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International audience; Analysis of the incisor enamel microstructure of extinct and extant West Indian caviomorph rodents emphasizes a clear microstructural distinction between the Echimyidae (Capromyinae and Heteropsomyinae) among Octodontoidea and the "Heptaxodontidae" whose phylogenetic affinities are debated. All capromyines and heteropsomyines have a pattern of enamel characterized by a rectangular crystallite arrangement, which is biomechanically strongest in limiting crack propagation most efficiently (subtype [Sbt.] 3 of multiserial Hunter-Schreger bands [HSBs]). This enamel condition is exclusive to all mainland octodontoids. In stark contrast, “heptaxodontids” sampled here exhibit much less derived enamel subtypes of multiserial HSBs with parallel to acute angular crystallite arrangement (Sbt. 1 [Clidomys], Sbt. 1–2 [Elasmodontomys], and low acute Sbt. 2 [Amblyrhiza]), less well adapted for prevention of crack propagation. The incisor enamel microstructure of Amblyrhiza and Clidomys is consistent with a chinchilloid assignment, as reflected by the anatomy of their auditory region and their unusual dental pattern. For Elasmodontomys, the primitive condition of its incisor enamel is difficult to reconcile with its highly nested phylogenetic position within the Octodontoidea clade (among the Capromyinae), as recently inferred from aDNA analyses. The different enamel patterns among extinct and extant West Indian caviomorphs indicate distinct high-level taxonomic groups, but restricted to the Octochinchilloi (Octodontoidea and Chinchilloidea) among Caviomorpha. The great diversity of caviomorphs on the Caribbean islands resulted from intra-archipelago diversification through time, but their high-level phylogenetic diversity can only be explained by distinct sources, implying de facto multiple (potentially time-staggered) natural colonizations of the West Indies. The chinchilloid-compatible enamel and dental pattern characterizing Borikenomys from lower Oligocene deposits in Puerto Rico, strongly suggest a link with some of the recently-extinct "heptaxodontids" that would substantiate their much greater antiquity in the Caribbean islands.

International audience; New remains of a relatively plesiomorphic nothrotheriid sloth have been recovered from upper Miocene-aged deposits near the village of Achiri in the Altiplano of Bolivia. The new specimens appear allied to other middle and late Miocene remains from Argentina and Bolivia that have been assigned to the pseudo-genus "Xyophorus." "Xyophorus" has not previously been recognized as a distinct genus because of the paucity of material it encompasses. The new specimens, however, include a well-preserved squamosal with attached auditory region, and an isolated astragalus. These elements, which are described in detail, provide a sufficient number of distinctive characters to place the previous fossils assigned to "Xyophorus" into a new monotypic genus. Beyond exhibiting a suite of distinctive autapomorphies which justify its formal taxonomic designation, the new taxon shares several synapomorphies with more derived members of Nothrotheriidae, but also retains a number of plesiomorphies characteristic of basal megatherioid taxa, and shows a number of intermediate features. Although the new taxon is too incomplete to justify a full phylogenetic analysis, it appears to represent a basal member of Nothrotheriidae. Resolution of the taxonomic status of the genus Xyophorus awaits a better understanding of the taxonomy of early Miocene-aged basal megatherioids.

Revision of the anthracothere Parabrachyodus hyopotamoides, endemic to the Lower Miocene of the Indian subcontinent and thus far confused with Brachyodus, is made possible by the description of unpublished specimens from the Samane Nala fossil-bearing deposits of the Bugti Hills (Pakistan). This is the first biochronologically constrained occurrence for a comprehensive series of this species. The analysis of cranial and dental morphological variations based on all known specimens of Parabrachyodus allows us to provide diagnostic characters for this monotypic genus. These include a four-crested upper molar protocone unique among artiodactyls and several convergences with subfamily Anthracotheriinae, like the two puzzling distal cristae on the last upper premolar protocone. A phylogenetic analysis at the hippopotamoid level, including Parabrachyodus and the enigmatic genera Telmatodon and Gonotelma (both also endemic to the Bugti Hills), is performed for the first time. These phylogenetically related taxa turn out to be basal to the tribe Merycopotamini, leading us to propose a more inclusive definition of the diagnosis of this tribe. Our results formally establish Elomeryx as the sister-group of Merycopotamini in Bothriodontinae, and definitely locate the early evolutionary history of Merycopotamini on the Indian subcontinent.

International audience; Currently, marsupials (modern members of the Metatheria clade) are widely distributed in tropical and subtropical areas of South America, but poorly represented in the fossil record of these regions. Except for the species-rich fossiliferous localities of La Venta in Colombia, additional Miocene metatherians from tropical, equatorial South America are sparsely reported in Bolivia, Brazil, Peru, and Venezuela. Here, we introduce new metatherian remains recovered from the late middle Miocene locality of TAR-31, San Martín Department, Peru, which has been assigned to the Laventan South American Land Mammal Age (~13 Ma) by mammalian biostratigraphy. Three metatherian taxa are recognized at TAR-31: the didelphid didelphimorph ‘Thylamys’ cf. ‘T.’ colombianus, and the paucituberculatans aff. Palaeothentes and Pitheculites ipururensis sp. nov. This assemblage and the presence of a cebid primate at TAR-31 suggests predominantly humid and warm tropical conditions, with the occurrence of both forests and drier habitats in the surroundings. Comparisons with other Miocene metatherian assemblages at low and mid latitudes of South America clearly confirm close relationships between TAR-31 and La Venta (agreeing with observations based on monkeys and rodents), as well as, to a lesser extent, with Acre River local faunas and Madre de Dios (MD-67) in Brazil and Peru, respectively. The current results support the hypothesis that Western Amazonia was a single and consistent biogeographical region for land mammals over middle Miocene times, at the western edge of the Pebas Mega-Wetland System, and highlight the role of the Amazonian region concerning marsupial Neogene radiation. U-Pb analysis made on detrital zircon grains from TAR-31 gave a maximum depositional age of 17.4 ± 0.12 Ma (i.e., 4 Ma older than the biostratigraphical age), with a mixed detrital source likely comprising Precambrian (Western Amazon Craton), Neoproterozoic (Neoproterozoic mobile belts), and Phanerozoic rocks (Andes).

International audience; The Paleogene record of caviomorph rodents has substantially increased over the last decades, and their evolutionary history better understood by the discovery of their earliest representatives, so far recorded in several pre-Deseadan localities in Peruvian Amazonia. We report here the discovery of new caviomorph fossils from the Balsayacu area in Peru (TAR-55/TAR-55bis, TAR-76 and TAR-77 localities, San Martín Department). The study of this new material reveals the occurrence of four caviomorph taxa in these localities: Balsayacuy huallagaensis gen. et sp. nov., Chachapoyamys kathetos gen. et sp. nov. and Caviomorpha gen. et sp. indet. 1 and 2. It allows the revision and refinement of taxonomic assignments of previously described specimens. The first three taxa have a primitive dental pattern, as that characterizing stem Caviomorpha recorded in pre-Deseadan localities of Peru (Eocene localities of Contamana and ?late Eocene/early Oligocene Santa Rosa). We support here an Eocene age for the Balsayacu section due to the complete absence of morphologically derived taxa representing modern caviomorph superfamilies. By the presence of derived characters in Balsayacuy and Chachapoyamys compared to Canaanimys maquiensis and Cachiyacuy contamanensis from CTA-27 (Contamana, Peru; late middle Eocene), the Balsayacu section may document a time interval slightly younger than CTA-27 (which further yields Chachapoyamys cf. kathetos) and older than those of Santa Rosa and Tarapoto-Shapaja, likely documenting latest middle or early late Eocene times. These low-latitude stem caviomorph faunas provide new insights into the early evolutionary history and paleodiversity of that group immediately before the rise of modern superfamilies.

In Merceron, G., Tütken, T. & Scott, R. (Eds); International audience; Material properties of the diet of extant species is reflected by the microwear texture recorded on the enamel tooth surface, a signal that can be useful for estimating the diets of extinct species. Intra-specific dietary variations can occur between sexes or depend on seasonal vegetation cover changes in their habitat. However, these factors cannot, or very rarely, be incorporated within a paleontological context, especially if the fossil record of an extinct species is mainly composed of isolated teeth. In order to assess the impact of these factors on microwear texture features, we studied 42 wild-caught specimens of two sympatric extant species of caviomorph rodents, Proechimys cuvieri and P. guyannensis (Echimyidae, Octodontoidea) from the Cacao area located in French Guiana. Animals were captured between 2007 and 2012, in July and October, along a 1.5 kilometer transect ranging from an old secondary forest to a disturbed forest. We applied a Scale Sensitive Fractal Analysis (SSFA) to the first upper molars of these specimens. Differences of dental microwear textures were found between sexes, between months, and between habitat, leading to one species overlapping in microwear texture parameter space with the other in some cases. The results obtained help identifying which factors might drive intra-population variations in dental microwear texture. Its understanding is indeed a key-step to better interpret the dispersion observed within a given fossil sample set to obtain refined dietary reconstructions.

La révision de l'anthracothère Parabrachyodus hyopotamoides, endémique au Sous-continent indien, et jusqu'à présent souvent confondu avec Brachyodus, est fondée sur la description de spécimens inédits provenant du Miocène basal du gisement de Samane Nala dans les collines Bugti (Pakistan). Ces fossiles ont été découverts entre 1998 et 2004 dans le cadre de la « Mission Paléontologique Française au Balouchistan ». Pour la première fois depuis Forster-Cooper (1924), un échantillonnage significatif de restes crânio-dentaires appartenant à P. hyopotamoides est décrit, et cela dans un contexte biochronologique précis (Antoine et al., 2013). Dans le cadre du projet ANR Splash, nous avons mené une analyse de la variabilité morphologique dentaire et crânienne fondée sur tous les spécimens connus de Parabrachyodus. Cela nous a permis de mettre en synonymie ce taxon avec plusieurs espèces d’anthracothères initialement rapportés à Brachyodus et de réviser les caractères diagnostiques de ce genre monotypique, parmi lesquels plusieurs convergences avec la sous-famille basale des Anthracotheriinae. Une analyse phylogénétique à l’échelle des hippopotamoïdes, incluant pour la première fois Parabrachyodus ainsi que les genres énigmatiques Telmatodon et Gonotelma (deux genres pour l’instant exclusivement documentés dans les collines Bugti) a été réalisée. Ces trois taxons, phylogénétiquement proches, s'avèrent être basaux à la tribu Merycopotamini (sensu Lihoreau et al., 2016), ce qui nous amène à proposer une définition plus inclusive de la diagnose de ce clade. Nos résultats établissent formellement le genre eurasiatique Elomeryx comme le groupe-frère des Merycopotamini au sein des Bothriodontinae, et enracinent l'histoire évolutive précoce des Merycopotamini au sein du Sous-continent Indien.

International audience; A palynological assemblage including the extinct araucarian dispersed pollen, Cyclusphaera scabrata, was analysed from the Achiri locality, Bolivian Altiplano. The fossil-yielding locality of Achiri is located in the Pacajes Province, La Paz Department, in the northwestern Altiplano, Bolivia. The Achiri locality is very well known by the fossil vertebrate faunas recovered from the Mauri Formation (M6). The palynological samples come from fine-grained and plant-rich lacustrine levels lower in the same unit. An age between late middle to early late Miocene? was inferred for the palynological association studied, based on local stratigraphy and radioisotopic ages obtained higher in the series. The retrieved association is mainly represented by angiosperms; although gymnosperms, bryophytes, ferns, and freshwater algae are also documented. Compositae are the most abundant group within angiosperms, and Polylepis also occurred but in low percentages. The presence of C. scabrata in the Bolivian Altiplano expands the taxon distribution outside northern South America and provides additional evidence to infer timing and distribution routes of conifers, restricted toward the tropics during the latest Neogene. Its occurrence supports a paleoelevation of no more than 2000 m for the northern area of the Altiplano in agreement with previous results. Compositae of Fenestrites type and Polylepis occur earlier in Bolivia and C. scabrata later, comparing their occurrence in miocene microfloras from low to mid-latitudes of South America.

International audience; The vestibular system of the mammalian inner ear senses angular and linear velocity of the head and enables animals to maintain their balance. Vestibular anatomy has been studied extensively in order to link its structure to particular kinds of locomotion. Available evidence indicates that, in primates, slow-moving species show higher levels of vestibular variation than fast-moving taxa. We analysed intraspecific morphological variation and fluctuating asymmetry (FA) levels in the semicircular canal systems of six species of lorisiform primates: three slow-moving lorisids and three fast-moving galagids. Our results showed clear differences in levels of intraspecific variation between slow-moving and fast-moving taxa. Higher levels of variation were responsible for deviations from coplanarity for synergistic pairs of canals in slower taxa. Lorisids also presented higher levels of FA than galagids. FA is a better indicator of agility than intraspecific variation. These results suggest that in order to function efficiently in fast taxa, semicircular canal systems must develop as symmetrically as possible, and should minimise the deviation from coplanarity for synergistic pairs. Higher levels of variation and asymmetry in slow-moving taxa may be related to lower levels of stabilising selection on the vestibular system, linked to a lower demand for rapid postural changes.

Miocene deposits of South America have yielded several species-rich assemblages of caviomorph rodents. They are mostly situated at high and mid- latitudes of the continent, except for the exceptional Honda Group of La Venta, Colombia, the faunal composition of which allowed to describe the late middle Miocene Laventan South American Land Mammal Age (SALMA). In this paper, we describe a new caviomorph assemblage from TAR-31 locality, recently discovered near Tarapoto in Peruvian Amazonia (San Martín Department). Based on mammalian biostratigraphy, this single-phased locality is unambiguously considered to fall within the Laventan SALMA. TAR-31 yielded rodent species found in La Venta, such as the octodontoid Ricardomys longidens Walton, 1990 (nom. nud.), the chinchilloids Microscleromys paradoxalis Walton, 1990 (nom. nud.) and M. cribriphilus Walton, 1990 (nom. nud.), or closely-related taxa. Given these strong taxonomic affinities, we further seize the opportunity to review the rodent dental material from La Venta described in the Ph.D. volume of Walton in 1990 but referred to as nomina nuda. Here we validate the recognition of these former taxa and provide their formal description. TAR-31 documents nine distinct rodent species documenting the four extant superfamilies of Caviomorpha, including a new erethizontoid: Nuyuyomys chinqaska gen. et sp. nov. These fossils document the most diverse caviomorph fauna for the middle Miocene interval of Peruvian Amazonia to date. This rodent discovery from Peru extends the geographical ranges of Ricardomys longidens, Microscleromys paradoxalis, and M. cribriphilus, 1,100 km to the south. Only one postcranial element of rodent was unearthed in TAR-31 (astragalus). This tiny tarsal bone most likely documents one of the two species of Microscleromys and its morphology indicates terrestrial generalist adaptations for this minute chinchilloid.

International audience; This contribution provides the raw files for the µCT-scan data and renderings of the three-dimensional digital models of two fossil teeth of a geomyin geomorph rodent (Caribeomys merzeraudi), discovered from lower Oligocene deposits of Puerto Rico, San Sebastian Formation (locality LACM Loc. 8060). These fossils were described, figured and discussed in the following publication: Marivaux et al. (2021), An unpredicted ancient colonization of the West Indies by North American rodents: dental evidence of a geomorph from the early Oligocene of Puerto Rico. Papers in Palaeontology. https://doi.org/10.1002/spp2.1388

International audience; Extinct terrestrial sloths are common elements of the late Cenozoic South American fossil record. Among them, Mylodontinae species were particularly abundant in the Americas throughout the Pleistocene epoch, and their anatomy is relatively well known. In contrast, less information is available from the Neogene record and particularly from localities at low latitudes, with an additional and considerable bias in favor of craniodental rather than postcranial remains. In this contribution, we provide comparative descriptions of several postcranial bony elements ascribed to Simomylodon uccasamamensis, a moderatesized extinct mylodontine from the Andean Altiplano. This species was particularly abundant during latest Miocene–late Pliocene times in the high altitudes of the Andean Cordillera, and so far represents the best known mylodontine from the Neogene of South America. Its anatomy is compared with that of several extinct terrestrial sloths, with the aim of using the observed morphologies to elucidate taxonomy, phylogeny, and locomotion. From a morphofunctional perspective, the postcranium of S. uccasamamensis is consistent with that of a terrestrial graviportal quadruped, with moderate climbing and digging capabilities.

International audience; Since 2012, we have investigated a stratigraphic section encompassing the late Eocene–earliest Oligocene interval at Shapaja (Tarapoto area, Peruvian Amazonia, ca. 7°S), through paleontological and geological fieldwork. The measured sedimentary series (120 m-thick [West] plus 90 m-thick [East]), assigned to the upper member of the Pozo Formation, records fluvial micro-conglomeratic lenses intercalated with floodplain and evaporite-rich fine red deposits, estuarine/coastal-plain tidally-influenced fine sandstones, and oxbow lake nodule-rich blue clays. This sedimentary shift coincides locally with the demise of the large Eocene coastal-plain wetland known as Pozo System. The late Eocene–early Oligocene Shapaja section was extensively sampled for chemostratigraphy (δ13C on dispersed organic matter and pedogenic carbonate nodules), which in turn allowed for refining the location of the Eocene-Oligocene Transition (EOT) and other climatic events recognized at a global scale (i.e., Oi-1 and Oi-1a). The section has yielded nine fossil localities with plant remains (leaves, wood, charophytes, and palynomorphs), mollusks, decapods, and/or vertebrates (selachians, actinopterygians, lungfishes, amphibians, sauropsids, and mammals), documenting ~130 distinct taxa. Four localities of the upper member of the Pozo Formation at Shapaja predate the EOT, one is clearly within the EOT, while four are earliest/early Oligocene in age. The small leaf impressions found along the Shapaja section could be indicative of dry and/or seasonal conditions for this region throughout and after the EOT. Monkeys, indicative of tropical rainforest environments, are only recorded in a latest Eocene locality (TAR-21). Two biotic turnovers are perceptible in the selachian, metatherian, and rodent communities, well before the EOT [~35–36 Ma] and a few hundred thousand years after the EOT [~33 Ma]. The latter turnover seems to be primarily related to a global sea-level drop (ichthyofauna: marine-littoral elements replaced by obligate freshwater taxa) and/or the onset of a drier and more seasonal climate in early Oligocene times (terrestrial components). Changes in the structure of the Shapaja paleocommunities were mostly driven by the flexural subsidence during the late Eocene, and then globally driven by the earliest Oligocene climatic deterioration.

Anthracotheres dispersed from Asia toward Africa at least three times: at the Eocene/Oligocene transition, during the early Miocene and later during the Miocene. Those dispersals are important datum events for African Tertiary biochronology. New fossil remains of early Libycosaurus, the genus implicated in the late Miocene dispersal, are described from a new Tunisian locality of the Kasserine area. The new fossils enhance the hypodigm of Libycosaurus algeriensis and increase the resolution of the phylogenetic position of this species using cladistics analysis. The inclusion of the genus Libycosaurus within the well-described Merycopotamus lineage allows us to constrain its dispersal time. Dispersal of this anthracothere from the Indian sub-continent to Africa was probably facilitated by sea level decrease during the early Tortonian, just preceding the Hipparion dispersal event. This new age estimation refines the resolution of the succession of late Miocene deposits in Maghreb and frames the date of the onset of the Sahara.

International audience; The West Indies are a natural laboratory for the study of biogeography and evolution, especially for mammals. The modality of their arrival in the Caribbean islands is a highly controversial issue, and palaeontological evidence remains particularly elusive. Lower Oligocene deposits of Puerto Rico (c. 29.5 Ma) have recently yielded the oldest archipelago rodents, with teeth of two chinchilloid caviomorphs of South American origin. Here we report the discovery of additional dental remains from the same level, testifying to the occurrence of another rodent group. Their morphology is singular but otherwise characteristic of North/Central American geomyin geomorphs (including extant kangaroo rats, pocket mice, and pocket gophers), and leads us to propose here a new taxon: Caribeomys merzeraudi gen. et sp. nov. The evidence of geomorphs in the West Indies challenges the view that all extinct and extant Antillean rodents derived from South American sources. The morphological singularity of this Puerto Rican geomorph also suggests an early split of this insular lineage from coeval mainland counterparts, and its dispersal towards the West Indies sometime around the Eocene–Oligocene transition. This unexpected rodent adds to the few cases of Antillean terrestrial vertebrates of North American origins, such as solenodonotan eulipotyphlans. In the absence of subaerial land connections between both landmasses, an overwater dispersal may explain mid-Palaeogene colonization of the West Indies by geomorph rodents.

International audience; HGL50 is a latest Early-early Middle Eocene vertebrate-bearing locality located in Western Algeria. It has produced the richest and most diverse fauna of amphibians and squamate reptiles reported from the Palaeogene of Africa. Moreover, it is one of the rare faunas including amphibians and squamates known from the period of isolation of Africa. The assemblage comprises 17 to 20 taxa (one gymnophionan, one probable caudate, three to six anurans, seven 'lizards', and five snakes). Two new taxa were recovered: the anuran Rocekophryne ornata gen. et sp. nov. and the snake Afrotortrix draaensis gen. et sp. nov. The locality has also yielded the first confirmed anilioid snake, the first Palaeogene gymnophionan, and probably the first caudate from the Palaeogene (and possibly from the Tertiary) of Africa. The presence of a caudate at that time in Africa would be of particular interest; unfortunately, the available material does not permit a definitive identification. The fauna comprises Gondwanan and more specifically West Gondwanan vicariants, probably autochthonous groups and a Eurasian immigrant (assuming that the identification of the caudate is accurate). The fauna from HGL50 is clearly distinguished from the few other Eocene assemblages of Africa. However, if this results largely from differences in geological ages, geographic positions of the localities and mainly differences in environments took a part in the composition of the faunas.

International audience; This contribution contains the 3D models of the fossil teeth of two chinchilloid caviomorph rodents (Borikenomys praecursor and Chinchilloidea gen. et sp. indet.) discovered from lower Oligocene deposits of Puerto Rico, San Sebastian Formation (locality LACM Loc. 8060). These fossils were described and figured in the following publication: Marivaux et al. (2020), Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial rodent colonization of the West Indies. Proceedings of the Royal Society B. http://dx.doi.org/10.1098/rspb.2019.2806

International audience; The Honda Group of La Venta, Colombia, has yielded a wide array of crown platyrrhine primates, documenting the late Middle Miocene epoch (ca. 13.1–12.6 Ma, Laventan South American Land Mammal Age). Although exceptional, this record represents only a snapshot of the evolutionary history of New World monkeys because virtually none of the primate taxa recorded at La Venta had so far been found elsewhere. We describe here few dental remains of a cebine platyrrhine discovered from Laventan deposits in the San Martín Department of Peru (Peruvian Amazonia). The primate dental specimens from that new fossil-bearing locality (TAR-31) are strongly reminiscent morphologically of the teeth of Neosaimiri fieldsi from La Venta. However, given that several aspects of the dental variability from TAR-31 are unknown, we prefer to provide an assignment with open nomenclature (i.e., Neosaimiri cf. fieldsi), instead of formally referring these remains to N. fieldsi, pending the discovery of additional specimens. The occurrence of Neosaimiri in Peru, in coeval deposits of La Venta, thus represents a second and southernmost record of that low-latitude genus in the Neotropics, thereby demonstrating its wide distribution along the northwestern edge of the Pebas Mega-Wetland System, in tropical western South America.

The current note aims to respond to the comments of Verzi et al. (2018) on our published works (Boivin and Marivaux 2018). Regarding the homologies of the mesial cristids in lower molars in octodon...

International audience; Dental homologies and evolutionary transformations within caviomorph rodents have long been disputed. Here, we participate in these debates in providing new insights from the dental morphology of Paleogene caviomorphs from Peruvian Amazonia (Contamana and Shapaja). Their analyses and comparisons with many hystricognaths allow (1) to generalize some hypotheses previously proposed about occlusal morphology of caviomorph cheek teeth, and (2) to propose new ones. In caviomorphs, the third crest of upper teeth would correspond either to a mesoloph or to a mesolophule or to a combination of both. The transformation from a pentalophodont pattern to a tetralophodont pattern would be explained by the disappearance of the metaloph. Likewise, the transformation from a tetralophodont pattern to a trilophodont pattern is observed by the loss of the third crest. A direct transformation from a pentalophodont pattern to a trilophodont pattern is also observed. Concerning lower teeth, discrepancies of homologies are centered on the mesial cristids, which can be notably distinguished depending on their compositions and connections with other structures. The ancestral patterns of caviomorph lower molars and dp4s were likely tetralophodont and pentalophodont, respectively. However, schemes with five and four (even three) transverse cristids cannot be ruled out for the two loci, respectively.

Rodent enamel microstructure has been extensively investigated, primarily on the basis of 2D electronic microscopy data. The nature and dynamics of the ameloblasts (the enamel-secreting cells) have also been well studied. However, critical issues still remain surrounding exactly how the ameloblasts produce the astonishing microstructural complexity of enamel, and how this subtle architecture evolved through time. In this article, we used a new methodology based on confocal laser microscopy to reconstruct the enamel microstructure of rodent incisors in three dimensions (3D) with the ameloblasts in situ. We proposed interpretations regarding the possible relationships between the workings of the ameloblasts and the resulting enamel prisms, especially how the phenomenon of decussation is generated. Finally, we were able to represent the two main types of modern rodent incisor microstructures (uniserial and multiserial decussations), as a set of parameters that have been entered into the 3D enamel simulation software Simulenam to generate 3D models that can be digitally manipulated. Associating 2D data of incisor enamel microstructure of fossil rodents and Simulenam, it was then possible to better understand how the various decussation parameters evolved through time and gave rise to the two modern microstructure types from the same ancestral type (pauciserial). This study also confirmed that rodent and artiodactyl enamel do not share the same mechanism of decussation formation. Anat Rec, 302:1195-1209, 2019. © 2018 Wiley Periodicals, Inc.

International audience; This paper provides a revision of the early and middle Eocene European rodents previously referred to as Ischyromyoidea, including taxa considered to be at the origin of the Theridomorpha. The use of an accurate dental terminology and a better understanding of the size and shape of their infra-orbital foramen (i.o.f.) led us to a substantial revision of this group, which allowed to better characterize them and to appreciate their variability. On these bases, phylogenetic analyses (cladistic and standard Bayesian approaches) of early Ypresian to late Priabonian European rodent species were undertaken in order to highlight the root of the early Theridomorpha and its content. The phylogeny was established based on 343 characters (338 dental) through 45 early Paleogene taxa. The ingroup included on one hand a few North American genera (Reithroparamys, Microparamys, and Acritoparamys) and European ones (Eogliravus, Ailuravus, Corbarimys, Meldimys, Euromys, Plesiarctomys, and Pseudoparamys) considered until now as being related with the North American superfamily Ischyromyoidea. On the other hand, it included genera close to the root of the Theridomorpha (Sparnacomys, Pantrogna, and Hartenbergeromys) and early Theridomyoidea (Masillamys, Protadelomys, and some Pseudosciuridae). The phylogenetic results obtained via the two distinct reconstruction approaches are consistent in virtually all relationships. The proposed systematics here derives from these phylogenetic results. This phylogenetic context led us to change the suprafamilial, familial, subfamilial or generic attribution of several species. Characters of Theridomorpha, like the obliquely developed postprotocristid allied with the occurrence of a metalophulid I, have been found in genera previously considered as Ischyromyidae (Pseudoparamys, Euromys, Sparnacomys, Meldimys, Pantrogna, and Hartenbergeromys) as well as the large i.o.f., when preserved (Pseudoparamys, Hartenbergeromys, and Masillamys). Based on these morphological observations and new phylogenetic considerations, the content of the Theridomorpha clade is here enlarged, thereby extending back the first theridomorph radiations to the early Eocene. Aside, a new taxon (Reinomys rhomboides gen. and sp. nov.) is described from Avenay. In addition, a new genus, Auroremys, is created for the species subita (Comte et al., 2012) from Chery-Chartreuve.

International audience; Bulk sampling of an indurated glauconic sandstone horizon from Djebel el Kébar, Central Tunisia, yielded a moderately diversified assemblage of elasmobranchs (sharks and rays), dating from the late Middle Eocene (mid Bartonian). Here, 10 new taxa (nine new species and three new genera) are described among a total diversity of 33 species. These new taxa highlight the rise of mid-large predator lineages of modern nearshore seas and fill a substantial gap in the sporadic fossil record of the late Middle Eocene. Comparisons of this assemblage with other Middle-Late Eocene faunas from the Tethys seaway indicate that this Tunisian fauna shares more similarities with Late Eocene than with early Middle Eocene assemblages. This suggests that the major shift observed in tropical elasmobranch communities from the Late Eocene, with for instance the appearance of large Carcharhinids replacing Lamniforms, began during the late Middle Eocene. Such a biotic shift could be linked to the warm conditions recorded ca. 41 Ma, known as the Middle Eocene Climatic Optimum (MECO), which was characterized by a short temperature increase of all marine waters.

International audience; This contribution contains the 3D models of the fossil teeth of a small-bodied platyrrhine primate, Neosaimiri cf. fieldsi (Cebinae, Cebidae, Platyrrhini) discovered from Laventan deposits (late Middle Miocene) of Peruvian Amazonia, San Martín Department (TAR-31: Tarapoto/Juan Guerra vertebrate fossil-bearing locus n°31). These fossils were described and figured in the following publication: Marivaux et al. (2020), New record of Neosaimiri (Cebidae, Platyrrhini) from the late Middle Miocene of Peruvian Amazonia. Journal of Human Evolution. https://doi.org/10.1016/j.jhevol.2020.102835

By their past and present diversity, rodents are among the richest components of Caribbean land mammals. Many of these became extinct recently. Causes of their extirpation, their phylogenetic affinities, the timing of their arrival in the West Indies and their biogeographic history are all ongoing debated issues. Here, we report the discovery of dental remains from Lower Oligocene deposits (ca29.5 Ma) of Puerto Rico. Their morphology attests to the presence of two distinct species of chinchilloid caviomorphs, closely related to dinomyids in a phylogenetic analysis, and thus of undisputable South American origin. These fossils represent the earliest Caribbean rodents known thus far. They could extend back to 30 Ma the lineages of some recently extinct Caribbean giant rodents (ElasmodontomysandAmblyrhiza), which are also retrieved here as chinchilloids. This new find has substantial biogeographic implications because it demonstrates an early dispersal of land mammals from South America to the West Indies, perhaps via the emergence of the Aves Ridge that occurredca35–33 Ma (GAARlandia hypothesis). Considering both this new palaeontological evidence and recent molecular divergence estimates, the natural colonization of the West Indies by rodents probably occurred through multiple and time-staggered dispersal events (chinchilloids, then echimyid octodontoids (spiny rats/hutias), caviids and lastly oryzomyin muroids (rice rats)).

The Serra do Mar Atlantic forest (Brazil) shelters about 15 different species of caviomorph rodents and thus represents a unique opportunity to explore resource partitioning. We studied 12 species with distinct diets using dental microwear texture analysis (DMTA). Our results revealed differences (complexity, textural fill volume, and heterogeneity of complexity) among species with different dietary preferences, and among taxa sharing the same primary dietary components but not those with similar secondary dietary preferences (heterogeneity of complexity). We found three main dietary tendencies characterized by distinct physical properties: consumers of young leaves had low complexity; bamboo specialists, fruit and seed eaters, and omnivorous species, had intermediate values for complexity; grass, leaf, and aquatic vegetation consumers, had highly complex dental microwear texture. Dietary preferences and body mass explained a major part of the resource partitioning that presumably enables coexistence among these rodent species. DMTA was useful in assessing what foods contributed to resource partitioning in caviomorphs. Our database for extant caviomorph rodents is a prerequisite for interpretation of dental microwear texture of extinct caviomorph taxa, and thus for reconstructing their diets and better understanding the resource partitioning in paleocommunities and its role in the successful evolutionary history of this rodent group.

This paper clarifies the identification of the three species referred by Tobien (1954) to the genus Masillamys from Messel, and more specifically provides a revision of their diagnosis and differential dental features, using an updated terminology. Based on specimens better preserved than the holotype (M. beegeri), it appears that this genus had an infraorbital area more hystricomorphous than sciuromorphous. As the genus shares dental features – like a long oblique postprotocristid or the occurrence of a metalophid I on the lower molars, the relatively well-developed hypocone on the upper molars, as well as hystricomorphy –, notably with Hartenbergeromys and Pantrogna, Masillamys is here included among the basal Theridomorpha.

International audience; This paper provides a revised and updated description and identification of the rodents from Santpedor-2 (northeastern Spain). The age of this locality is particularly relevant, because it is one of the few European sites assigned to the early Oligocene that has yielded primate remains. However, the rodent assemblage from this site has never been described in detail, and therefore the Oligocene age of this locality remained tentative. Despite the scarcity of the material, the rodents from Santpedor-2 are characteristic enough either to be identified as already known species, or at least compared with close species. Eight different rodent taxa were recognized. Among them, the theridomyid Ectropomys exiguus, which is recorded only in late Eocene localities, and the glirid Glamys devoogdi, which is known in both latest Eocene and early Oligocene localities. The other taxa are found only in Oligocene localities, and consist of the theridomyid Paratheridomys margaritae and members of two families that arrived in Europe at the beginning of the Oligocene: eomyids (Eomys sp.) and cricetids (Eucricetodon atavus, cf. Heterocricetodon sp., cf. Pseudocricetodon sp.). Finally, another theridomyid (Issiodoromyinae) seems to correspond to a new species and new genus, the main features of which correspond to early Oligocene evolutionary grades. This rodent assemblage from Santpedor-2 is assigned to the early Oligocene, mainly on the basis of the presence of immigrant rodents that reached Europe in relation with the Grande Coupure (cricetids and eomyids). This dating is notably supported by the presence of P. margaritae together with Glamys devoogdi, both being found in Hoogbutsel (early Rupelian, MP21). Only one rodent (E. exiguus) represents an Eocene relict, as is the case of Pseudoloris, the only primate recorded in this locality. Therefore, this study supports the Oligocene age of Santpedor-2 and then the persistence of omomyid primates in the Iberian Peninsula (at least locally) after the Grande Coupure.

Although phylogenetic trees imply Asia as the ancestral homeland of the Hystricognathi clade (Rodentia: Ctenohystrica), curiously the oldest known fossil occurrences of hystricognathous rodents are not from Asia, but from Africa and South America, where they appear suddenly in the fossil record of both landmasses by the Late Middle Eocene. Here we performed cladistic and Bayesian (standard and tip-dating analyses) assessments of the dental evidence documenting early ctenohystricans, including several Asian 'ctenodactyloids', virtually all Palaeogene Asian and African hystricognaths known thus far and two representatives of the earliest known South American hystricognaths. Our results provide a phylogenetic context of early hystricognaths (with implications on systematics) and suggest that some Eocene Asian 'ctenodactyloids' could be considered as stem hystricognaths and pre-hystricognaths, although they were not recognized as such originally. However, this view does not fill the gap of the Eocene Asian hystricognath record, as the proposed results imply many ghost lineages extending back to the Middle Eocene for several Asian and African taxa. They also imply a complex early historical biogeography of the group, involving multiple dispersal events from Asia to Africa (and possibly from Africa back to Asia) and then to South America sometime during the Middle Eocene. Based on these phylogenetic considerations, we discuss the emergence of hystricognathous rodents from a morpho-anatomical perspective by analysing the differentiation of their masticatory apparatus and chewing movements, notably through the evolution of their dental patterns. Fil: Marivaux, Laurent. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia Fil: Boivin, Myriam. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia. Universite de Nantes; Francia

Seven hystricognaths and five anomaluroids have been recently described from the earliest Oligocene of the Dakhla (DAK C2) region of Morocco, based primarily on isolated cheek teeth. Here, we analyzed the enamel microstructure of thirty associated isolated fragments of incisors. Among these specimens, only three display an early stage of uniserial Hunter-Schreger bands (HSBs), with mostly a single prism per band, but also occasionally two prisms per band (in two specimens), and a thin interprismatic matrix (IPM) that runs parallel to the prism direction, thereby documenting incisors of anomaluroids. All other sampled incisors display an enamel with multiserial HSBs, thereby documenting hystricognaths. For these latter, we recorded primarily an IPM crystallite arrangement describing the subtype 2 of multiserial HSBs, but with variation including a wide amplitude in the angle (acute) formed between the crystallites of IPM and those of the prisms, some variations in the frequency of the IPM sheet anastomoses, in the number of prisms per HSBs, and variations in the inclination of the HSBs. The absence of the subtypes 2–3 and 3 of multiserial HSBs in DAK C2 suggests that African hystricognathous rodents had still not achieved these most resistant multiserial HSBs at that time. The drier, cooler climatic regime of the early Oligocene, having increased the fragmentation and opening of habitats, might have played a role in the subsequent selection of taxa having acquired a more resistant incisor enamel. Fil: Marivaux, Laurent. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia Fil: Boivin, Myriam. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia Fil: Adnet, Sylvain. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia Fil: Benammi, Mohamed. Université Ibn Tofail; Marruecos Fil: Tabuce, Rodolphe. Université Montpellier II; Francia. Centre National de la Recherche Scientifique; Francia Fil: Benammi, Mouloud. Université de Poitiers; Francia

We report here a new record of the giant caviomorph Phoberomys corresponding to a fragmentary mandible from the Monte Salvado area, Peruvian Amazonia (Madre de Dios Department). We describe this specimen and compare it with the material previously attributed to Phoberomys. The mandibular fragment is referred to as Phoberomys sp. Found as float on a bank of the Río Las Piedras, it has been hypothetically assigned a late Miocene age, due to the local/regional stratigraphic and lithologic context. This specimen constitutes the second record of Phoberomys in Peru. For the first time, the pattern of p4s and lower molars in Phoberomys was analyzed and compared to a large taxonomic sample (including Paleogene–Recent chinchilloids and other caviomorphs) in order to progress the understanding of the homology of dental structures in this genus. For p4s and lower molars, the position of the protoconid in Phoberomys and other chinchilloids (Drytomomys sp., Potamarchus, Eumegamys, Gyriabrus, Isostylomys, and Tetrastylus) is ambiguous, and as a result we propose two alternative homology hypotheses for these taxa: protoconid within the first and second laminae or within the third lamina on juvenile specimens. The knowledge of a comprehensive ontogenetic sequence in extinct and extant chinchilloids, associated with more complete palaeontological records, would likely allow for a clarification of these homology ambiguities. Fil: Boivin, Myriam. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina. Universite de Nantes; Francia. Centre National de la Recherche Scientifique; Francia Fil: Antoine, Pierre Olivier. Université Montpellier II; Francia Fil: Benites Palomino, Aldo. Universidad Nacional Mayor de San Marcos; Perú Fil: Marivaux, Laurent. Université Montpellier II; Francia Fil: Salas Gismondi, Rodolfo. Universidad Nacional Mayor de San Marcos; Perú

Objectives: Undoubted fossil Cebidae have so far been primarily documented from the late middle Miocene of Colombia, the late Miocene of Brazilian Amazonia, the early Miocene of Peruvian Amazonia, and very recently from the earliest Miocene of Panama. The evolutionary history of cebids is far from being well-documented, with notably a complete blank in the record of callitrichine stem lineages until and after the late middle Miocene (Laventan SALMA). Further documenting their evolutionary history is therefore of primary importance. Material: Recent field efforts in Peruvian Amazonia (Contamana area, Loreto Department) have allowed for the discovery of an early late Miocene (ca. 11 Ma; Mayoan SALMA) fossil primatebearing locality (CTA-43; Pebas Formation). In this study, we analyze the primate material, which consists of five isolated teeth documenting two distinct Cebidae: Cebus sp., a medium-sized capuchin (Cebinae), and Cebuella sp., a tiny marmoset (Callitrichinae). Results: Although limited, this new fossil material of platyrrhines contributes to documenting the post-Laventan evolutionary history of cebids, and besides testifies to the earliest occurrences of the modern Cebuella and Cebus/Sapajus lineages in the Neotropics. Regarding the evolutionary history of callitrichine marmosets, the discovery of an 11 Ma-old fossil representative of the modern Cebuella pushes back by at least 6 Ma the age of the Mico/Cebuella divergence currently proposed by molecular biologists (i.e., ca. 4.5 Ma). This also extends back to>11 Ma BP the divergence between Callithrix and the common ancestor (CA) of Mico/Cebuella, as well as the divergence between the CA of marmosets and Callimico (Goeldi’s callitrichine). Discussion: This discovery from Peruvian Amazonia implies a deep evolutionary root of the Cebuella lineage in the northwestern part of South America (the modern western Amazon basin), slightly before the recession of the Pebas mega-wetland system (PMWS), ca. 10.5 Ma, and wellbefore the subsequent establishment of the Amazon drainage system (ca. 9–7 Ma). During the late middle/early late Miocene interval, the PMWS was seemingly not a limiting factor for dispersals and widespread distribution of terrestrial mammals, but it was also likely a source of diversification via a complex patchwork of submerged/emerged lands varying through time.

A state-of-the-art review of the Cenozoic fossil record from Western Amazonia is provided, based on literature and new data (regarding Paleogene native ungulates). It allows summarizing the evolution and dynamics of middle Eocene–Holocene mammalian guilds, at the level of species, families, and orders. Major gaps in the Western Amazonian mammal record occur in the pre-Lutetian and early Miocene intervals, and in the Pliocene epoch. Twenty-three orders, 89 families, and 320 species are recognized in the fossil record, widely dominated by eutherians from the middle Eocene onward. Probable Allotheria (Gondwanatheria) occur only in the earliest interval, whereas Metatheria and Eutheria are conspicuous components of any assemblage. Taxonomic diversity was probably fairly constant at the ordinal level (~12–14 orders in each time slice considered) and much more variable in terms of family and species richness: if most intervals are characterized by 40–50 co-occurring species and 19–31 co-occurring families, the early Miocene period illustrates a depauperate fauna (21 species, 17 families), strongly contrasting with the late Miocene climactic guild (82 species, 38 families). Recent mammalian taxonomic diversity from Western Amazonia (12 orders, 37 families, and 286 species) is at odds with all past intervals, as it encompasses only three orders of South American origin (Didelphimorphia, Cingulata, and Pilosa) but four North American immigrant orders (Artiodactyla, Perissodactyla, Carnivora, and Lagomorpha). In terms of taxonomic diversity, recent mammalian guilds are fully dominated by small-sized taxa (Chiroptera, Rodentia, and Primates). This overview also confirms the scarcity of large mammalian flesh-eaters in ancient Neotropical mammalian assemblages. The pattern and the timing of mammalian dispersals from northern landmasses into Western Amazonia are not elucidated yet. Fil: Antoine, Pierre Olivier. Université de Montpellier; Francia Fil: Salas Gismondi, Rodolfo. Université de Montpellier; Francia. Universidad Nacional Mayor de San Marcos; Perú Fil: Pujos, François Roger Francis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Ganerød, Morgan. Geological Survey of Norway; Noruega Fil: Marivaux, Laurent. Université de Montpellier; Francia

Weprovide a synopsis of ~60million years of life history in Neotropical lowlands, based on a comprehensive survey of the Cenozoic deposits along the Quebrada Cachiyacu near Contamana in PeruvianAmazonia. The 34 fossilbearing localities identified have yielded a diversity of fossil remains, including vertebrates,mollusks, arthropods, plant fossils, and microorganisms, ranging from the early Paleocene to the lateMiocene–?Pliocene (N20 successive levels). This Cenozoic series includes the base of the Huchpayacu Formation (Fm.; early Paleocene; lacustrine/ fluvial environments; charophyte-dominated assemblage), the Pozo Fm. (middle + ?late Eocene; marine then freshwater environments; most diversified biomes), and complete sections for the Chambira Fm. (late Oligocene–late early Miocene; freshwater environments; vertebrate-dominated faunas), the Pebas Fm. (late early to early late Miocene; freshwater environments with an increasing marine influence; excellent fossil record), and Ipururo Fm. (late Miocene–?Pliocene; fully fluvial environments; virtually no fossils preserved). At least 485 fossil species are recognized in the Contamana area (~250 ‘plants’, ~212 animals, and 23 foraminifera). Based on taxonomic lists from each stratigraphic interval, high-level taxonomic diversity remained fairly constant throughout themiddle Eocene–Miocene interval (8-12 classes), ordinal diversity fluctuated to a greater degree, and family/species diversity generally declined, with a drastic drop in the early Miocene. The Paleocene–?Pliocene fossil assemblages from Contamana attest at least to four biogeographic histories inherited from (i) Mesozoic Gondwanan times, (ii) the Panamerican realm prior to (iii) the time of South America’s Cenozoic “splendid isolation”, and (iv) Neotropical ecosystems in the Americas. No direct evidence of any North American terrestrial immigrant has yet been recognized in the Miocene record at Contamana., Facultad de Ciencias Naturales y Museo

Among the flourishing Muroidea, the Eucricetodontinae constitute the most diversified subfamily of the Eurasian Palaeogene. Early representatives, such as Atavocricetodon and Eucricetodon, are notably characterized by their simple and primitive dental morphology. As a result, it appears very difficult to discriminate these genera according to their dental morphology, and that is emphasized by their imprecise diagnosis. Here, we aim at challenging the taxonomic validity of Atavocricetodon, frequently considered as a grade of Eucricetodon. We chose to investigate the outline of first upper molars for four species of Atavocricetodon and seven of Eucricetodon, to avoid confusions made by their occlusal dental characters. The outline analysis involves samples of ten molars and was realized by using Elliptic Fourier Transforms. Incisor enamel microstructures were investigated as well in four species. Results revealed that if a significant difference exists between the global dental shape of Atavocricetodon and Eucricetodon, outline morphospaces of the considered species generally overlap as displayed by the multivariate analysis and the hierarchical clustering. This is partly explained by the high intrageneric shape variation, which might correspond to different Oligocene lineages of Eucricetodontinae. Such variation is also due to Atavocricetodon paaliense, which could rather belong to another genus, the pseudocricetontine Kerosinia. More generally, there is no real apomorphy which permits to distinguish these genera, because incisor enamel microstructure patterns are highly variable and a few types are shared by both genera. Atavocricetodon cannot thus be retained neither as a genus, nor as a morphosubgenus of Eucricetodon

International audience; A post-Priabonian fluviatile debris-flows in Mabrouk (MBK), Djebel Chambi – Tunisia, have yielded a surprisingly rich assemblage of reworked marine elasmobranchs (23 taxa of sharks and rays). By comparison with their sub-coeval counterparts from northeastern Africa, this assemblage suggests an age ranging from the latest Priabonian up to the earliest Rupelian for the close marine deposit from where they were likely reworked. Moreover, it highlights the widespread east-west distribution of sharks and rays along North African coasts, a distribution that reflects the existence of roughly similar tropical environmental conditions in northern latitudes of Africa at that time. This discovery indicates that the Neotethysian elasmobranch communities remained particularly well diversified around the global cooling recorded at the Eocene/Oligocene transition.