Pleistocene Horse Research Articles

Character, Age and Ecology of the Hezheng Biota from Northwestern China

Abstract The Hezheng area of Gansu Province produces the most abundant mammal fossils in China as well as the whole Eurasia, and it also produces other Cenozoic fossils of different animals and plants. Therefore, all of them are named the Hezheng Biota. Mammals are very sensitive to environmental changes, and thus the evolution of mammalian faunas in the Hezheng area reflects the strong uplift of the Tibetan Plateau during the Late Cenozoic, which dramatically affects environmental changes. In the Hezheng area, micromammals are not very rich, but some of them still are important. It is relatively uncommon that three primates are found from the Middle Miocene and the Early Pleistocene deposits. Since the Middle Miocene, carnivores have become important components in the ecosystem of the Hezheng area, and dominated in the Early Pleistocene. The Middle Miocene is a time of high diversity for Proboscidea, characterized by shovel‐tusked elephants. Perissodactyls in the Hezheng area are very abundant, especially Late Oligocene and Late Miocene rhinoceroses as well as the Late Miocene and Early Pleistocene horses. From the Middle Miocene, artiodactyls became important components of the mammalian faunas, especially bovids.

Rapid body size decline in Alaskan Pleistocene horses before extinction.

About 70% of North American large mammal species were lost at the end of the Pleistocene epoch. The causes of this extinction--the role of humans versus that of climate--have been the focus of much controversy. Horses have figured centrally in that debate, because equid species dominated North American late Pleistocene faunas in terms of abundance, geographical distribution, and species variety, yet none survived into the Holocene epoch. The timing of these equid regional extinctions and accompanying evolutionary changes are poorly known. In an attempt to document better the decline and demise of two Alaskan Pleistocene equids, I selected a large number of fossils from the latest Pleistocene for radiocarbon dating. Here I show that horses underwent a rapid decline in body size before extinction, and I propose that the size decline and subsequent regional extinction at 12,500 radiocarbon years before present are best attributed to a coincident climatic/vegetational shift. The present data do not support human overkill and several other proposed extinction causes, and also show that large mammal species responded somewhat individualistically to climate changes at the end of the Pleistocene.

Pleistocene horses (genus Equus) in the central Balkans

A review of the fossil horses of the genus Equus from the central Balkans, a mountainous area comprising Serbia and Montenegro, is presented in this paper. The time period covered by the finds is from the late Early to and including the Late Pleistocene, but the record is not complete: the dated finds are Late Pleistocene in age, while Early and Middle Pleistocene are poorly represented. The horses found resemble those from neighbouring countries from the same time period, probably showing the importance of river valleys as migration routes. The Morava River valley runs in a roughly south-to-north direction, connecting, via the Danube and Tisa River valleys the Hungarian Pannonian Plain in the north with northern Greece in the south, via the Vardar River valley in Macedonia. In Pleistocene, large mammals, including horses, probably used this route for dispersal.

Ancient latitudinal gradients of C3/C4 grasses interpreted from stable isotopes of New World Pleistocene horse (Equus) teeth

Ancient latitudinal gradients of C3/C4 grasses interpreted from stable isotopes of New World Pleistocene horse (Equus) teeth

The Pleistocene horses from Achenheim, near Strasbourg (Alsace, France), and a comparison with contemporaneous finds

The Pleistocene horses from Achenheim, near Strasbourg (Alsace, France), and a comparison with contemporaneous finds

Patterns of body size changes in fossil and living equini (Perissodacytla)

The importance of body mass prediction from several cranial, dental and appendicular variables in living Equini are studied. Relationships between the body mass changes and the ecogeographic picture of Equini evolution are also analysed. The metapodial and phalanx variables, particularly antero-posterior diameters, are better correlated with body mass than cranial variables in living Equini. Large sized species are correlated with cold climates, open habitats and/or soft soils; small ones are correlated with warm climates, more closed habitats and/or hard soils. Pleistocene horses from Europe and Africa follow an evolutionary trend opposite to their North American counterparts, from larger sized species to smaller ones. In South America the pattern of body size is different to those of the other continents. Species of Hippidion reaching large body mass, whereas some species of Euus, E. Andium, follow a diminishing trend.

Patterns of body size changes in fossil and living Equini (Perissodactyla)

The importance of body mass prediction from several cranial, dental and appendicular variables in living Equini are studied. Relationships between the body mass changes and the ecogeographic picture of Equini evolution are also analysed. The metapodial and phalanx variables, particularly antero-posterior diameters, are better correlated with body mass than cranial variables in living Equini. Large sized species are correlated with cold climates, open habitats and/or soft soils; small ones are correlated with warm climates, more closed habitats and/or hard soils. Pleistocene horses from Europe and Africa follow an evolutionary trend opposite to their North American counterparts, from larger sized species to smaller ones. In South America the pattern of body size is different to those of the other continents. Species of Hippidion reaching large body mass, whereas some species of Equus, E. andium, follow a diminishing trend.

Paleoecological Significance of Mummified Remains of Pleistocene Horses from the North Slope of the Brooks Range, Alaska

Radiocarbon dates from horse fossils found on the North Slope of Alaska show that horses did live there during the last peak glacial (Duvanny Yar Interval, Marine Isotope Stage 2). Some previous paleoecological studies have assumed the region's climate was too extreme for large mammals during the Duvanny Yar. Hoof structure suggests the Pleistocene horses survived on winter range characterized by low snowfall and/or snow removal by wind. Hoof growth rate suggests a substantial dietary volume of exposed dead grass during winter; hoof wear pattern indicates the horses were able to remain relatively sedentary, requiring neither long-distance winter migration nor constant digging through snow for food. Bones with mummified soft tissue may have been buried and preserved by wind-drifted eolian silt.

Equus lambei Hay, the Yukon Wild Horse, Not Ass

In 1917 Hay described Equus lambei, a new species of horse from the Pleistocene of Gold Run Creek, Territory. Hay compared lambei with various Pleistocene horses from North America and Asia and with the domestic horse, and believed the species to be distinct. Savage (1951) referred E. lambei to E. cf. caballus, whereas Quinn (1957) placed lambei in the genus Onager (= Hemionus or Asinus of authorssee Harington and Clulow, 1973). Recently Harington and Clulow (1973) and Harington (1978), following Quinn (1957), referred to lambei as the Yukon wild ass, E. (Asinus) lambei. From Hay's (1917) measurements on the type skull, from photographs of skulls and jaws, and from measurements of limb bones in Harington and Clulow (1973), it is evident that E. lambei is a caballoid horse, not an ass. The closest resemblance to lambei is shown by the Recent Mongolian horse, E. caballus przewalskii, now probably extinct in the wild. Measurements of the type skull (Hay, 1917) show caballoid proportions: the length from the rear of the hard palate to the notch in the vomer is much shorter than the length from the notch in the vomer to the front of the foramen magnum (see Eisenmann, 1980). The skull is relatively broad because of its small size and the negatively allometric growth of breadth in relation to length in the skull of horses (e.g., Forsten, 1982). Harington and Clulow (1973) figured the type jaw with the cheek teeth of E. lambei. The cheek teeth are typically caballoid, with a wide, U-shaped, lingual groove between the metaconid and metastylid, instead of a V-shaped groove as in the asses, or a Vor U-shaped groove as in the hemiones. The molars show a shallow ectoflexid; although more frequent in asses and hemiones, this feature is not uncommon in E. przewalskii (Eisenmann, 1981). The long protocone of the upper cheek teeth strengthens the impression that this is a horse, rather than ass or even a hemione. The metapodials of lambei (Harington and Clulow, 1973) are slender, comparable to those of E. przewalskii (Eisenmann, 1979). The metapodials, with the exception of the specimen LUM 1.106 referred to as E. (Asinus) kiang (Harington and Clulow, 1973), are shorter and more massive than those of the hemiones (Eisenmann, 1979). The single proximal phalanx is longer than phalanges of E. przewalskii, but when plotted in a discriminant field (see Davis, 1982) falls in among bones of the latter, while differing from those of asses and hemiones. The bone closely resembles proximal phalanges of E. caballus lenensis from the late Pleistocene of Siberia (Veresagin and Lasarev, 1977). The proportions and morphology show that E. lambei is a horse, not an ass or a hemione, thus supporting Savage's (1951) conclusion as to its affinities, rather than that of Quinn (1957) or Harington and Clulow (1973). In size and proportions E. lambei resembles E. caballus przewalskii (see also Veresagin and Lasarev, 1977). The occurrence of a small, slender, caballoid horse in the late Pleistocene of eastern Beringia is interesting and furnishes yet another species in common with Eurasia. In western Beringia there occurred at the same time the equally small, but slightly more robust horse, E. caballus lenensis (Sher, 1971; Vangengeim, 1961; Veresagin and Lasarev, 1977). In North America the horse became extinct at the end of ere had been previous anecdotal evidence of bush dogs in savan a west of Tuparro, but this was the i st confirmation of the species' presence i the park. 422 Vol. 67, No. 2

How and Why Horses Open Crescentia alata Fruits

Costa Rican range horses break the hard, ripe fruits of Crescentia alata with their incisors and swallow the small seeds imbedded in the sugar-rich fruit pulp. The seeds survive the trip through the horse and germinate in large numbers where horses have defecated. The ripe fruits required about 200 kg pressure to break, and fruits that were too hard for the horses to break required 272 to 553 kg to break. Unbreakable fruits had thicker hulls, and their presence provides an example of how a fruit trait may serve to spread seeds among more than one kind of large dispersal agent. Crescentia alata (Bignoniaceae, 'jicaro') is a common and widespread shrubby tree in the lowland, grassy habitats o,f the Pacific side of Central America. It is native to this area, yet in many places the large, cauliflorous, hard, and indehiscent fruits (fig. la) fall to the ground below the tree, ripen over the next three-five weeks, and rot without ever being touched by a potential dispersal agent. The many small, soft seeds imbedded in the sugar-rich pulp die without germinating in the unopened fruits. This fate is typical even in National Parks containing an apparently normal fauna of large mammals. These observations bring to mind the question of what animal is the normal dispersal agent of C. alata and how does this agent eat such a large fruit? The answer is found in habitats where horses have access to C. alata trees. The brittle, ripe fruits are bitten open by range horses and the black, moist, sweet, and seed-rich contents are swallowed after only slight chewing. Many of the seeds survive the trip through the horse and shortly thereafter germinate in the remains o,f the dung (fig. le). The modern, introduced horse (Equus caballus) is a dispersal agent of C. alata, so, presumably, the Pleistocene horse that undoubtedly occupied C. alata habitats until 10,000 years ago was also (Janzen and Martin 1982). In Santa Rosa National Park, as elsewhere in the semi-forested pastures in the lowlands of Pacific coastal Costa Rica, range horses are avid consumers of the contents of ripe fruits of C. alata. Here I describe in detail how they do it, ask how much effort it requires, and consider the significance of the fruits that are so hard that horses cannot break them.

Late Pleistocene Horses of Dry Cave, Eddy County, New Mexico

Equus conversidens Owen, E. niobrarensis Hay, E. occidentalis Leidy referred, E. scotti Gidley referred, and a small zebrine horse are recognized from late Pleistocene deposits of Dry Cave, southeastern New Mexico. Equus midlandensis Quinn is synonymized with E. niobrarensis ; New Mexican specimens previously recognized as E. scotti are identified as E. niobrarensis . Cluster analysis of measurements of single elements, acting on matrices of taxonomic distances, appears to allow assignment of intermingled elements to species more successfully than do traditional comparative methods. Cluster analysis based on correlation matrices of limb proportions indicates close similarity of E. niobrarensis to E. przewalskii Poliakoff. Dental characters and cluster analysis suggest that E. conversidens belongs to the subgenus Hemionus or was derived from that subgenus.

Paleopathology: Exostoses of the Third Metacarpal in Pleistocene Horses from the Yukon Territory

Two third metacarpals from extinct Yukon Pleistocene horses display pathological exostoses. One specimen is from the Yukon wild ass (Equus (Asinus) lambei) of probable late Pleistocene age; the other is from a large horse like Equus (Plesippus) verae, which may be of early middle Pleistocene age or somewhat later.

A. Rare Case of Articulated Transverse Processes in a Lumbar Vertebra of the Pleistocene Horse Equus scotti

Articulated transverse processes are noted on the first lumbar vertebra of a mounted skeleton of a Pleistocene horse Equus scotti from Rock Creek, Texas. This unusual situation is attributed to aberrant genetic programming.

A climatic sequence from two Nevada caves

Fishbone and Guano caves, Pershing County, cut in granite by pluvial Lake Lahontan, were exposed for animal and human occupation about the time of the Two Creeks interstadial. Aside from the usual irregularities due to habitation, modern disturbance has made it impossible to secure continuous stratigraphy in the samples furnished by P.C. Orr. However, by combining radiocarbon dates and study of the sediments as well as statistical analysis of the included pollen, a profile consonant with known climatic history since about 15,000 years B.P. has been obtained. A climax of aridity occurred between 6000 and 7000 B.P. shortly following the undoubted evidence of Pleistocene horse and camel. A less extreme aridity developed about 3200 B.P. Interesting evidence of climatic change before 15,000 is present, but its chronology must await study of cores from the sediments of Lake Winnemucca.

ON CENOZOIC VERTEBRATES IN KOREA

Cenozoic fossil mammals, relatively rare in Korea, were first discovered there in 1915 by K. Jimbo and identified as possibly Pleistocene horse and rhinoceros remains. Subsequently, seven mammalian species of Eocene Carnivora and Perissodactyla were found in the Pongsan coal fields. Miocene fossils discovered include 4 vertebrate species; the most extensive occurrences are represented by the Pleistocene. Of 19 mammalian species, 15 were taken from a single terrace deposit. Correlation with other far-eastern foSsil localities is attempted where sufficient data was available. Tentative identifications are made of an elephantine tooth and a sabre-toothed tiger, both Pleistocene. Specimens from Tungryong-gul limestone cave are probably too recent to be properly designated fossils. D. D. Fisher