Gary T. Takeuchi

Out of Tibet: Pliocene woolly rhino suggests high-plateau origin of Ice Age megaherbivores.

The Tibetan Plateau acted as a cradle of adaptation to cold for Pleistocene megafauna. Ice Age megafauna have long been known to be associated with global cooling during the Pleistocene, and their adaptations to cold environments, such as large body size, long hair, and snow-sweeping structures, are best exemplified by the woolly mammoths and woolly rhinos. These traits were assumed to have evolved as a response to the ice sheet expansion. We report a new Pliocene mammal assemblage from a high-altitude basin in the western Himalayas, including a primitive woolly rhino. These new Tibetan fossils suggest that some megaherbivores first evolved in Tibet before the beginning of the Ice Age. The cold winters in high Tibet served as a habituation ground for the megaherbivores, which became preadapted for the Ice Age, successfully expanding to the Eurasian mammoth steppe.

Himalayan fossils of the oldest known pantherine establish ancient origin of big cats

Pantherine felids (‘big cats’) include the largest living cats, apex predators in their respective ecosystems. They are also the earliest diverging living cat lineage, and thus are important for understanding the evolution of all subsequent felid groups. Although the oldest pantherine fossils occur in Africa, molecular phylogenies point to Asia as their region of origin. This paradox cannot be reconciled using current knowledge, mainly because early big cat fossils are exceedingly rare and fragmentary. Here, we report the discovery of a fossil pantherine from the Tibetan Himalaya, with an age of Late Miocene–Early Pliocene, replacing African records as the oldest pantherine. A ‘total evidence’ phylogenetic analysis of pantherines indicates that the new cat is closely related to the snow leopard and exhibits intermediate characteristics on the evolutionary line to the largest cats. Historical biogeographic models provide robust support for the Asian origin of pantherines. The combined analyses indicate that 75% of the divergence events in the pantherine lineage extended back to the Miocene, up to 7 Myr earlier than previously estimated. The deeper evolutionary origin of big cats revealed by the new fossils and analyses indicate a close association between Tibetan Plateau uplift and diversification of the earliest living cats.

Locomotive implication of a Pliocene three-toed horse skeleton from Tibet and its paleo-altimetry significance

The Tibetan Plateau is the youngest and highest plateau on Earth, and its elevation reaches one-third of the height of the troposphere, with profound dynamic and thermal effects on atmospheric circulation and climate. The uplift of the Tibetan Plateau was an important factor of global climate change during the late Cenozoic and strongly influenced the development of the Asian monsoon system. However, there have been heated debates about the history and process of Tibetan Plateau uplift, especially the paleo-altimetry in different geological ages. Here we report a well-preserved skeleton of a 4.6 million-y-old three-toed horse (Hipparion zandaense) from the Zanda Basin, southwestern Tibet. Morphological features indicate that H. zandaense was a cursorial horse that lived in alpine steppe habitats. Because this open landscape would be situated above the timberline on the steep southern margin of the Tibetan Plateau, the elevation of the Zanda Basin at 4.6 Ma was estimated to be ∼4,000 m above sea level using an adjustment to the paleo-temperature in the middle Pliocene, as well as comparison with modern vegetation vertical zones. Thus, we conclude that the southwestern Tibetan Plateau achieved the present-day elevation in the mid-Pliocene.

A partial skeleton of the Late Cretaceous lamniform shark, Archaeolamna kopingensis, from the Pierre Shale of western Kansas, U.S.A.

ABSTRACT All previous records of the lamniform shark, Archaeolamna kopingensis, are based on isolated teeth. Here we describe a partial skeleton from the Sharon Springs Formation of the Pierre Shale Group of western Kansas, U.S.A. The specimen includes portions of the upper and lower jaws with articulated teeth. The dentition consists of two files of upper and lower anterior teeth that, together with a single file of intrabullar intermediate teeth, are housed in a dental bulla, as well as multiple files of lateral teeth, along with at least two files of lower symphysial teeth and a single file of upper symphysial teeth. The intrabullar intermediate tooth is slightly shorter than the other anterior teeth and has a median cusp with distinctive distal curvature. The dental sequence of A. kopingensis is unique among both extinct and extant lamniforms. Associated with the jaws are fragments of the neurocranium and multiple vertebral centra. A sagittal section through a centrum shows that this shark deposited 18 annual marker bands after its birth and adult size was attained by the 10th band. The robust but penetrating tooth morphology and large jaw circumference suggest that A. kopingensis likely fed upon large prey items.

From ‘third pole’ to north pole: a Himalayan origin for the arctic fox

The ‘third pole’ of the world is a fitting metaphor for the Himalayan–Tibetan Plateau, in allusion to its vast frozen terrain, rivalling the Arctic and Antarctic, at high altitude but low latitude. Living Tibetan and arctic mammals share adaptations to freezing temperatures such as long and thick winter fur in arctic muskox and Tibetan yak, and for carnivorans, a more predatory niche. Here, we report, to our knowledge, the first evolutionary link between an Early Pliocene (3.60–5.08 Myr ago) fox, Vulpes qiuzhudingi new species, from the Himalaya (Zanda Basin) and Kunlun Mountain (Kunlun Pass Basin) and the modern arctic fox Vulpes lagopus in the polar region. A highly hypercarnivorous dentition of the new fox bears a striking resemblance to that of V. lagopus and substantially predates the previous oldest records of the arctic fox by 3–4 Myr. The low latitude, high-altitude Tibetan Plateau is separated from the nearest modern arctic fox geographical range by at least 2000 km. The apparent connection between an ancestral high-elevation species and its modern polar descendant is consistent with our ‘Out-of-Tibet’ hypothesis postulating that high-altitude Tibet was a training ground for cold-environment adaptations well before the start of the Ice Age.

A new basal skunk Martinogale (Carnivora, Mephitinae) from Late Miocene Dove Spring Formation, California, and origin of New World mephitines

Abstract We describe an associated skull and lower jaws of a new species of primitive skunk, Martinogale (subfamily Mephitinae), from the late Miocene Dove Spring Formation (late Clarendonian), Kern County, California. It is also the first occurrence of this genus in the Tertiary of the West Coast of North America. The new species is among the best-preserved primitive fossil skunks and represents one of the earliest members of the New World mephitines. As the smallest skunk so far known, the new Martinogale features some of the most primitive cranial and dental morphologies in mephitines. The new information permits a phylogenetic analysis of basal taxa from North America, which suggests a New World clade for all known fossil and living taxa from North and South America. We place this New World clade in a tribe (Mephitini) of its own. New World mephitines share the following derived characters: presence of a P4 parastyle, m1 hypoconid dominant in talonid, and presence of a lingual cingulum on lower canines. We further postulate that New World skunks are the result of a single immigration event, and the new California skunk is close to the origin of the New World skunks.

A New Late Miocene Species of Sciaenid Fish, Based Primarily on an in situ Otolith from California

Abstract A new species of sciaenid, Seriphus lavenbergi sp. nov., is described from the late Miocene Yorba Member of the Puente Formation, southern California. The holotype is represented by an incomplete disarticulated skull with the right saccular (= sagitta) otolith in situ, an extremely rare occurrence. This is the earliest known geological occurrence of Seriphus and represents a second species within the genus. It is hypothesized that the ancestor of Seriphus emigrated from the Gulf Stream of the Atlantic into the Pacific via the Panama Seaway and the genus evolved entirely in the eastern Pacific.

Fossil Ceratioid Anglerfishes (Teleostei: Lophiiformes) from the Miocene of the Los Angeles Basin, California

Abstract Fossil ceratioid anglerfishes are described from the Upper Miocene (upper Mohnian) deposits of the Puente Formation, Los Angeles Basin, California. The specimens were collected from the laminated turbiditic deposits of the Yorba Member in the eastern sector of the Los Angeles Basin during the construction of a new metro rail line. Five taxa (Borophryne cf. apogon; Chaenophryne aff. melanorhabdus; Leptacanthichthys cf. gracilispinis; Linophryne cf. indica; Oneirodes sp.) belonging to two families, Linophrynidae and Oneirodidae, are described based on nine metamorphosed females. A detailed osteological analysis of the fossils has revealed that they can be tentatively assigned to extant species, suggesting that little or no relevant morphological change has characterized these taxa at least since the Late Miocene. Biogeographic considerations suggest that the Late Miocene ceratioid assemblages of the Los Angeles Basin are strikingly similar to those that currently inhabit the tropical and subtropical eastern Pacific region. From a paleoenvironmental point of view, the excellent preservation of the specimens suggests a reduced turbulence and velocity of the turbidity fluxes. Finally, the comparative study of the bathymetric ranges of the ceratioid taxa recognized in the fossil assemblage described in this paper suggests that the minimum depth of the depositional environment might be estimated at approximately 1,000 m.

DISCOVERY OF THE UPPER DENTITION OF BARBOUROFELIS WHITFORDI (NIMRAVIDAE, CARNIVORA) AND AN EVALUATION OF THE GENUS IN CALIFORNIA

ABSTRACT The family Nimravidae is a group of cat-like carnivorans that evolved sabertooth forms in parallel to Felidae. The last records of nimravids are represented by species of the North American genus Barbourofelis. Fossils of Barbourofelis found in Clarendonian North American Land Mammal Age (NALMA) deposits of California represent the western-most occurrences of the genus. Here we describe new material of Barbourofelis whitfordi from the late Miocene Dove Spring Formation (12.5–8 Ma) of the northwestern Mojave Desert, southern California, including the first known saber and confirmed upper cheek dentition of the species. Consistent with the delayed canine eruption observed in other Barbourofelis species, the newly discovered permanent cheek teeth are associated with deciduous upper canines. The upper and lower third premolars of B. whitfordi are larger in size relative to the carnassials, and less reduced in cusp morphology than other Barbourofelis species. In this regard, p3 morphology and size in B. whitfordi resemble that of the Eurasian Sansanosmilus more so than its congeneric species. The known stratigraphic range of B. whitfordi within the Dove Spring Formation spans a two-million-year period from 10.5 to 8.4 Ma. Based on a distal humerus described in this study, the record of Barbourofelis in the Dove Spring Formation now extends to the Cl1–Cl2 boundary at ∼12 Ma. A comparison of known Barbourofelis in the United States revealed that the B. morrisi—B. loveorum—B. fricki sequence might represent a single anagenetic lineage, whereas B. whitfordi represents a side lineage contemporaneous with B. morrisi during much of the Clarendonian NALMA.

First Fossil Record of Totoaba Villamar 1980 (Teleostei: Sciaenidae) Based upon Early Miocene Otoliths from California with Comments on the Ontogeny of the Saccular Otolith

Abstract A new species of the genus Totoaba (family Sciaenidae) based upon otoliths from the late early Miocene marine upper Olcese Sand, Kern County, southern San Joaquin Valley, California is described. This is the first fossil occurrence for the genus, and it is hypothesized that Totoaba evolved entirely in the eastern Pacific realm. Within the upper Olcese Sand, this species represents but one component of a complex sciaenid fauna, which could provide insight into the evolution and distribution of the family Sciaenidae. An ontogenetic series of this species is defined, and ontogenetic changes in its otoliths are discussed.