Carnivoran mammals (cats, dogs, bears, seals, etc.) and their kin radiated during the Palaeogene, among other carnivorous clades (hyaenodonts, mesonychians, and oxyaenodonts). This radiation has often been framed as a competition ultimately won by carnivorans, but the data supporting this hypothesis largely originate from North America. We derive body mass (BM) from dental measurements in European hyaenodonts, mesonychians, oxyaenodonts, and carnivoramorphans ranging from the latest Palaeocene to the end of the Oligocene (MP 6-30; 57.2-23.3 Ma) and compare those with North American data. We show that European assemblages tell a different story, with a marked increase of the disparity of carnivoramorphan BMs at and after the Middle Eocene Climatic Optimum (MECO; 40 Ma), with no clear effect on hyaenodonts. The 'Grande Coupure' (Eocene-Oligocene transition, approx. 34-33.5 Ma) marks the onset of a progressive decrease in the mean BM of hyaenodonts, while carnivoramorphans continue their rise initiated around the MECO. The observed BM patterns therefore do not follow the expected double-wedge pattern of competitive replacement and are possibly best explained by climate change-induced biodiversity dynamics.

Perissodactyls were a diverse order of mammals in the Northern Hemisphere during the Paleogene, but very few species remain today. They first appear during the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) on the three continents of the Northern Hemisphere. Because they lack modern diversity, the study of their evolutionary history remains difficult, relying almost exclusively on fossils. In addition, their origin and early diversification remain elusive since all main groups appear at the same time with several genera and are already diverse, contrary to other modern mammal orders. Here, we investigate the early evolution of perissodactyls by analyzing a new dataset focusing on early species to obtain a new expansive phylogeny. This new topology, in combination with new observations and comparisons demonstrates that several genera are synonymous, simplifying the evolutionary picture of early perissodactyls. We show that the number of genera was overestimated and should be significantly reevaluated. These results also highlight fast dispersals of two genera, Pliolophus and Cardiolophus, on the three Northern continents, reflecting that of other modern mammals. The phylogeny also supports a potential Indo-Pakistani origin of perissodactyls. In addition, this large-scale phylogeny shows that many species that were named as "Hyracotherium" in the past (or sometimes "Eohippus", the "dawn-horse") and considered as "horses", are not actually closely related to horses (Hippomorpha), including Hyracotherium itself, but can be considered as basal perissodactyls.

The land-to-water transition of cetacean mammals is a case study illustrating morphological transformation over time. The earliest cetaceans, still able to walk on land, document spectacular transitional states of their skull and body, allowing a step-by-step reconstruction of their adaptations to the aquatic environment. However, their highly derived carnivorous teeth appear abruptly in the fossil record and the earliest evolutionary history of their dentition remain poorly understood. Here we describe the most basal representative of Cetacea, Kalakocetus aurorae gen. et sp. nov., from the Eocene of India. Its unprecedented dental morphology bridges the gap between the shearing molars of early carnivorous cetaceans and the crushing molars of their closest terrestrial relatives. Functional analyses point to a carnivorous diet implying shearing movement of the jaw and a loss of crushing function of the third molar. The intermediate morphology of K. aurorae gen. et sp. nov. provides the missing element critical to the understanding of the emergence of the carnivorous dental pattern of cetaceans. Its basal position in the cetacean tree sheds new light on cetacean origins and dental evolution.

An exquisitely preserved, isolated partial petrosal with associated fragmentary stapes is described from the Vastan Lignite Mine (Gujarat, India), dated to the early Eocene (~54.5 Ma). Several anatomical traits (e.g., large petrosal plate; posterolateral entry of the internal carotid artery to the tympanic cavity; bony tubes surrounding the internal carotid artery and stapedial artery) allow the specimen to be confidently allocated to Euprimates, making it likely the oldest and among the best-preserved petrosals known for this clade. Of the two superfamilies of primates known from Vastan Mine-Adapoidea and Omomyoidea-the anatomy of the petrosal is more consistent with an attribution to Adapoidea (e.g., epitympanic crest present, no bony tube surrounding the promontorial artery). Body mass estimation indicates that the petrosal came from a small species (≤186 g), suggesting it most likely pertains to the asiadapid Marcgodinotius indicus, the smaller of the two named adapoids known from the Vastan fauna. Locomotor reconstructions based on semicircular canal radii of curvature and inter-canal angles are incongruent, with the former being more consistent with postcranial interpretations of the asiadapids as relatively cautiously moving taxa without specializations for leaping, while the latter suggests a more active form of locomotion. The specimen exhibits traits inferred to be primitive (e.g., lack of a bony tube for promontorial artery, shallow epitympanic recess, short cochlea), which are consistent with the idea that Asiadapidae constitutes a very early branch of the adapoid tree. Indeed, this specimen is similar to what might be expected for a basal strepsirrhine.

A highly debated topic in eusuchian systematics has been the placement of "thoracosaurs," an assemblage of Cretaceous-Paleogene longirostrine crocodylians from Europe and North America. The position of "thoracosaurs" varies from one study to the next, from being the sister taxon of the extant Gavialis to being excluded from the crown group Crocodylia entirely. Despite these issues, "thoracosaurs" have been understudied, with many taxa suffering from incomplete or outdated descriptions and dubious taxonomic assignment. Here, we provide a comprehensive study of Thoracosaurus isorhynchus from Maastrichtian-Danian deposits of northwestern Europe. We present and describe new material from the type locality of T. isorhynchus. In addition, we redescribe and figure the lectotype and paralectotypes of the species, as well as the material from the Maastrichtian type area, the Netherlands. Moreover, comparison of T. isorhynchus with the type material of Thoracosaurus "scanicus" of the Danian of southern Sweden indicates that the latter might be a junior synonym of T. isorhynchus, suggesting the survival of this species across the Cretaceous-Paleogene boundary. An array of phylogenetic analyses points to a close relationship between T. isorhynchus and the Cenomanian Portugalosuchus azenhae. This implies an early emergence of "thoracosaurs" and causes extensive ghost lineages within Gavialoidea, highlighting the stratigraphic inconsistency of this group and a need for a thorough revision of other "thoracosaurs."

Raoellidae are small artiodactyls from the Indian subcontinent closely related to stem cetaceans. They bring crucial information to understand the early phase of the land-to-water transition in Cetacea. If they are considered to be partly aquatic, the question of their dietary habits remains partly understood due to their "transitional" morphology. Raoellidae are largely documented by their cheek teeth and getting a better knowledge of their anterior dentition constitutes an additional proxy to discuss their feeding habits. In this work, we document the anterior dentition of Indohyus indirae from an unprecedented sample of in situ and isolated teeth from the locality of East Aiji-2 in the Kalakot area (Rajouri district, India). We propose identification criteria for upper and lower incisors and canines in raoellids. Based on CT scan data, virtual reconstruction of in situ dentition, and identification of the isolated incisors and canines, we reconstruct a composite anterior dentition of Indohyus supported by the correspondence of wear facets between upper and lower teeth. This constitutes the first attempt at reconstruction of the anterior dentition of a raoellid. We show that the upper incisors are caniniform and very similar morphologically, whereas the lower incisors are pointed but remain incisiform and quite different from one another. We also describe noticeable intraspecific variation, at the level of upper canines, suggesting a potential sexual dimorphism in this species. Upper and lower incisors are recurved, with the upper incisor row arranged on a widely opened arch. Taken altogether the anterior dentition forms a grasping device, allowing the animal to capture and secure food, a characteristic shared with stem cetaceans. This would mark the first step towards the carnivorous diet in these peculiar artiodactyls.

Analyses of rock samples collected during recent fieldwork in the Ombilin Basin of west-central Sumatra, Indonesia yielded pollen data that constrain the age and depositional setting of associated plant macrofossil and vertebrate fossil-bearing units in the Sangkarewang and Sawahlunto formations. Articulated fish and plant fossils were recovered from bedding plane surfaces of fissile, laminated shales in the Sangkarewang Formation that are interpreted to have been deposited in an actively-subsiding, deep, anoxic lake. The overlying Talawi Member of the Sawahlunto Formation records stratigraphy consistent with deposition in a segue to marginal lacustrine marsh and poorly-drained paleosol settings. Interbedded carbonate mudstone / wackestone and lignitic claystone units in the basal Talawi Member preserve scattered, disarticulated fossils of fish, reptiles, an amphibian, and one mammal tooth. These beds grade into a heterolithic succession of fine-grained clastic rock, with coal interbeds likely deposited in a coastal alluvial setting. Marine influences in this interval are indicated by the nature of physical sedimentary structures in several zones, the presence of trace fossils such as Diplocraterion, Cylindrichnus and Teichichnus, and the occurrence of foraminiferal linings, dinocysts and other palynomorphs indicative of mangrove and back-mangrove settings. Palynological analysis indicates that the most probable age of the Sawahlunto Formation ranges from the middle to late Eocene, with a possible extension from the middle Eocene to the early Oligocene.

Cornus subgenus Cornus, also called cornelian cherries, is a relatively ancient clade of dogwoods with a complex biogeographic history. Their fossil record attests to a distribution in North America during the Late Cretaceous and Paleocene, whereas the earliest fossil record in Europe is dated as early as the Eocene. Here, we describe a new occurrence of cornelian cherries based on permineralized endocarps from the late Paleocene (ca. 58 Ma) land-mammal locality of Berru, in Northwest France. The 48 studied specimens possess characteristic cornelian cherry endocarp morphology with locules associated with a dorsal germination valve, no central vascularization, and the presence of numerous secretory cavities in the endocarp wall. In addition, the presence of (three)-four locules and a large apical depression strongly suggest affinities with the early Eocene species Cornus multilocularis from the London Clay Formation. This new occurrence expands the stratigraphic range of the species by approximately four to six million years and is the first unequivocal evidence of cornelian cherries in Europe during the Paleocene. The biogeographical history of cornelian cherries remains complex to explore because of its ancient distribution in the Cretaceous and a geographically and stratigraphically patchy Cenozoic record.

This study analyses the diverse types of bioerosion marks on the shells of two sea turtle specimens from the Lutetian (middle Eocene) of Belgium. The objective is to understand the physical stressors affecting these organisms in ancient marine environments and to identify the potential factors responsible for these changes. The first specimen, the holotype of Eochelone brabantica, presents multiple erosive anomalies on its costal plates. The second individual, corresponding to Puppigerus camperi, exhibits different types of shell deviations, also of an erosive character. The combination of macroscopic and imaging techniques (i.e., CT scanning and 3D surface scanning) allow us the precise observation and identification of the different alterations. Comparative analyses suggest several external factors as potential causes of the anomalies of the two specimens (i.e., invertebrate feeding traces and trauma). This detailed examination provides specific insights into the types and causes of shell alterations in these Eocene turtles, offering a clearer understanding of their interactions in the marine ecosystem in which they lived.

Marine sedimentary rocks of the late Eocene Pagat Member of the Tanjung Formation in the Asem Asem Basin near Satui, Kalimantan, provide an important geological archive for understanding the paleontological evolution of southern Kalimantan (Indonesian Borneo) in the interval leading up the development of the Central Indo-Pacific marine biodiversity hotspot. In this paper, we describe a moderately diverse assemblage of marine invertebrates within a sedimentological and stratigraphical context. In the studied section, the Pagat Member of the Tanjung Formation records an interval of overall marine transgression and chronicles a transition from the marginal marine and continental siliciclastic succession in the underlying Tambak Member to the carbonate platform succession in the overlying Berai Formation. The lower part of the Pagat Member contains heterolithic interbedded siliciclastic sandstone and glauconitic shale, with thin bioclastic floatstone and bioclastic rudstone beds. This segues into a calcareous shale succession with common foraminiferal packstone/rudstone lenses interpreted as low-relief biostromes. A diverse trace fossil assemblage occurs primarily in a muddy/glauconitic sandstone, sandy mudstone, and bioclastic packstone/rudstone succession, constraining the depositional setting to a mid-ramp/mid to distal continental shelf setting below fair-weather wave base but above storm wave base. Each biostrome rests upon a storm-generated ravinement surface characterized by a low-diversity Glossifungites or Trypanites trace fossil assemblage. The erosional surfaces were colonized by organisms that preferred stable substrates, including larger benthic foraminifera, solitary corals, oysters, and serpulid annelid worms. The biostromes comprised islands of high marine biodiversity on the mud-dominated Pagat coastline. Together, the biostromes analyzed in this study contained 13 genera of symbiont-bearing larger benthic foraminifera, similar to 40 mollusk taxa, at least 5 brachyuran decapod genera, and 6 coral genera (Anthemiphyllia, Balanophyllia, Caryophyllia, Cycloseris, Trachyphyllia, and Trochocyathus), as well as a variety of bryozoans, serpulids, echinoids, and asterozoans. High foraminiferal and molluscan diversity, coupled with modest coral diversity, supports the hypothesis that the origin of the diverse tropical invertebrate faunas that characterize the modern Indo-Australian region may have occurred in the latest Eocene/earliest Oligocene.

Here we report on anguimorph lizards from the earliest Eocene (MP 7) of the Dormaal locality in Belgium, from the time of the warmest global climate of the past 66 million years. Several clades can be identified in this site: Glyptosauridae, Varanidae, and Palaeovaranidae. Our study focuses on glyptosaurid specimens previously reported from the site, some of which had been provisionally described as a new species,?Placosaurus ragei, and some assigned to an unnamed Placosauriops-like 'melanosaurine'. Our study presents data on new material, including an almost complete glyptosaurine frontal that has enabled us to assign much of the previously described material to a single genus and species. The specimens that had been assigned to both ?P ragei and the 'melanosaurine' share apomorphies (flat osteoderms and chevron-shaped osteoderms) with Gaultia, a glyptosaurid previously known from the earliest Eocene of Wyoming, USA. The Dormaal material represents the first record of this genus outside North America. In fact, the only potential evidence of the occurrence of 'Melanosaurinae' in Dormaal might be a single isolated vertebra described here. Here we also describe previously unfigured material of Saniwa and palaeovaranids from Dormaal. The presence of previously reported helodermatids cannot be supported in this Belgian site.

The Messel Pit is a Konservat-Lagerstätte in Germany, representing the deposits of a latest early to earliest middle Eocene maar lake, and one of the first palaeontological sites to be included on the list of UNESCO World Heritage Sites. One aspect of Messel that makes it so extraordinary is that its sediments are rich in different fossilised organisms – microfossils, plants, fungi, invertebrate animals and vertebrates – that are rarely preserved together. We present an updated list of all taxa, named or not, that have been documented at Messel, comprising 1409 taxa, which represent a smaller but inexactly known number of biological species. The taxonomic list of Labandeira and Dunne (2014) contains serious deficiencies and should not be used uncritically. Furthermore, we compiled specimen lists of all Messel amphibians, reptiles and mammals known to us. In all, our analyses incorporate data from 32 public collections and some 20 private collections. We apply modern biodiversity-theoretic techniques to ascertain how species richness tracks sampling, to estimate what is the minimum asymptotic species richness, and to project how long it will take to sample a given proportion of that minimum richness. Plant and insect diversity is currently less well investigated than vertebrate diversity. Completeness of sampling in aquatic and semiaquatic, followed by volant, vertebrates is higher than in terrestrial vertebrates. Current excavation rates are one-half to two-thirds lower than in the recent past, leading to much higher estimates of the future excavation effort required to sample species richness more completely, should these rates be maintained. Species richness at Messel, which represents a lake within a paratropical forest near the end of the Early Eocene Climate Optimum, was generally higher than in comparable parts of Central Europe today but lower than in present-day Neotropical biotopes. There is no evidence that the Eocene Messel ecosystem was a “tropical rainforest.”

Eosuchus lerichei is a gavialoid crocodylian from late Paleocene marine deposits of northwestern Europe, known from a skull and lower jaws, as well as postcrania. Its sister taxon relationship with the approximately contemporaneous species Eosuchus minor from the east coast of the USA has been explained through transoceanic dispersal, indicating a capability for salt excretion that is absent in extant gavialoids. However, there is currently no anatomical evidence to support marine adaptation in extinct gavialoids. Furthermore, the placement of Eosuchus within Gavialoidea is labile, with some analyses supporting affinities with the Late Cretaceous to early Paleogene "thoracosaurs." Here we present novel data on the internal and external anatomy of the skull of E. lerichei that enables a revised diagnosis, with 6 autapormorphies identified for the genus and 10 features that enable differentiation of the species from Eosuchus minor. Our phylogenetic analyses recover Eosuchus as an early diverging gavialid gavialoid that is not part of the "thoracosaur" group. In addition to thickened semi-circular canal walls of the endosseous labyrinth and paratympanic sinus reduction, we identify potential osteological correlates for salt glands in the internal surface of the prefrontal and lacrimal bones of E. lerichei. These salt glands potentially provide anatomical evidence for the capability of transoceanic dispersal within Eosuchus, and we also identify them in the Late Cretaceous "thoracosaur" Portugalosuchus. Given that the earliest diverging and stratigraphically oldest gavialoids either have evidence for a nasal salt gland and/or have been recovered from marine deposits, this suggests the capacity for salt excretion might be ancestral for Gavialoidea. Mapping osteological and geological evidence for marine adaptation onto a phylogeny indicates that there was probably more than one independent loss/reduction in the capacity for salt excretion in gavialoids.

Raoellid mammals are small artiodactyls from the Eocene of Asia, hypothesized to be closely related to stem Cetacea. Knowledge of the cranial and dental morphology of Raoellidae comes mostly from one species, Indohyus indirae. Here we describe new material of another raoellid genus, Khirtharia, based on material retrieved from the Kalakot area, Jammu and Kashmir. This new material, comprising an almost complete, lightly deformed cranium and a partial snout with associated partial mandible, greatly adds to our knowledge of raoellid morphology. It highlights the similarity of cranial characters with Indohyus, such as a long snout with raptorial incisors, a thick and narrow supraorbital region, a strong postorbital constriction, a triangular shaped braincase, and a thickened medial wall to the auditory bulla (involucrum). The new specimen is similar to Indohyus cranially but differs dentally in being more bunodont. The presence of these traits in two different raoellid genera suggests they may be present more broadly across Raoellidae. These characters are also observed in early cetaceans, highlighting the need to investigate their phylogenetic impact. Some cranial features support aquatic habits of members of this family.

New material of the small raoellid artiodactyl Metkatius kashmiriensis is reported from the middle Eocene of the Upper Subathu Formation in the Kalakot area, Jammu and Kashmir, northwest Himalaya, India. The fossil material consists of numerous mandibular and maxillary fragments and isolated teeth, mainly belonging to juvenile specimens. It documents the poorly known dental morphology of M. kashmiriensis and provides an overview of its intraspecific variation, allowing to redefine its diagnosis. M. kashmiriensis is characterized by a particularly small size compared with other raoellid species, and by bunodont molars with moderately marked transverse lophs. The M/1-2 are much longer than wide and display characters similar to those of Rajouria gunnelli, such as the presence of a small paraconid and a mesial mesiostylid. The P/4 bears distally a small hypoconid, which appears to be unique in Raoellidae. The description of the new material also allows to document the poorly known morphology of the deciduous teeth of raoellids. The DP2/ is reported for the first time, and the DP/4 of M. kashmiriensis shows a morphology different from that of Indohyus, with the absence of mesial basin anterior to the paraconid and the primoconid. Contrary to what has recently been proposed, these results confirm that M. kashmiriensis is a valid species and not a synonym of Indohyus indirae, and highlight the great morphological diversity present within the Raoellidae during the middle Eocene in the Indian subcontinent. (c) 2024 Elsevier Masson SAS. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

INTRODUCTION:Raoellidae are small artiodactyls retrieved from the middle Eocene of Asia (ca. -47 Ma) and closely related to stem Cetacea. Morphological observations of their endocranial structures allow for outlining some of the early steps of the evolutionary history of the cetacean brain. The external features of the brain and associated sinuses of Raoellidae are so far only documented by the virtual reconstruction of the endocast based on specimens of the species Indohyus indirae. These specimens are however too deformed to fully access the external morphology, surface area, and volume measurements of the brain. METHODS:We bring here new elements to the picture of the raoellid brain by an investigation of the internal structures of an exceptionally well-preserved cranium collected from the Kalakot area (Jammu and Kashmir, India) referred to the species Khirtharia inflata. Micro-CT scan investigation and virtual reconstruction of the endocast and associated sinuses of this specimen provide crucial additional data about the morphological diversity within Raoellidae as well as reliable linear, surfaces, and volumes measurements, allowing for quantitative studies. RESULTS:We show that, like I. indirae, the brain of K. inflata exhibits a mosaic of features observed in earliest artiodactyls: a small neocortex with simple folding pattern, widely exposed midbrain, and relatively long cerebellum. But, like Indohyus, the brain of Khirtharia shows unique derived characters also observed in stem cetaceans: narrow elongated olfactory bulbs and peduncles, posterior location of the braincase in the cranium, and complex network of blood vessels around the cerebellum. The volume of the brain relative to body mass of K. inflata is markedly small when compared to other early artiodactyls. CONCLUSION:We show here that cetaceans that nowadays have the second biggest brain after humans derive from a group of animals that had a lower-than-average expected brain size. This is probably a side effect of the adaptation to aquatic life. Conversely, this very small brain size relative to body mass might be another line of evidence supporting the aquatic habits in raoellids.

In this work, we digitally restore the snout of the raoellid Khirtharia inflata from the Kalakot area (Rajouri District, Jammu & Kashmir, India).Raoellids are small, semiaquatic ungulates closely related to cetaceans.The specimen is fairly complete and preserves left and right maxillae, left premaxilla, and part of the anterior and jugal dentition.The digital restoration of this quite complete but deformed specimen of Khirtharia inflata is a welcome addition to the data available for raoellids and will be used to further the understanding of the origins of cetaceans.