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Endocranial casts are capable of capturing the general brain form in extinct mammals due to the high fidelity of the endocranial cavity and the brain in this clade. Camelids, the clade including extant camels, llamas, and alpacas, today display high levels of gyrification and brain complexity. The evolutionary history of the camelid brain has been described as involving unique neocortical growth dynamics which may have led to its current state. However, these inferences are based on their fossil endocast record from approximately ∼40 Mya (Eocene) to ∼11 Mya (Miocene), with a gap in this record for the last ∼10 million years. Here, we present the first descriptions of two camelid endocrania that document the recent history of the camelid brain: a new specimen of Palaeolama sp. from ∼1.2 Mya, and the plaster endocast of Camelops hesternus, a giant camelid from ∼44 to 11 Kya which possessed the largest brain (∼990 g) of all known camelids. We find that neocortical complexity evolved significantly between the Miocene and Pleistocene Epochs. Already ∼1.2 Mya the camelid brain presented morphologies previously known only in extant taxa, especially in the frontal and parietal regions, which may also be phylogenetic informative. The new fossil data indicate that during the Pleistocene, camelid brain dynamics experienced neocortical invagination into the sagittal sinus rather than evagination out of it, as observed in Eocene to Miocene taxa. [ABSTRACT FROM AUTHOR]

Domestication has led to many changes in domestic animal biology, including their anatomy. The shape of the inner ear, part of the mammalian ear, has been found particularly relevant for discriminating domesticated species, their hybrids or differentiating the wild and domestic populations of a single species. Here we assessed the use of the size and shape of the semicircular canals (SCC) of the inner ear as a marker of pig domestication. We studied a total of 63 petrosal bones belonging to wild boar (Sus scrofa, two populations) and domestic pigs (extensively and intensively reared specimens) that were µCT‐scanned and from which the size and the shape of the inner ear were quantified through geometric morphometrics, analyzing the 3D coordinates of 6 landmarks and 60 sliding semilandmarks localized on the SCC and the common crus. The domestic pigs have larger SCC than the wild boar from which they also strongly differ in shape (correct cross validation of 95.5%, confidence interval: 92.3%–98.1%). Strong shape differences were detected between the two populations of wild boar, as well as a sexual size dimorphism. All together the results highlight the taxonomic discriminant power of the SCC of the inner ear shape, and its relevance for domestication studies. RESEARCH HIGHLIGHTS: The semicircular canals (SCC) shape allow to discriminate wild boar and domestic pig with a correct cross validation of 95.5%Domestic pigs have larger SCC than the wild boar • Wild boar populations differ in their SCC shape not size.The shape of the semicircular canal of the inner ear can be used as a marker of domestication [ABSTRACT FROM AUTHOR]

This work describes an unparalleled sample of isolated fossil auditory ossicles of cainotheriid artiodactyls from the Paleogene karstic infillings of Dams (Tarn‐et‐Garonne, Quercy, France). This collection comprises a total of 18 mallei, 28 incudes and three stapedes. It allows the documentation of both intra‐ and interspecific variability of ossicular morphology within Cainotheriidae. We show that despite considerable intraspecific variability, the malleus, the incus and the stapes appear to be taxonomically informative at the Cainotheriidae scale. This work further provides the first description of a reconstructed ossicular chain of a terrestrial Paleogene artiodactyl species, found in a basicranium of the late Oligocene cainotheriine Caenomeryx filholi (Pech Desse locality). [ABSTRACT FROM AUTHOR]

Extant cetaceans are fully aquatic mammals with deep modifications of their sensory organs, notably of the sound perception pathway. Early diverging cetaceans, known as archaeocetes, show a diversity of morphologies of the petrotympanic complex and middle ear ossicles, documenting a variety of sound transmission mechanisms from a mostly terrestrial configuration to a fully aquatic layout. Protocetids are a paraphyletic assemblage of semi-aquatic archaeocetes known from the Eocene. The auditory region of these ‘transitional’ forms is only partly known. The middle Eocene locality of Kpogamé, Togo (46-43 Ma) has yielded abundant material of protocetid whales documenting the auditory region, including isolated bullae, one petrosal and a skull fragment preserving the petrotympanic complex. Detailed study of this material leads us to reassess the original taxonomic attribution of this material, first attributed to Togocetus traversei, and to recognize three different protocetid taxa on the basis of bullar and petrosal remains: ?Carolinacetus sp., Togocetus traversei and Protocetidae indeterminate (morphotype γ). Associating isolated petrosals or bullae with dental remains solely based on size criteria can be misleading and we show here that there is no correlation between the size of tympanic bulla and size of dental remains in protocetids. CT-scan investigation of the in situ petrotympanic complex reveals that Protocetidae retained a complete tympanic ring similar to that of terrestrial artiodactyls and that the involucrum could probably articulate with the medial side of the ventral surface of the petrosal. This bulla/petrosal articulation is absent in fully aquatic cetaceans. Finally, the close phylogenetic relationships between protocetids from Kpogamé and North American protocetids suggest successive dispersals of these non-fully aquatic archaeocetes from African coasts to North America. [ABSTRACT FROM AUTHOR]

Objectives: Innovations in brain structure and increase in brain size relative to body mass are key features of Primates evolutionary history. Surprisingly, the endocranial morphology of early Euprimates is still rather poorly known, and our understanding of early euprimate brain evolution (Eocene epoch) relies on a handful of specimens. Materials and Methods: In this article, we describe the endocranial cast of the tarsiiform Microchoerus erinaceus from the late Early Eocene of Perrière (Quercy fissure filling, France) based on a virtual reconstruction extracted from CT scan data of the endocranial cavity of the complete, undeformed specimen UM-PRR1771. Results: The endocast of M. erinaceus shows the derived features observed in other Euprimates (e.g. sylvian fissure and temporal lobe), with limited neocortical folding, and a telencephalic flexure comparable to that of extant primates. Discussion: Comparison with the endocasts of other available late Eocene primates shows that they already exhibited a variety of brain morphologies, highlighting the complex history of the external features of the primate brain, as early as the Eocene. M. erinaceus was a fruit and gum eater considered as nocturnal based on its orbit size. However, its brain showed small olfactory bulbs--smaller than in the coeval diurnal taxa Adapis parisiensis--and a neocorticalization similar to folivorous taxa. These observations contrast with patterns observed in primates today where nocturnal taxa have larger olfactory bulbs than diurnal taxa, and call into question a direct correlation between frugivory and neocorticalization increase in primates. [ABSTRACT FROM AUTHOR]

We describe the bony labyrinth morphology of the Eocene ‘archaic ungulate’Hyopsoduslepidus(Bridgerian, North America) reconstructed from micro computed tomography scan data. Comparisons with the inner ear of the Eocene early diverging artiodactylDiacodexisand perissodactylXenicohippusallow refining the picture of the ancestral inner ear morphology of Euungulates. These taxa are very close morphologically and mostly differ by slight differences in their semicircular canal angulations and profile. They all present a secondary crus and a low position of the plane of the lateral semicircular canal relative to the posterior semicircular canal. These two characters, considered as ancestral features for Theria, might be symplesiomorphies of Euungulata as well.HyopsodusandXenicohippusshare characters also observed in other basal Equoidea, which would support the close relationship between these two taxa previously proposed in the literature. A functional study of the cochlea ofHyopsodus lepidusis also realised to discuss its putative ability of using terrestrial echolocation previously proposed in the literature. The morphology of the cochlea ofHyopsodus lepidusdoes not indicate a specialisation to sophisticated echolocation such as observed today in microchiropteran bats. However, its estimated audible range of frequencies (208 Hz to 76.8 KHz) would be compatible with terrestrial echolocation. [ABSTRACT FROM AUTHOR]

Macroscelidea (elephant-shrews or sengis) are small insectivorous mammals restricted to Africa; they belong to the super-cohort Afrotheria along with other insectivorans (aardvarks, tenrecs and golden moles) and ungulates (elephants, sea cows and hyraxes). Though their fossil record extends back to the Eocene, cranial remains of Palaeogene elephant-shrews, including the middle and inner ear structure, remain unknown. Two macroscelid isolated petrosal bones are described from the late Early–early Middle Eocene Djebel Chambi locality in Tunisia.Chambius kasserinensisis the only macroscelid represented in this locality. A cladistic analysis based on petrosal and inner ear characters highlights the crucial interest of the petrosal and inner ear morphology for understanding the evolution of Macroscelididae. It confirms the attribution of these isolated petrosals toC. kasserinensis. This hypothesis is supported by a common pattern of circulatory system, the morphology of the rostral and caudal tympanic processes, and the shape of the cochlea. In addition,Chambiusappears to be the basal-most taxon among the macroscelid sample; this position is supported by the lack of some specializations of the middle ear such as inflated ossicular bones and pneumatized bulla. The presence of a secondary common crus inChambiussuggests a convergent loss of this structure, at least in Macroscelidea and Tenrecoidea. The petrosal and inner ear characters support the clade Afroinsectivora, which gathers macroscelids with other endemic African insectivorans (tenrecs and golden moles), reinforcing the hypothesis of an African origin of macroscelids. The petrosal bone and inner ear characters provide further morphological support for the debated clade (Petrodromus,Elephantulus rozeti,Macroscelides). New data underlines the fact that the cranial arterial pattern of the Eocene macroscelidChambiuswas already similar to that of modern macroscelid species. It also suggests that early elephant-shrews were probably not as capable of hearing low frequencies as their extant representatives. [ABSTRACT FROM PUBLISHER]

A partial cranium of a very large anthracothere was unearthed during a palaeontological excavation at Saint-Antoine-de-Ficalba (Lot-et-Garonne, France; Early Miocene, ~18–17.0 Ma). The new material, referred to as Brachyodus onoideus (Gervais, 1859 ), documents the cranial features of this species, so far mainly known by dental and postcranial remains. The preserved part of the skull roughly coincides with the neurocranium and is remarkable for the dorsally-protruding orbits, the importance of the postorbital constriction, the small volume of the braincase, and the gigantic size of the occipital condyle relative to the other elements of the neurocranium. A very careful dissection of the left auditory region allowed extraction of the left petrosal bone and provides the first description of a petrosal for Brachyodus. The morphology of the petrosal is strikingly similar to that of extant hippos with: (1) a ventral basicapsular groove, (2) a sharp crista petrosa, (3) a wide prefacial commissure fossa, (4) a reduced mastoid, and (5) an hyperinflated tegmen tympani. Both the disposition of the orifices of the head and the petrosal morphology support a specialization of Brachyodus onoideus to an amphibious lifestyle and to potential underwater directional hearing. [ABSTRACT FROM AUTHOR]

Background: Preservation of fossil vertebrates in volcanic rocks is extremely rare. An articulated skull (cranium and mandible) of a rhinoceros was found in a 9.2±0.1 Ma-old ignimbrite of Cappadocia, Central Turkey. The unusual aspect of the preserved hard tissues of the skull (rough bone surface and brittle dentine) allows suspecting a peri-mortem exposure to a heating source. Methodology/Principal Findings: Here we describe and identify the skull as belonging to the large two-horned rhinocerotine Ceratotherium neumayri, well-known in the late Miocene of the Eastern Mediterranean Province. Gross structural features and microscopic changes of hard tissues (bones and teeth) are then monitored and compared to the results of forensic and archaeological studies and experiments focusing on heating effects, in order to reconstruct the hypothetical peri-mortem conditions. Macroscopic and microscopic structural changes on compact bones (canaliculi and lamellae vanished), as well as partial dentine/cementum disintegration, drastic enamel-dentine disjunctions or microscopic cracks affecting all hard dental tissues (enamel, cementum, and dentine) point to continued exposures to temperatures around 400-450°C. Comparison to other cases of preservation of fossil vertebrates within volcanic rocks points unambiguously to some similarity with the 79 AD Plinian eruption of the Vesuvius, in Italy. Conclusions/Significance: A 9.2±0.1 Ma-old pyroclastic density current, sourced from the Çardak caldera, likely provoked the instant death of the Karacaşar rhino, before the body of the latter experienced severe dehydration (leading to the wide and sustainable opening of the mouth), was then dismembered within the pyroclastic flow of subaerial origin, the skull being separated from the remnant body and baked under a temperature approximating 400°C, then transported northward, rolled, and trapped in disarray into that pyroclastic flow forming the pinkish Kavak-4 ignimbrite ~30 km North from the upper Miocene vent. [ABSTRACT FROM AUTHOR]

We here describe the endocranial cast of the Eocene archaic ungulate Hyopsodus lepidus AMNH 143783 (Bridgerian, North America) reconstructed from X-ray computed microtomography data. This represents the first complete cranial endocast known for Hyopsodontinae. The Hyopsodus endocast is compared to other known "condylarthran" endocasts, i. e. those of Pleuraspidotherium (Pleuraspidotheriidae), Arctocyon (Arctocyonidae), Meniscotherium (Meniscotheriidae), Phenacodus (Phenacodontidae), as well as to basal perissodactyls (Hyracotherium) and artiodactyls (Cebochoerus, Homacodon). Hyopsodus presents one of the highest encephalization quotients of archaic ungulates and shows an "advanced version" of the basal ungulate brain pattern, with a mosaic of archaic characters such as large olfactory bulbs, weak ventral expansion of the neopallium, and absence of neopallium fissuration, as well as more specialized ones such as the relative reduction of the cerebellum compared to cerebrum or the enlargement of the inferior colliculus. As in other archaic ungulates, Hyopsodus midbrain exposure is important, but it exhibits a dorsally protruding largely developed inferior colliculus, a feature unique among "Condylarthra". A potential correlation between the development of the inferior colliculus in Hyopsodus and the use of terrestrial echolocation as observed in extant tenrecs and shrews is discussed. The detailed analysis of the overall morphology of the postcranial skeleton of Hyopsodus indicates a nimble, fast moving animal that likely lived in burrows. This would be compatible with terrestrial echolocation used by the animal to investigate subterranean habitat and/or to minimize predation during nocturnal exploration of the environment. [ABSTRACT FROM AUTHOR]