CA 91125, Pasadena, United States; ᵈDepartment of Geology, Institute of Life, Earth and Environment (ILEE), University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium.</footnote>
<figure><img src="image_14.png" /><figcaption>Figure S2. Selection of cingulates from the Paleogene of Peru. A, MUSM 1940, partial osteoderm of an undetermined Pampatheriidae from the late Oligocene of TAR-32 locality in external view (Deseadan SALMA, Tarapoto, see Salas-Gismondi et al. 2011; Antoine et al. 2016); B-C, MUSM 3962, mobile osteoderm of the Dasypodidae *Parastegosimpsonia peruana* from TAR-21 locality in external and lateral views respectively (Tarapoto, Tinguirirican SALMA, see Antoine et al. 2021); D-E, MUSM 3963, fixed osteoderm of *P. peruana* from TAR-22 locality in external and lateral views respectively (Tarapoto, Tinguirirican SALMA, see Antoine et al. 2021); F, MUSM, osteoderm fragment of cf. *Yuruatherium* from TAR-01 locality in external view (Tarapoto, Tinguirirican SALMA, see Boivin *et al.* 2018); G-H, LACM 150606 semi movable osteoderm and LACM 150607</figcaption></figure>
movable osteoderm, respectively, of *Yuruatherium tropicalis* from the early Oligocene of Santa Roza (holotype, Tinguirirican SALMA, see Ciancio et al. 2013)

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