A complete humerus referred to Agriotherium is described, collected from early-late Hemphillian deposits from Zacatecas. Agriotherium is widely represented by isolated molars, mandibles, and maxillae in early-late Hemphillian faunas of Eurasia and North America. In the literature, postcranial elements are scarce and briefly described with little detail. The greatest diversity is known from the Langebaanweg quarry in South Africa; however, the only complete specimen is from Mexico. The proximal end is described, and the humerus shares similarities with the description of the distal end from South Africa, in which the medial epicondyle and crest of the lateral epicondyle are reduced, which can be considered as a limitation in the hunting of larger prey for food. This implies that Agriotherium was not strictly carnivorous but was a predator-scavenger with an omnivorous diet that included plants and fruits.

Mustelidae are the largest and most diverse family of carnivores, its record dates back to the Early Oligocene, and its early history occurred in western Europe; therefore, the finding of a basal mustelid in southeastern Mexico (northwestern Oaxaca) is quite important. The material found is a very small, nearly complete skull collected from the Yolomécatl Formation, a ~650 m thick lacustrine/fluvial succession interbedded by tuff sheets, yielding a40Ar-39Ar age of 40.3 ± 1.0 Ma, which places this unit and associated fauna in the latest Uintan-earliest Duchesnean NALMAs. However, a purported early Arikareean age has been proposed on the basis of uncritical/unsupported biochronological and isotopic data. The skull is referred to a new genus and species of Mustelidae on the basis of its unique combinaton of plesiomorphic and derived characters. Cladistically, it falls in an unresolved polytomy that inludes only basal European mustelids. This poses a biogeographic problem unsolvable with the evidence at hand: either the new taxon originated in Europe from as yet unknown ancestors, then migrated to southern (tropical) North America, or it evolved there, independently attained the synapomorphies of basal Mustelidae, and migrated to Europe. Finally, the new taxon fits the weasel-ecomorph, approaching the appearance of the extant Mustela frenata, thus suggesting tunnel-hunting habits.

Since the early 2000s, a revival of a felid relationship for barbourofeline sabretooths has become popular due to recent discoveries of fragmentary fossils from Africa. According to this view, barbourofelines trace their common ancestor with felids through shared similarities in dental morphology going back to the early Miocene of Africa and Europe. However, whether or not such an idea is represented in the basicranial morphology, a conservative area of high importance in family-level relationships, is yet to be tested. A nearly complete skull of Oriensmilus liupanensis gen. and sp. nov. from the middle Miocene Tongxin Basin of northern China represents the most primitive known barbourofeline with an intact basicranial region, affording an opportunity to re-examine the relationship of felids and nimravines. We also present an update on East Asian records of barbourofelines. The new skull of Oriensmilus possesses a suite of characters shared with nimravines, such as the lack of an ossified (entotympanic) bullar floor, absence of an intrabullar septum, lack of a ventral promontorial process of the petrosal, presence of a small rostral entotympanic on the dorsal side of the caudal entotympanic, and a distinct caudal entry of the internal carotid artery and nerve that pierces the caudal entotympanic at the junction of the ossified and unossified caudal entotympanics. The absence of an ossified bullar floor in O. liupanensis and its presence in those from the middle Miocene of Sansan, France thus help to bracket the transition of this character, which must have happened in the early part of the middle Miocene. Spatial relationships between bullar construction and the middle ear configuration of the carotid artery in Oriensmilus strongly resemble those in nimravines but are distinctly different from felids and other basal feliforms. Despite the attractive notion that early barbourofelines arose from a Miocene ancestor that also gave rise to felids, the basicranial evidence argues against this view. http://zoobank.org/urn:http://lsid:zoobank.org:pub:2DE98DBC-4D02-4E18-9788-0B0D8587E73F.

Thick successions of middle and late Cenozoic sedimentary rocks occur in the Linxia Basin of China. These deposits comprise an archive recording spatiotemporal patterns of mountain uplift, erosion, basin deformation, and associated changes in the monsoon, as a result of the growth of the northeastern Tibetan Plateau. The Linxia Basin is also world famous for its abundant and diverse vertebrate fossils that shed light on Cenozoic terrestrial ecosystem evolution; however, previous studies of these important fossils have been beset by issues related to commercial excavation and associated difficulties in ascertaining provenance, with many specimens in private collections. Despite years of intensive studies by geologists from Lanzhou University and vertebrate paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), aspects of basin stratigraphy and chronology still remain controversial. The heart of these controversies often revolves around questions of imprecise fossil provenance and related casual references of fossils as age tie-points, different interpretations of lithostratigraphic units at different localities across the basin, and ultimately different age determinations. In this special issue, entitled Biostratigraphy, Chronostratigraphy and Vertebrate Paleontology of the Linxia Basin, we report the findings of an IVPP project, funded by the Chinese Academy of Sciences, which addresses these controversies, proposes a new age model for basin, and develops understanding of the fossil assemblages. In this introduction to the special issue, we review the tectonic context for basin evolution and chronology as well as lithostratigraphy, paleoenvironments and climates. While issues of provenance remain challenging and will continue to burden Chinese vertebrate paleontologists into the future, our findings shed new light on the vertebrate paleontology of the Linxia Basin, and unique circumstances in which it developed.

Early Cenozoic "insectivorans" possess some of the most primitive morphologies among eutherian mammals. Studies of these archaic mammals offer insights into the early diversifications of basal eutherians. Despite such importance, early fossil "insectivorans" from Asia are poorly known due to a scarcity of fossil remains, which often consist only of fragmentary jaws and teeth. Discoveries of remarkably well-preserved fossil "insectivorans", including complete skulls and articulated postcranial skeletons, from the early Eocene Hengyang Basin in south-central Hunan Province, China, offer a rare opportunity to thoroughly study two taxa belonging to different families. Fine-grained red beds from Hengyang Basin preserve extraordinary fossils with morphological structures rarely seen elsewhere. Thin sections of a skull of Hsiangolestes youngiZheng and Huang, 1984, for example, reveal the extremely delicate nasal and maxillary turbinates, which, as far as we are aware, are the first known from fossils of this age. We thus take this opportunity to document in detail the cranial and dental morphology, as well as postcranial skeletons, of the Hengyang "insectivorans.". In this monograph, we describe several complete skulls and serial sections of a skull, as well as many partial skulls, mandibles, and postcranial skeletons of Hsiangolestes youngi, an Asian early Eocene insectivoran-grade mammal. We also report a new species of NaraniusRussell and Dashzeveg, 1986 - N. hengdongensis - an Asian early Eocene cimolestid and describe its well-preserved skulls and mandibles. Hsiangolestes is endemic to Asia. It is currently known only from the earliest Eocene Lingcha Formation, Hengyang Basin, Hunan Province, China. Naranius closely resembles CimolestesMarsh, 1889, the type genus of the family Cimolestidae. It is mainly distributed in Asia and known from the earliest Eocene deposits in the Bumban Member of the Naran Bulak Formation, Nemegt Basin, of Mongolia, and the Lingcha Formation, Hengyang Basin, Hunan Province, China. The only record of Naranius reported outside of Asia is N. americanus from the early Wasatchian Red Hot Local Fauna, Mississippi, United States. Using PAUP and TNT search algorithms, we place these Hengyang taxa within phylogenetic context of other fossil "insectivorans" from the Mesozoic and early Cenozoic of Asia together with some well-known Holarctic taxa. A phylogenetic analysis of 290 cranial and dental characters from 36 fossil and modern insectivoran-grade taxa is presented, focusing on new materials of Hsiangolestes youngi and Naranius hengdongensis. Based on the results of our phylogenetic analyses, we propose that (1) Hsiangolestes, Prosarcodon, Sarcodon, and Sinosinopa, form a monophyletic group, for which we propose the family name Sarcodontidae; (2) the family Cimolestidae should be restricted to Naranius and Cimolestes, which are sister taxa; (3) the systematic position of Naranius americanus is uncertain; and (4) the family Micropternodontidae should be restricted to Micropternodus and its allies in North America.

Explorations in the past 20 years in the Plio-Pleistocene Zanda Basin (3,800–4,500 m above sea level) along the northern slopes of the Himalaya Mountains have substantially enriched our understanding of the paleoenvironments of the Tibetan Plateau and associated biologic evolution. Many elements of the mammalian fauna recovered are either new to science or shed new light about their special adaptations in this high elevation basin. Here we describe a new species of twisted-horned antelope, Gazellospira tsaparangensis, with a heteronymous spiral. Its small size and primitive morphology, such as relatively short horncore with less twisting, thin frontal bones, a lack of frontal and horncore sinuses, small size of supraorbital foramina, and lack of an anterior keel, helps to place it at the base of genus Gazellospira, substantially more stem-ward than the type species G. torticornis from the Plio-Pleistocene of Europe and western Asia. With an estimated age of 3.62 Ma, this also places G. tsaparangensis as one of the early occurrences in Eurasia, although some fragmentary records in Turkey may be slightly earlier. Considering this early appearance and primitive morphology, G. tsaparangensis once again may be a case of the ‘out-of-Tibet’ model of megafauna origin, with earlier progenitors adapted to cold environments in high Tibet before expanding their range to the rest of Eurasia.

Well adapted to extremely cold winters (hypothermia) and low oxygen (hypoxia), the Tibetan antelope (or chiru), Pantholops hodgsonii Abel, is an iconic species in the Tibetan Plateau. Its extinct relative, Qurliqnoria Bohlin, represents the earliest endemic Tibetan mammal going back to the late Miocene, suggesting a long process of adaptations within Tibetan Plateau for ~ 10 million years. We reexamine holotype materials of Q. hundesiensis (Lydekker) from the British Museum, originally discovered by British explorers in the Himalayas in the early 1800s, and new materials recently discovered in the Pliocene strata of Zanda Basin, southwestern Tibet. We refer additional horncore and dental materials from the Kunlun Pass Basin at 4,700–4,900 m asl, and leverage these new data to place Q. hundesiensis within modern biostratigraphic and paleoenvironmental frameworks. Although Qurliqnoria remains the best candidate of a distant sister-group of living Pantholops, the Pliocene representatives offer no sign of transitions to living chiru. We infer that the Qurliqnoria lineage has persisted throughout late Miocene and Pliocene of the Tibetan Plateau in a chronospecies succession, i.e., Q. cheni to Q. hundesiensis. The Pliocene Qurliqnoria probably did not directly give rise to Pantholops, suggesting that a direct ancestor of Pantholops is yet to be found. We discuss the paleoenvironmental and paleoelevational implications of the new Qurliqnoria materials and analysis for Tibetan Plateau faunal evolution.

Modern wild sheep, Ovis, is widespread in the mountain ranges of the Caucasus through Himalaya, Tibetan Plateau, Tianshan-Altai, eastern Siberia, and the Rocky Mountains in North America. In Eurasia, fossil sheep are known at a few Pleistocene sites in North China, eastern Siberia, and western Europe, but are so far absent from the Tibetan Plateau. We describe an extinct sheep, Protovis himalayensis, gen. et sp. nov., from the Pliocene of the Zanda Basin in western Himalaya. Smaller than the living argali, this new form shares with Ovis posterolaterally arched horncores and partially developed sinuses and possesses several transitional characters leading to Ovis. Protovis likely subsisted on C3 plants, which are the dominant vegetation in the Zanda area during the Pliocene. With the discovery of this new genus and species, we extend the fossil record for the sheep clade into the Pliocene of the Tibetan Plateau, consistent with our previous out-of-Tibet hypothesis. Ancestral sheep in the Pliocene were presumed adapted to high altitude and cold environments, and during the Ice Age, sheep became anatomically modern and dispersed outside of the Tibetan Plateau. Both this new fossil datum and the existing molecular phylogeny suggest that the Tibetan Plateau, possibly including Tianshan-Altai, represents the ancestral home range(s) of mountain sheep and that these basal stocks were the ultimate source of all extant species. Most sheep species survived along their Pleistocene route of dispersal, offering a highly consistent pattern of zoogeography. http://zoobank.org/urn:lsid:zoobank.org:pub:F2AEE746-0A5B-4F40-89B7-8EF0C04F21FD SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Wang, X., Q. Li, and G. T. Takeuchi. 2016. Out of Tibet: an early sheep from the Pliocene of Tibet, Protovis himalayensis, gen. et sp. nov. (Bovidae, Caprini), and origin of Ice Age mountain sheep. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1169190.