Linxia Basin Research Articles

A new rhinocerotoids (Mammalia, Perissodactyla) from the Late Oligocene of Linxia Basin, China

ABSTRACT The Jiaozigou Formation, the lowest fossiliferous stratum in the Linxia Basin, produces the most abundant mammalian fossils in East Asia. Although the Jiaozigou Fauna is renowned for the ‘giant rhino’ (Paraceratheriidae), evidence of relatively small rhinocerotoids is scant, consisting only of fragments. The newly identified species, Megacanodon dongxiangense gen. et sp. nov. is characterised by its small-sized body, the presence of a large canine, nearly completely molarised upper premolars, retracted nasal notch, and not-elevated occipital part. It remains unclear whether the new genus is phylogenetically close to Hyracodontidae, Eggysodontidae, or Rhinocerotidae. We tentatively designate it as a basal genus within Rhinocerotoidea, with the uncertain family affiliation.

When the woolly rhinoceroses roamed East Asia: a review of isotopic paleoecology of the genus Coelodonta from the Tibetan Plateau to northern Eurasia

East Asia, being the evolutionary center of Coelodonta, offers a unique opportunity to explore the spatiotemporal paleoecologies of this genus. This study utilized bulk and serial stable carbon and oxygen isotope analyses on the Coelodonta nihowanensis and other ungulates from the Longdan fauna as well as two modern goats in the Linxia Basin, aiming to explore the paleoecology of C. nihowanensis at the periphery of the Tibetan Plateau during the Early Pleistocene. The isotopic results of these mammals indicated that C3 vegetation was possibly a major component of the local environment in the Linxia Basin, which was influenced by a seasonal summer monsoon. C. nihowanensis specimens in the Longdan fauna were possibly mixed feeders, as indicated by the wide distribution of their δ13C values and the intermediate δ18O values compared to other coexisting ungulates. Moreover, the comparison of the δ13C and δ18O values of similar taxa from the Linxia and Nihewan basins has revealed spatiotemporal differences in the paleoclimate and paleoenvironments of these two regions throughout the Early Pleistocene. This provides a holistic framework for understanding the paleoecology of the C. nihowanensis. The isotopic results of the C. nihowanensis in the Linxia and Nihewan basins suggested varied foraging ecologies across different sites and time spans during the Early Pleistocene. This underscores the adaptability of the C. nihowanensis to diverse environments from west to east in northern China. By scrutinizing the evolutionary ecological history of the woolly rhinoceroses from its ancestor, Coelodonta thibetana, to its final form, Coelodonta antiquitatis, this study sheds light on the ecological adaptation of this genus from the Pliocene to Late Pleistocene, spanning its migration from the Tibetan Plateau to northern Eurasia.

Fossil Equidae in the Linxia Basin with Biostratigraphic and Paleozoogeographic Significance

AbstractThe Linxia Basin is characterized by an abundance of Cenozoic sediments, that contain exceptionally rich fossil resources. Equids are abundant in the Linxia Basin, the fossil record of equids in this region including 16 species that represent 10 genera. In comparison to other classic late Cenozoic areas in China, the Linxia Basin stands out, because the fauna and chronological data accompanying Linxia equids render them remarkably useful for biostratigraphy. The anchitheriines in the region, such as Anchitherium and Sinohippus, represent early equids that appeared in the late stages of the middle and late Miocene, respectively. Among the equines, most species of Chinese hipparions have been identified in the Linxia Basin and some species of the genera Hipparion and Hippotherium have FAD records for China. Furthermore, Equus eisenmannae is one of the earliest known species of Equus in the Old World and is well‐represented at the Longdan locality. Some species with precise geohistorical distributions can serve as standards for high‐resolution chronological units within this framework. Located at the eastern margin of the Tibetan Plateau and subject to considerable uplift, the Linxia Basin has served as a biogeographic transition area for equids throughout the late Cenozoic.

New materials of Pliorhinus ringstroemi from the Linxia Basin (Late Miocene, eastern Asia) and their taxonomical and evolutionary implications

New materials of Pliorhinus ringstroemi from the Linxia Basin (Late Miocene, eastern Asia) and their taxonomical and evolutionary implications

Neogene drainage reorganization of Longzhong Basin driven by growth of the northeastern Tibetan Plateau: A Sr isotope hydrological perspective

AbstractThe Tibetan Plateau uplift has significantly influenced Asian geomorphic and climate patterns. Drainage evolution across the plateau and its surroundings as the consequence of such changes in landscape and climate provides an opportunity to understand the growth of the Tibetan Plateau. However, the evolution history of major drainage areas around the Tibetan Plateau is largely unknown. Here, we reconstructed the evolution of drainage patterns of the Cenozoic Longzhong Basin in the northeastern Tibetan Plateau since the India–Asia collision using palaeo‐water solute 87Sr/86Sr ratio records from its subbasins. Higher solute 87Sr/86Sr ratios of the Lanzhou and Xining Basins and their consistent temporal variations before ca. 22 Ma as well as lower solute 87Sr/86Sr ratios in the Linxia Basin collectively indicate a relatively steady drainage pattern of the integrated Longzhong Basin. A diverse evolution of the solute 87Sr/86Sr ratio in the Lanzhou and Xining Basins after ca. 22 Ma suggests that there was a drainage reorganization, characterized by the division of one into multiple catchment centres, in response to the growth of the northeastern Tibetan Plateau. Subsequently, the identical solute 87Sr/86Sr ratios in the Lanzhou and Xining Basins were further approached at ca. 16 Ma, and the rise in the solute 87Sr/86Sr ratios of the Linxia and Tianshui Basins occurred at ca. 9–8 Ma, indicating two subsequent changes in solute composition induced by the middle Miocene uplift and late Miocene dust expansion, respectively. Our reconstructions of Cenozoic hydrological evolution in the Longzhong Basin indicate accelerated basin segmentation and drainage adjustment with solute change in response to the growth of the northeastern Tibetan Plateau during the Neogene.

Stratigraphic context of Oligocene to Pliocene mammal-bearing deposits in Linxia Basin, Gansu Province, China: a historical review and a discussion of ongoing controversies

In this paper, we critically review the half-century (1962–2022) history of study of Oligocene to Pliocene mammal-bearing successions in the eastern Linxia Basin, Gansu Province, China. Despite great strides in our understanding of the regional geology and the discovery of a large quantity of mammal fossils, there remains major discrepancies concerning the definition and age assignment of the formations that comprise the Linxia Group. This has resulted in the development of two competing schemes for its subdivision: the first scheme was proposed by geologists of the Lanzhou University and the Institute of Tibetan Plateau Research, and the second scheme is associated with paleontologists of the Institute of Vertebrate Paleontology and Paleoanthropology. In an attempt to solve these discrepancies, a five year project was initiated in 2017, and herein we report the main findings as follows: (1) The Jiaozigou Formation does not extend into the Miocene, with its top calibrated at about 23 Ma; (2) The Liushu Formation, as defined in the Maogou section, should be considered as the penecontemporaneous shallow water facies of the coarse-grained Hujialiang Formation of Middle Miocene age; (3) The widespread Hipparion-bearing deposits along the Guangtong River, which have been also referred to the “Liushu” Formation represent a different stratigraphic unit and should be given another name to eliminate confusion following further stratigraphic analysis.

Global warming drove the Mid-Miocene climate humidification in the northern Tibetan Plateau

The Miocene is a key transitional period for the Asian monsoon evolution and establishment of modern-like geomorphic landscapes in the northern Tibetan Plateau. Elucidating the Miocene paleoenvironmental changes and their relationships with climate and tectonics are significant in understanding future hydrological changes in the northern Tibet under a warming climate. In this study, detailed lithological and rock magnetic investigations were conducted on a Miocene fluvial-lacustrine sediment sequence from the Linxia Basin in Northeast Tibet, to understand the paleoenvironmental and palaeohydrological response to the tectonics and global climatic change, especially to the effects of the Middle Miocene Climatic optimum (MMCO). The results demonstrated that strong waterlogged reducing environments during MMCO precluded the occurrences of pedogenesis in the Linxia Basin owing to highly humid climates. As the precipitation decreased significantly before and after MMCO, pedogenesis occurred increasingly owing to temperate and well-drained conditions. A synthesis of the lithological and magnetic variations in Miocene fluvial-lacustrine sediments further indicated that climate humidification prevailed in most areas of the northern Tibetan Plateau during MMCO. These observations demonstrate that global climate change, rather than the tectonic uplift, significantly influenced the Mid-Miocene paleoenvironmental evolution in northern Tibet.

Cosmogenic nuclide chronological constraints on the late Cenozoic strata of the Linxia Basin, northeast Tibetan Plateau

The thick Cenozoic sedimentary sequence of the Linxia Basin contains abundant well-preserved mammalian fossils, which provide significant information on the paleoenvironmental processes and mammalian evolution associated with the uplift and expansion of the Tibetan Plateau. Ambiguous age estimations have been made for some coarse-grained sedimentary units in the basin, which have led to the misinterpretation of biostratigraphic and magnetostratigraphic age models. To resolve these issues, we present radiometric dating of three late Cenozoic sedimentary units (“Liushu”, Hewangjia, and Jishi formations) in the eastern Linxia Basin using cosmogenic 26Al/10Be and 10Be/21Ne burial methods. isotope measurements for the upper “Liushu” Formation indicate a 10Be/21Ne burial age of 11.70 ± 0.17 Ma. This age is older than, but not contrary to, recently revised bio-magnetostratigraphic work. The 26Al/10Be burial age of the Hewangjia Formation is 3.06 (+0.36/−0.31) Ma and had been underestimated by post-burial muon production possibility, while the 26Al/10Be burial age of the Jishi Formation is 2.50 (+0.20/−0.18) Ma and had been overestimated due to inherited cosmogenic nuclides from recycled deposits. The new age from the Jishi Formation delays the initial deposition of conglomerates in the Linxia Basin to no earlier than 2.5 Ma and constrains an important episode of tectonic uplift of the northeastern Tibetan Plateau to 2.5–3.1 Ma. The age of the Equus fauna of Longdan is revised to the Early Quaternary (ca. 2.1–1.9 Ma). Our new age determinations significantly refine the terrestrial sequence chronology of the Linxia Basin and associated mammalian faunas of the late Miocene to the early Pleistocene.

Study on the new dental material of Palaeotragus from the Late Miocene of Linxia Basin (Gansu, China)

ABSTRACT Palaeotragus is a common genus of the Giraffidae that was widely distributed in the Neogene strata of Eurasia. Early studies usually placed small giraffids in the Palaeotragus clade, leading to considerable controversy over the validity and systematic classification of this genus. Palaeotragus microdon and Palaeotragus cf. coelophrys are two representative species of Palaeotragus in China, their dental specimens are mainly distinguished by size, causing problems in their actual identification. In this study, several mandibles of a small giraffid found in Linxia Basin, Gansu Province, China (MN 10–13), are studied and identified as Palaeotragus cf. coelophrys. Based on a detailed comparison, the size and morphological variability of the Chinese Palaeotragus dental material are discussed, as well as the validity of the two species and the validity of other Eurasian Palaeotragus. This study reveals that the Chinese Palaeotragus has a continuous sequence of size variability and premolar features, which is insufficient to separate the mandible of the two species. In addition, the type species P. rouenii can be clearly distinguished from the Chinese Palaeotragus by the relatively long lower premolar row, possibly due to the difference in feeding habits. The holotype of P. coelophrys is closely related to Chinese Palaeotragus, while the P. coelophrys mandible from Maragheh (MMTT37 2517) should belong to different species.

Cenozoic tectonosedimentary evolution of the Linxia Basin, northeast Tibetan Plateau based on an analysis of detrital zircon provenance

The Linxia Basin is an important region for understanding the tectonism and uplift history in the northeast Tibetan Plateau, and also contains rich mammalian faunas of evolutionary significance. In this paper, we conduct a provenance study of Cenozoic sediments, relying primarily on U-Pb dating of detrital zircons, to investigate the exhumation history of surrounding terranes and to gain a better understanding of the relationship between tectonism, basin development and paleoenvironment.Samples were collected from the Maogou section in the central Linxia Basin, which has been recently dated by magnetostratigraphy. Detrital zircon populations show five UPb age groups of 65–350 Ma, 350–600 Ma, 600–1600 Ma, 1600–2200 Ma and 2200–2600 Ma; however, UPb age patterns varied up-section, indicating different sources at different times.Sediments from the lower part of the section (>27.8 Ma) were sourced from multiple regions, including the distal East Kunlun Shan, Qilian Shan, and Songpan–Ganzi terranes, and as well as the proximal West Qinling region. Contributions from the Songpan–Ganzi terrane increased considerably during the late Oligocene (27.8–23 Ma), as a result of strong tectonic movements of the northeastern Tibetan Plateau. During the early Miocene (23–17.2 Ma), the northern sources of the Laji Shan–Maxian Shan region supplied more sediments to the basin, indicating the uplift and exhumation of these mountain ranges. Until the middle Miocene (17.2–12.8 Ma), the Songpan-Ganzi terrane and the northern sources dominated the basin sediments, while the northern sources and the Jishi Shan region became increasingly important sources at around 11.6 Ma. This study explores the tectonosedimentary evolution of the Linxia Basin in the northeastern Tibetan Plateau, providing a reference for further research of the paleoclimate and mammalian evolution in this critical region.

A biostratigraphic and palaeoecological study of Late Cenozoic kubanochoeres from the Linxia Basin, Gansu Province, China

The Linxia Basin of Gansu Province, China contains the most complete record of Miocene kubanochoere fossils from Eurasia. A kubanochoere discovered in the late Early Miocene Shangzhuang Formation (ca. 17.2 Ma) is the earliest known member of the group from Eurasia; it is slightly older than the medium-sized Kubanochoerus marymunnguae discovered in Africa, and may indicate an Eurasian origin for kubanochoeres. A giant-sized kubanochoere found in the upper part of the Middle Miocene Dongxiang Formation (ca. 14.6–12.8 Ma) also occurs in the Dingjiaergou fauna (Ningxia Hui Autonomous Region) and the Halamagai fauna (Xinjiang Uygur Autonomous Region), of a similar age. Large-sized kubanochoeres discovered in the upper part of the Dongxiang Formation (ca. 14.6–12.8 Ma) and in the late Middle Miocene Hujialiang Formation (ca. 12.8–12.4 Ma) are widespread and elsewhere found in the Dingjiaergou fauna, the Halamagai fauna, the Kekemaideng fauna (Xinjiang Uygur Autonomous Region), the Koujiacun fauna (Shaanxi Province), and the Quantougou fauna (Gansu Province); they partly coexist with giant or medium-sized kubanochoeres in some localities. Medium-sized kubanochoeres recovered from the boundary between the Hujialiang Formation and the “Liushu Formation” (ca. 12.4–11.6 Ma) are also found in the Laogou fauna, the Lierbao fauna (Qinghai Province) and the Kangping fauna (Gansu Province). Due to significant changes in temperature and atmospheric CO2 during the Mid-Miocene Climatic Optimum and the Mid-Miocene Climate Transition, decreasing levels of available nutrition likely influenced the evolution and size of the kubanochoeres. Coexisting fossil suids may have been another important factor in the extinction of the kubanochoeres in Eurasia and Africa.

Revised magnetostratigraphy of the Linxia Basin in the northeast Tibetan Plateau, constrained by micromammalian fossils

The Linxia Basin along the northeastern margin of the Tibetan Plateau has drawn enormous attention due to its rich mammalian fossils and great potential for exploring regional tectonics, paleoenvironmental history, and bio-evolution. However, the geochronology of the sedimentary sequences is in great dispute owing to uncertain lithostratigraphic correlation and poorly calibrated magnetostratigraphy. From 2017 to 2021, we carried out lithostratigraphic correlation of the strata from the southern part of the basin, which is rich in fossils, to the Maogou section in the central basin, and established a solid intra-basinal lithostratigraphic framework with accurate fossil locations. Then, high-resolution magnetostratigraphic investigations were performed on the Maogou section, which comprises, from oldest to youngest, the Jiaozigou, Shangzhuang, Dongxiang, Liushu/Hujialiang, and “Liushu” formations. Magnetostratigraphic results show that the Maogou sedimentary sequence (from Jiaozigou to Liushu/Hujialiang formations) spans from chron C10r to chron C5r.2n, yielding an age of 29–11.6 Ma, with constraints from four mammalian assemblage levels. The revised magnetostratigraphy indicates that the Jiaozigou Formation corresponds to chrons C6Cn.3n–C10r (∼23–29 Ma), with Paraceratherium fauna from the lower Jiaozigou Formation being determined as ∼29 Ma, and that the Hujialiang Formation, containing Platybelodon fauna, corresponds to chrons C5r.2n–C5Ar.2r (∼11.6–12.8 Ma). The revised magnetostratigraphy of the Maogou section has significantly refined the chronology of the Linxia Basin sedimentary sequences and its associated mammalian evolution, tectonism, and climate change in Central Asia.

Evolutionary and biogeographic implications of an Erycine snake (Serpentes, Erycidae, Eryx) from the Upper Miocene of the Linxia Basin, Gansu Province, China

Evolutionary and biogeographic implications of an Erycine snake (Serpentes, Erycidae, Eryx) from the Upper Miocene of the Linxia Basin, Gansu Province, China

3D models related to the publication: Miocene Moschidae (Mammalia, Ruminantia) from the Linxia Basin (China) connect Europe and Asia and show early evolutionary diversity of a today monogeneric family

3D models related to the publication: Miocene Moschidae (Mammalia, Ruminantia) from the Linxia Basin (China) connect Europe and Asia and show early evolutionary diversity of a today monogeneric family

Origin of adaptations to open environments and social behaviour in sabretoothed cats from the northeastern border of the Tibetan Plateau.

The iconic sabretooth Homotherium is thought to have hunted cooperatively, but the origin of this behaviour and correlated morphological adaptations are largely unexplored. Here we report the most primitive species of Amphimachairodus (Amphimachairodus hezhengensis sp. nov.), a member of Machairodontini basal to Homotherium, from the Linxia Basin, northeastern border of the Tibetan Plateau (9.8-8.7 Ma). The long snout, laterally oriented and posteriorly located orbit of Amphimachairodus suggest a better ability to observe the surrounding environment, rather than targeting single prey, pointing to an adaptation to the open environment or social behaviour. A pathological forepaw of Amphimachairodus provides direct evidence of partner care. Our analyses of trait evolutionary rates support that traits correlated with killing behaviour and open environment adaptation evolved prior to other traits, suggesting that changes in hunting behaviour may be the major evolutionary driver in the early evolution of the lineage. A. hezhengensis represents one of the most important transitions in the evolution of Machairodontini, leading to adaptation in open environments and contributing to their further dispersal and radiation worldwide. This rapid morphological change is likely to be correlated with increasingly arid environments caused by the rise of the Tibetan Plateau, and competition from abundant large carnivores in this area.

Fossil bovids from the Linxia Basin of Gansu Province, China, and their implications for regional biostratigraphy, palaeogeography and palaeoecology

Fossil bovids are key components of the Neogene mammal faunas in Eurasia, showing high diversity and rapid rates of evolution, with important implications for biostratigraphy and understanding past climate change. The Linxia Basin (Gansu Province, China) contains rich Miocene to Early Pleistocene bovid assemblages that provide an opportunity to study the evolution of this group. This paper reviews the fossil record of bovids in the Linxia Basin, which comprises more than 20 genera within seven tribes, spanning nine stratigraphic horizons and distributed across 43 fossil localities. Findings show that the diversity of fossil bovids in the Linxia Basin increased dramatically from the Early to Late Miocene but fell suddenly at the end of the Late Miocene before reaching a second peak in the Early Pleistocene. The Late Miocene mammal assemblages from the Linxia Basin may indicate somewhat younger age than previously thought based on fossil bovid comparisons. With diverse species and rich material, the bovids of the Linxia Basin present an excellent opportunity for further studies on morphology and adaptations within the group.

Miocene Moschidae (Mammalia, Ruminantia) from the Linxia Basin (China) connect Europe and Asia and show an early evolutionary diversity of a today monogeneric family

Moschidae are the only pecoran ruminants where all representatives totally lack cranial appendages today. Latest phylogenetic studies name them the sister group of Bovidae. Thus, cladogenesis of Moschidae and Bovidae should be older than the earliest known bovids (∼18 Ma). However, the oldest known moschid fossil so far dates to about 16 Ma years old in Eastern Europe. This and other early records so far comprise few fossils and thus, the early evolution as well as the origin of the extant Moschus is not yet fully known. Here, we report new results on the Moschidae from the Shinanu Fauna, Linxia Basin, older than 15 Ma. New and historic material reveal some of the oldest records of Moschidae and an unexpected rich diversity, especially for this early phase of evolution. A new taxon, ‘Micromeryx’ caoi sp. nov., presents affinities with the late Middle Miocene species ‘M.’ eiselei from Steinheim am Albuch. The second new taxon represents the oldest described Hispanomeryx species, Hispanomeryx linxiaensis sp. nov. and confirms an Asian Hispanomeryx-lineage. Furthermore, there may be one additional so far undetermined large moschid in the basin during this time slice. Our results provide essential data for a possible Asiatic origin of the Moschidae, and for their early evolution, and improve our understanding of terrestrial Early Miocene ecosystems in East Asia.

Miocene squirrels from Linxia Basin, Gansu, China; paleoenvironmental and palaeoecological implications

This paper presents the Miocene squirrels of the Linxia Basin in Gansu Province, and a paleoenvironmental and palaeoecological analysis based on the remains collected recently by screen-washing nine localities of early to late Miocene age. The assemblages contain 12 sciurid species (nine genera, three subfamilies), including squirrels with different adaptations, predominantly ground squirrels and chipmunks. Our analysis suggests that Miocene squirrels in Linxia reflect a relatively dry climate and open shrub-steppe environment, and favorable dispersal across Eurasia. The Linxia Miocene squirrels show close taxonomic composition with contemporary faunas known from the Mongol-Xinjiang highland and adjacent regions, implying that northern China represents a single biotic province with uniform paleoenvironment. In addition, the Linxia squirrels are quite different from those found in Yunnan in southern China, which are dominantly tree and flying squirrels that suggest a humid forest biotope. The differences in distribution indicate that Miocene squirrel faunas of China showed distinct provinciality and latitudinal ecological variation. Already in the Miocene we see evidence for predecessors of the present-day Palearctic and Oriental zoogeographic provinces of North and South China.

Middle Cenozoic micromammals from Linxia Basin, Gansu Province, China, and their implications for biostratigraphy and palaeoecology

We report late Oligocene to late Pliocene micromammal assemblages from 19 localities of the Linxia Basin of Gansu Province, China. Abundant material (> 7000 specimens) includes members of Eulipotyphla, Chiroptera, Rodentia and Lagomorpha, and comprises 121 species arranged in 24 families. The Yagou assemblage (basal part of the Jiaozigou Formation) is one of the few early Late Oligocene micromammalian faunas known from China. The Galijia (Dongxiang Formation) and Yihachi (“Liushu” Formation) assemblages represent the richest and most productive middle and late Miocene micromammal faunas known from northwestern China. These middle Cenozoic faunas show a closely similar community structure and taxonomic composition, and a similar pattern of faunal turnover, with contemporary faunas throughout the Mongol-Xinjiang Region, implying the existence of a unified biogeographic zone. The discoveries contribute to the temporal ordering of individual fossil assemblages of northern China and help develop a framework for Cenozoic biostratigraphy and biochronology in central Asia. Our palaeoenvironmental analysis suggests change towards warmer and moister equable habitats of the late Oligocene to early and middle Miocene, followed by the onset of drier temperate shrub-steppe environments. The composition of extant families of micromammals that developed during the Neogene reflects a faunal distribution analogous to the Holarctic Region today and suggests a shared ecology.

Chronological framework and palaeoecology of Carnivora from the Linxia Basin, China

The Linxia Basin has produced some of the most complete and fossiliferous fossil assemblages among the known late Cenozoic basins including diverse carnivoran elements. In this work, we summarize the chronological framework for its fossil Carnivora based on current knowledge. A total of 80 species of Carnivora, belonging to 55 genera and 10 families, are currently recorded in 10 assemblages. Three faunas with Carnivora of Middle Miocene age, include amphicyonids, hemicyonids, and percrocutids. Five assemblages dating to the late Miocene and the earliest Pliocene hipparion faunas, are represented by very abundant ictitherine hyaenids, the giant hyaena Dinocrocuta, the large machairodont Amphimachairodus and diverse metailurine felids, and various mustelids. The Late Pliocene records scant material, but the Early Pleistocene Equus fauna is well represented by canids, hyaenids, a lynx, and Megantereon. A major Carnivoran guild turnover occurs at the boundary of the Middle and Late Miocene. The Linxia Basin experienced earlier aridification in the Late Miocene than did Europe, likely correlated with the rise of Tibet. The medial body size of Carnivora remains largely unchanged from the Middle Miocene to the Early Pleistocene. Crown-group members (at the family level) increased dramatically in proportion during the Late Miocene, and remained largely unchanged since the latest Miocene, suggesting that the Late Miocene is the major period of emplacement of current Carnivora phylogenetic structure.