The Miocene primate Pliobates is a pliopithecoid.

The systematic status of the small-bodied catarrhine primate Pliobates cataloniae, from the Miocene (11.6 Ma) of Spain, is controversial because it displays a mosaic of primitive and derived features compared with extant hominoids (apes and humans). Cladistic analyses have recovered Pliobates as either a stem hominoid or as a pliopithecoid stem catarrhine (i.e., preceding the cercopithecoid-hominoid divergence). Here, we describe additional dental remains of P. cataloniae from another locality that display unambiguous synapomorphies of crouzeliid pliopithecoids. Our cladistic analyses support a close phylogenetic link with poorly-known small crouzeliids from Europe based on (cranio)dental characters but recover pliopithecoids as stem hominoids when postcranial characters are included. We conclude that Pliobates is a derived stem catarrhine that shows postcranial convergences with modern apes in the elbow and wrist joints-thus clarifying pliopithecoid evolution and illustrating the plausibility of independent acquisition of postcranial similarities between hylobatids and hominids.

The reconstructed cranium of Pierolapithecus and the evolution of the great ape face.

Pierolapithecus catalaunicus (~12 million years ago, northeastern Spain) is key to understanding the mosaic nature of hominid (great ape and human) evolution. Notably, its skeleton indicates that an orthograde (upright) body plan preceded suspensory adaptations in hominid evolution. However, there is ongoing debate about this species, partly because the sole known cranium, preserving a nearly complete face, suffers from taphonomic damage. We 1) carried out a micro computerized tomography (CT) based virtual reconstruction of the Pierolapithecus cranium, 2) assessed its morphological affinities using a series of two-dimensional (2D) and three-dimensional (3D) morphometric analyses, and 3) modeled the evolution of key aspects of ape face form. The reconstruction clarifies many aspects of the facial morphology of Pierolapithecus. Our results indicate that it is most similar to great apes (fossil and extant) in overall face shape and size and is morphologically distinct from other Middle Miocene apes. Crown great apes can be distinguished from other taxa in several facial metrics (e.g., low midfacial prognathism, relatively tall faces) and only some of these features are found in Pierolapithecus, which is most consistent with a stem (basal) hominid position. The inferred morphology at all ancestral nodes within the hominoid (ape and human) tree is closer to great apes than to hylobatids (gibbons and siamangs), which are convergent with other smaller anthropoids. Our analyses support a hominid ancestor that was distinct from all extant and fossil hominids in overall facial shape and shared many features with Pierolapithecus. This reconstructed ancestral morphotype represents a testable hypothesis that can be reevaluated as new fossils are discovered.

Insular giant leporid matured later than predicted by scaling.

The island syndrome describes morphological, behavioral, and life history traits that evolve in parallel in endemic insular organisms. A basic axiom of the island syndrome is that insular endemics slow down their pace of life. Although this is already confirmed for insular dwarfs, a slow life history in giants may not be adaptive, but merely a consequence of increasing body size. We tested this question in the fossil insular giant leporid Nuralagus rex. Using bone histology, we constructed both a continental extant taxon model derived from experimentally fluorochrome-labeled Lepus europaeus to calibrate life history events, and a growth model for the insular taxon. N. rex grew extremely slowly and delayed maturity well beyond predictions from continental phylogenetically corrected scaling models. Our results support the life history axiom of the island syndrome as generality for insular mammals, regardless of whether they have evolved into dwarfs or giants.

Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant.

The 1-m-tall dwarf elephant Palaeoloxodon falconeri from the Pleistocene of Sicily (Italy) is an extreme example of insular dwarfism and epitomizes the Island Rule. Based on scaling of life-history (LH) traits with body mass, P. falconeri is widely considered to be 'r-selected' by truncation of the growth period, associated with an early onset of reproduction and an abbreviated lifespan. These conjectures are, however, at odds with predictions from LH models for adaptive shifts in body size on islands. To settle the LH strategy of P. falconeri, we used bone, molar, and tusk histology to infer growth rates, age at first reproduction, and longevity. Our results from all approaches are congruent and provide evidence that the insular dwarf elephant grew at very slow rates over an extended period; attained maturity at the age of 15 years; and had a minimum lifespan of 68 years. This surpasses not only the values predicted from body mass but even those of both its giant sister taxon (P. antiquus) and its large mainland cousin (L. africana). The suite of LH traits of P. falconeri is consistent with the LH data hitherto inferred for other dwarfed insular mammals. P. falconeri, thus, not only epitomizes the Island Rule but it can also be viewed as a paradigm of evolutionary change towards a slow LH that accompanies the process of dwarfing in insular mammals.

Comparative anatomy of the carotid canal in the Miocene small-bodied catarrhine Pliobates cataloniae.

The small-bodied Miocene catarrhine Pliobates cataloniae (11.6 Ma, Spain) displays a mosaic of catarrhine symplesiomorphies and hominoid synapomorphies that hinders deciphering its phylogenetic relationships. Based on cladistic analyses, it has been interpreted as a stem hominoid or as a pliopithecoid. Intriguingly, the carotid canal orientation of Pliobates was originally described as hylobatid-like. The variation in carotid canal morphology among anthropoid clades shown in previous studies suggests that this structure might be phylogenetically informative. However, its potential for phylogenetic reconstruction among extinct catarrhines remains largely unexplored. Here we quantify the orientation, proportions, and course of the carotid canal in Pliobates, extant anthropoids and other Miocene catarrhines (Epipliopithecus, Victoriapithecus, and Ekembo) using three-dimensional morphometric techniques. We also compute phylogenetic signal and reconstruct the ancestral carotid canal course for main anthropoid clades. Our results reveal that carotid canal morphology embeds strong phylogenetic signal but mostly discriminates between platyrrhines and catarrhines, with an extensive overlap among extant catarrhine families. The analyzed extinct taxa display a quite similar carotid canal morphology more closely resembling that of extant catarrhines. Nevertheless, our results for Pliobates highlight some differences compared with the pliopithecid Epipliopithecus, which displays a somewhat more platyrrhine-like morphology. In contrast, Pliobates appears as derived toward the modern catarrhine condition as the stem cercopithecid Victoriapithecus and the stem hominoid Ekembo, which more closely resemble one another. Moreover, Pliobates appears somewhat derived toward the reconstructed ancestral hominoid morphotype, being more similar than other Miocene catarrhines to the condition of great apes and the hylobatid Symphalangus. Overall, our results rule out previously noted similarities in carotid canal morphology between Pliobates and hylobatids, but do not show particular similarities with pliopithecoids either-as opposed to extant and other extinct catarrhines. Additional analyses will be required to clarify the phylogenetic relationships of Pliobates, particularly given its dental similarities with dendropithecids.

A proximal radius of Barberapithecus huerzeleri from Castell de Barberà: Implications for locomotor diversity among pliopithecoids.

Pliopithecoids are a diverse group of Miocene catarrhine primates from Eurasia. Their positional behavior is still unknown, and many species are known exclusively from dentognathic remains. Here, we describe a proximal radius (IPS66267) from the late Miocene of Castell de Barberà (Vallès-Penedès Basin, NE Iberian Peninsula) that represents the first postcranial specimen of the pliopithecoid Barberapithecus huerzeleri. A body mass estimate based on the radius is compared with dental estimates, and its morphology is compared with that of extant and fossil anthropoids by qualitative means as well as by landmark-based three-dimensional geometric morphometrics. The estimated body mass of ∼5 kg for IPS66267 closely matches the dental estimates for the (female) holotype, thereby discounting an alternative attribution to the large-bodied hominoid recorded at Castell de Barberà. In multiple features (oval and moderately tilted head with a pronounced lateral lip and a restricted articular area for the capitulum; proximodistally expanded proximal radioulnar joint; and short, robust, and anteroposteriorly compressed neck), the specimen differs from hominoids and resembles instead extant nonateline monkeys and stem catarrhines. The results of the morphometric analysis further indicate that the Barberapithecus proximal radius shows closer similarities with nonsuspensory arboreal cercopithecoids and the dendropithecid Simiolus. From a locomotor viewpoint, the radius of Barberapithecus lacks most of the features functionally related to climbing and/or suspensory behaviors and displays instead a proximal radioulnar joint that would have been particularly stable under pronation. On the other hand, the Barberapithecus radius differs from other stem catarrhines in the less anteroposteriorly compressed and less tilted radial head with a deeper capitular fovea, suggesting a somewhat enhanced mobility at the elbow joint. We conclude that pronograde arboreal quadrupedalism was the main component of the locomotor repertoire of Barberapithecus but that, similar to other crouzeliids, it might have displayed better climbing abilities than pliopithecids.

Fossil apes and human evolution.

Humans diverged from apes (chimpanzees, specifically) toward the end of the Miocene ~9.3 million to 6.5 million years ago. Understanding the origins of the human lineage (hominins) requires reconstructing the morphology, behavior, and environment of the chimpanzee-human last common ancestor. Modern hominoids (that is, humans and apes) share multiple features (for example, an orthograde body plan facilitating upright positional behaviors). However, the fossil record indicates that living hominoids constitute narrow representatives of an ancient radiation of more widely distributed, diverse species, none of which exhibit the entire suite of locomotor adaptations present in the extant relatives. Hence, some modern ape similarities might have evolved in parallel in response to similar selection pressures. Current evidence suggests that hominins originated in Africa from Miocene ape ancestors unlike any living species.

A comparative analysis of the vestibular apparatus in Epipliopithecus vindobonensis: Phylogenetic implications.

Pliopithecoids are an extinct group of catarrhine primates from the Miocene of Eurasia. More than 50 years ago, they were linked to hylobatids due to some morphological similarities, but most subsequent studies have supported a stem catarrhine status, due to the retention of multiple plesiomorphic features (e.g., the ectotympanic morphology) relative to crown catarrhines. More recently, some morphological similarities to hominoids have been noted, raising the question of whether they could be stem members of this clade. To re-evaluate these competing hypotheses, we examine the morphology of the semicircular canals of the bony labyrinth of the middle Miocene pliopithecid Epipliopithecus vindobonensis. The semicircular canals are suitable to test between these hypotheses because (1) they have been shown to embed strong phylogenetic signal and reliably discriminate among major clades; (2) several potential hominoid synapomorphies have been identified previously in the semicircular canals; and (3) semicircular canal morphology has not been previously described for any pliopithecoid. We use a deformation-based (landmark-free) three-dimensional geometric morphometric approach to compare Epipliopithecus with a broad primate sample of extant and extinct anthropoids. We quantify similarities in semicircular canal morphology using multivariate analyses, reconstruct ancestral morphotypes by means of a phylomorphospace approach, and identify catarrhine and hominoid synapomorphies based on discrete characters. Epipliopithecus semicircular canal morphology most closely resembles that of platyrrhines and Aegyptopithecus due to the retention of multiple anthropoid symplesiomorphies. However, Epipliopithecus is most parsimoniously interpreted as a stem catarrhine more derived than Aegyptopithecus due to the possession of a crown catarrhine synapomorphy (i.e., the rounded anterior canal), combined with the lack of other catarrhine and any hominoid synapomorphies. Some similarities with hylobatids and atelids are interpreted as homoplasies likely related to positional behavior. The semicircular canal morphology of Epipliopithecus thus supports the common view that pliopithecoids are stem catarrhines.

Reassessment of the phylogenetic relationships of the late Miocene apes Hispanopithecus and Rudapithecus based on vestibular morphology.

Late Miocene great apes are key to reconstructing the ancestral morphotype from which earliest hominins evolved. Despite consensus that the late Miocene dryopith great apes Hispanopithecus laietanus (Spain) and Rudapithecus hungaricus (Hungary) are closely related (Hominidae), ongoing debate on their phylogenetic relationships with extant apes (stem hominids, hominines, or pongines) complicates our understanding of great ape and human evolution. To clarify this question, we rely on the morphology of the inner ear semicircular canals, which has been shown to be phylogenetically informative. Based on microcomputed tomography scans, we describe the vestibular morphology of Hispanopithecus and Rudapithecus, and compare them with extant hominoids using landmark-free deformation-based three-dimensional geometric morphometric analyses. We also provide critical evidence about the evolutionary patterns of the vestibular apparatus in living and fossil hominoids under different phylogenetic assumptions for dryopiths. Our results are consistent with the distinction of Rudapithecus and Hispanopithecus at the genus rank, and further support their allocation to the Hominidae based on their derived semicircular canal volumetric proportions. Compared with extant hominids, the vestibular morphology of Hispanopithecus and Rudapithecus most closely resembles that of African apes, and differs from the derived condition of orangutans. However, the vestibular morphologies reconstructed for the last common ancestors of dryopiths, crown hominines, and crown hominids are very similar, indicating that hominines are plesiomorphic in this regard. Therefore, our results do not conclusively favor a hominine or stem hominid status for the investigated dryopiths.

The evolution of the vestibular apparatus in apes and humans.

Phylogenetic relationships among extinct hominoids (apes and humans) are controversial due to pervasive homoplasy and the incompleteness of the fossil record. The bony labyrinth might contribute to this debate, as it displays strong phylogenetic signal among other mammals. However, the potential of the vestibular apparatus for phylogenetic reconstruction among fossil apes remains understudied. Here we test and quantify the phylogenetic signal embedded in the vestibular morphology of extant anthropoids (monkeys, apes and humans) and two extinct apes (Oreopithecus and Australopithecus) as captured by a deformation-based 3D geometric morphometric analysis. We also reconstruct the ancestral morphology of various hominoid clades based on phylogenetically-informed maximum likelihood methods. Besides revealing strong phylogenetic signal in the vestibule and enabling the proposal of potential synapomorphies for various hominoid clades, our results confirm the relevance of vestibular morphology for addressing the controversial phylogenetic relationships of fossil apes.

Humans, gorillas, chimpanzees, orangutans and gibbons all belong to a group known as the hominoids. This 'superfamily' also includes the immediate ancestors and close relatives of these species, however in many instances the evolutionary relationships between these extinct ape species remain controversial. While DNA can help evolutionary biologists to work out how living species are related to one another, fossils are typically the principle source of information for extinct species. Inferring evolutionary relationships from fossils must be done with caution, but the bony cavity that houses the inner ear ­ which is involved in balance and hearing and fairly common in the fossil record ­ has proven useful for tracing the evolution of certain groups of mammals. However, no one had previously looked to see if this structure could give insights into the evolutionary relatedness among living and extinct hominoids. Urciuoli et al. have now used a 3D imaging technique to capture the complex shapes of the inner ear cavities of 27 species of monkeys and apes, including humans and two extinct apes (Oreopithecus and Australopithecus). The results confirmed that the shape of these structures most closely reflected the evolutionary relationships between the species and not, for example, how the animals moved. Urciuoli et al. went on to identify features of these bony chambers that were shared within several hominoid groups, and to estimate what the inner ears of the ancestors of these groups might have looked like. The results for Australopithecus, for example, were consistent with it being most closely related to modern humans than other apes, while those for the enigmatic Oreopithecus supported the view that it was a much older species of ape that converged in some respects with other apes still alive today. The findings highlight the potential of the inner ear for reconstructing the early branches of our family tree. They also offer the prospect of refining the controversial evolutionary relationships within the impressive diversity of extinct ape species.

First navicular remains of a European adapiform (Anchomomys frontanyensis) from the Middle Eocene of the Eastern Pyrenees (Catalonia, Spain): implications for early primate locomotor behavior and navicular evolution.

We describe the first known navicular bones for an Eocene euprimate from Europe and assess their implications for early patterns of locomotor evolution in primates. Recovered from the fossil site of Sant Jaume de Frontanyà-3C (Barcelona, Spain), the naviculars are attributed to Anchomomys frontanyensis. The small size of A. frontanyensis allows us to consider behavioral implications of comparisons with omomyiforms, regardless of allometric sources of navicular variation. Researchers usually consider omomyiforms to be more prone to leaping than contemporaneous adapiforms partly because of the more pronounced elongation of omomyiform tarsal elements. However, A. frontanyensis differs from other adapiforms and is similar to some omomyiforms in its more elongated navicular proportions. Although this might raise questions about attribution of these naviculars to A. frontanyensis, the elements exhibit clear strepsirrhine affinities leaving little doubt about the attribution: the bones' mesocuneiform facets contact their cuboid facets. We further propose that this strepsirrhine-specific feature in A. frontanyensis and other adapiforms reflects use of more inverted foot postures and potentially smaller substrates than sympatric omomyiforms that lack it. Thus substrate differences may have influenced niche partitioning in Eocene euprimate communities along with differences in locomotor agility. As previous studies on the astragalus and the calcaneus have suggested, this study on the navicular is consistent with the hypothesis that the locomotor mode of A. frontanyensis was similar to that of extant cheirogaleids, especially species of Microcebus and Mirza.

Insights into the lower torso in late Miocene hominoid Oreopithecus bambolii.

Oreopithecus bambolii (8.3-6.7 million years old) is the latest known hominoid from Europe, dating to approximately the divergence time of the Pan-hominin lineages. Despite being the most complete nonhominin hominoid in the fossil record, the O. bambolii skeleton IGF 11778 has been, for decades, at the center of intense debate regarding the species' locomotor behavior, phylogenetic position, insular paleoenvironment, and utility as a model for early hominin anatomy. Here we investigate features of the IGF 11778 pelvis and lumbar region based on torso preparations and supplemented by other O. bambolii material. We correct several crucial interpretations relating to the IGF 11778 anterior inferior iliac spine and lumbar vertebrae structure and identifications. We find that features of the early hominin Ardipithecus ramidus torso that are argued to have permitted both lordosis and pelvic stabilization during upright walking are not present in O. bambolii However, O. bambolii also lacks the complete reorganization for torso stiffness seen in extant great apes (i.e., living members of the Hominidae), and is more similar to large hylobatids in certain aspects of torso form. We discuss the major implications of the O. bambolii lower torso anatomy and how O. bambolii informs scenarios of hominoid evolution.

Femoral neck cortical bone distribution of dryopithecin apes and the evolution of hominid locomotion.

Only a few postcranial remains have been assigned to the Miocene great ape Dryopithecus fontani, leading to uncertainties in the reconstruction of its overall body plan and positional behavior. Here we shed light on the locomotor repertoire of this species through the study of the femoral neck cortical bone (FNCB) distribution of IPS41724, a partial proximal femur from the Abocador de Can Mata locality ACM/C3-Az (11.9 Ma, middle Miocene; Vallès-Penedès Basin, Spain) attributed to this taxon. This specimen was scanned through computed tomography to measure the superior (SUP) and inferior (INF) cortical thicknesses at the middle and the base of the femoral neck. Measurements were compared with a sample of extant primates and the femur IPS18800.29 from the younger great ape Hispanopithecus laietanus from Can Llobateres 2 (9.6 Ma, late Miocene; Vallès-Penedès Basin), previously shown to display a homogeneous FNCB distribution at the midneck section coupled with postcranial adaptations to below-branch suspensory behaviors. Our analyses indicate an asymmetric FNCB distribution for IPS41724 (SUP/INF index = âˆ¼0.4 at the midneck and base of the neck sections), comparable with that of quadrupedal primates and bipedal hominins (including early australopiths), but contrasting with the homogeneous FNCB distribution of Hispanopithecus and extant great apes. An asymmetrical FNCB distribution has been associated with stereotyped loads at the hip joint (as in both quadrupedal and bipedal taxa). Our results therefore support a significant quadrupedal component of the positional behavior of Dryopithecus, thus strengthening the argument that plesiomorphic generalized quadrupedalism was still a major locomotor behavior for Miocene great apes. If that were the case, it could have deep implications for the origins of hominin bipedalism.

Bio- and magnetostratigraphic correlation of the Miocene primate-bearing site of Castell de Barberà to the earliest Vallesian.

Castell de Barberà, located in the Vallès-Penedès Basin (NE Iberian Peninsula), is one of the few European sites where pliopithecoids (Barberapithecus) and hominoids (cf. Dryopithecus) co-occur. The dating of this Miocene site has proven controversial. A latest Aragonian (MN7+8, ca. 11.88-11.18 Ma) age was long accepted by most authors, despite subsequent reports of hipparionin remains that signaled a Vallesian age. On the latter basis, Castell de Barberà was recently correlated to the early Vallesian (MN9, ca. 11.18-10.3 Ma) on tentative grounds. Uncertainties about the provenance of the Hippotherium material and the lack of magnetostratigraphic data precluded more accurate dating. After decades of inactivity, fieldwork was resumed in 2014-2015 at Castell de Barberà, including the original layer (CB-D) that previously delivered most of the fossils. Here we report magnetostratigraphic results for the original outcrop and another nearby section. Our results indicate that CB-D is located in a normal polarity magnetozone in the middle of a short (∼20 m-thick) stratigraphic section. The composite magnetostratigraphic section (∼50 m) has as many as four to six magnetozones. These multiple reversals, coupled with the in situ recovery of a Hippotherium humerus from CB-D in 2015, make it unlikely that any of the sampled normal polarity magnetozones correlate with the long normal polarity subchron C5n.2n (11.056-9.984 Ma), which is characteristic of the early Vallesian. Our results support instead a correlation of CB-D with C5r.1n (11.188-11.146 Ma), where the Aragonian/Vallesian boundary is situated, and therefore indicate an earliest Vallesian age of ∼11.2 Ma for Castell de Barberà. Our results settle the longstanding debate about the Aragonian vs. Vallesian age of this site, which appears roughly coeval with the Creu de Conill 20 locality (11.18 Ma), where hipparionins are first recorded in the Vallès-Penedès Basin.

The primate remains from Roc de Santa (Late Eocene, NE Spain) revisited: New taxonomic allocation.

The scarce primate remains from the late Eocene locality of Roc de Santa (Central Pyrenees, NE Spain) were first documented in 1975. This material included a mandibular fragment with P3-M2 and a maxillary fragment with P3-M3 assigned to Adapis magnus (later transferred to the genus Leptadapis), and an isolated M3 attributed to Necrolemur antiquus. However, these specimens were never described in detail. We have thoroughly studied these specimens, with the exception of the mandibular fragment, which has been lost. The maxillary fragment is much smaller than in Leptadapis magnus and shows clear morphological differences from that species; this specimen is assigned to Microchoerus hookeri. Similarly, the isolated M3 resembles that of M. hookeri in size and morphology, and can therefore be attributed to this taxon. In addition, we describe an upper incisor never reported previously, which can also be allocated to M. hookeri, representing the first description of this tooth for the species. Therefore, we conclude that the previous taxonomic determinations were mistaken and all the available primate specimens from Roc de Santa can be confidently assigned to the species M. hookeri, previously described from the same-age localities of Sossís, Spain, and Eclépens-B, Switzerland.

Can Pallars i Llobateres: A new hominoid-bearing locality from the late Miocene of the Vallès-Penedès Basin (NE Iberian Peninsula).

In the Iberian Peninsula, Miocene apes (Hominoidea) are generally rare and mostly restricted to the Vallès-Penedès Basin. Here we report a new hominoid maxillary fragment with M2 from this basin. It was surface-collected in March 2017 from the site of Can Pallars i Llobateres (CPL, Sant Quirze del Vallès), where fossil apes had not been previously recorded. The locality of provenance (CPL-M), which has delivered no further fossil remains, is located very close (ca. 50 m) to previously known CPL outcrops, and not very far (ca. 500 m in NW direction) from the classical hominoid-bearing locality of Can Poncic 1. Here we describe the new fossil and, based on the size and proportions of the M2, justify its taxonomic attribution to Hispanopithecus cf. laietanus, a species previously recorded from several Vallesian sites of the Vallès-Penedès Basin. Based on the associated mammalian fauna from CPL, we also provide a biochronological dating and a paleoenvironmental reconstruction for the site. The associated fauna enables an unambiguous correlation to the Cricetulodon hartenbergeri - Progonomys hispanicus interval local subzone, with an estimated age of 9.98-9.73 Ma (late Vallesian, MN10). Therefore, CPL-M is roughly coeval with the Hispanopithecus laietanus-bearing localities of Can Llobateres 1 and Can Feu 1, and minimally older than those of La Tarumba 1 and Can Llobateres 2. In contrast, CPL-M is younger than the early Vallesian (MN9) localities of Can Poncic 1 (the type locality of Hispanopithecus crusafonti) as well as Polinyà 2 (Gabarró) and Estació Depuradora d'Aigües Residuals-Riu Ripoll 13, where Hispanopithecus sp. is recorded. The associated fauna from CPL indicates a densely forested and humid paleoenvironment with nearby freshwater. This supports the view that Hispanopithecus might have been restricted to dense wetland forests soon before its extinction during the late Vallesian, due to progressive climatic deterioration. Coupled with the existence of other fossiliferous outcrops in the area, this find is most promising for the prospect of discovering additional fossil hominoid remains in the future.

Neutron-based computed microtomography: Pliobates cataloniae and Barberapithecus huerzeleri as a test-case study.

OBJECTIVES: High-resolution imaging of fossils with X-ray computed microtomography (µCT) has become a very powerful tool in paleontological research. However, fossilized bone, embedding matrix, and dental tissues do not always provide a distinct structural signal with X-rays. We demonstrate the benefits of high-resolution neutron radiation in three different specimens showing problematic contrasts with X-ray µCT. MATERIALS AND METHODS: We compare neutron with X-ray µCT scans of fossils from two Miocene catarrhines from the Vallès-Penedès Basin: the cranium (IPS58443.1, holotype) of the putative stem hominoid Pliobates cataloniae, to discriminate between bone and matrix; and two lower molars (IPS1724n,o, holotype) of Barberapithecus huerzeleri, to discriminate among dental tissues. RESULTS: X-ray µCT scans of these specimens fail to retrieve any contrast between matrix/bone and enamel/dentine, whereas neutron µCT scans deliver high-contrast images, enabling a proper evaluation of the specimens' internal anatomy. DISCUSSION: Low bone/matrix intensity difference with X-ray µCT scans in IPS58443.1 is due to the extreme similarity in chemical composition between the matrix and the fossilized tissues, and the presence of high-density elements. In IPS1724, it is attributable to the convergence of enamel and dentine compositions during fossilization. On the contrary, neutron radiation returns very different contrasts for different isotopes of the same element and easily penetrates most metals. Neutron-based µCT scans therefore enable a correct definition of the bone/sediment and enamel/dentine interfaces, and hence a better segmentation of the images stack. We conclude that neutron radiation represents a successful alternative for high-resolution µCT of small-sized fossils that are problematic with X-rays.

New dental and postcranial material of Agerinia smithorum (Primates, Adapiformes) from the type locality Casa Retjo-1 (early Eocene, Iberian Peninsula).

New material attributed to Agerinia smithorum from Casa Retjo-1 (early Eocene, NE Iberian Peninsula), consisting of 13 isolated teeth and a fragment of calcaneus, is studied in this work. These fossils allow the first description of the calcaneus and the upper premolars for the genus Agerinia, as well as the first description of the P2 and M2 for A. smithorum. The newly recovered lower teeth are virtually identical to the holotype of A. smithorum and are clearly distinguishable from the other species of Agerinia. The upper teeth also show clear differences with Agerinia marandati. The morphology of the calcaneal remains reveals that A. smithorum practiced a moderately active arboreal quadrupedal mode of locomotion, showing less leaping proclivity than notharctines but more than asiadapids. All the morphological features observed in the described material reinforce the hypothesis of a single lineage consisting of the species A. smithorum, A. marandati, and Agerinia roselli. Furthermore, the phylogenetic analysis developed in this work, which incorporates the newly described remains of A. smithorum, maintains the position of Agerinia as closely related to sivaladapids and asiadapids.