Sukuan Hou

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 New Method of Tooth Mesowear and a Test of it on Domestic Goats

Mesowear III is a new form of mesowear that uses separately the mesial and distal surfaces of enamel band 2 of the upper second molar to differentiate between a browsing and a grazing diet. The enamel band of browsers is flat and planar, in grazers it contains gouges and sub-facets which eventually become round. Mesowear III scores these shapes on a scale 1–4; score 1 represents the typical browser and score 4 represents a typical grazer. Differences in diet can also be studied by observing the junction between the mesial and distal side of the enamel band (j point); the j point is sharper and well defined in browsers, while it is rounder or non-existent in grazers. Wild browsers, grazers, and mixed feeders separate well using mesowear III. The wild taxa data were similar to mesowear III of experimental goats that were fed a controlled grazing or browsing diet (species of plants known). In addition, the browsing versus the grazing goat mesowear III signal becomes more distinct from each other by 40 days of feeding. Mesowear III so far gives a finer signal than previous mesowear (I and II).

Sexual dimorphism in perissodactyl rhinocerotid Chilotherium wimani from the late Miocene of the Linxia Basin (Gansu, China)

Sexual dimorphism is reviewed and described in adult skulls of Chilotherium wimani from the Linxia Basin. Via the analysis and comparison, several very significant sexually dimorphic features are recognized. Tusks (i2), symphysis and occipital surface are larger in males. Sexual dimorphism in the mandible is significant. The anterior mandibular morphology is more sexually dimorphic than the posterior part. The most clearly dimorphic character is i2 length, and this is consistent with intrasexual competition where males invest large amounts of energy jousting with each other. The molar length, the height and the area of the occipital surface are correlated with body mass, and body mass sexual dimorphism is compared. Society behavior and paleoecology of C. wimani are different from most extinct or extant rhinos. M/F ratio indicates that the mortality of young males is higher than females. According to the suite of dimorphic features of the skull of C. wimani, the tentative sex discriminant functions are set up in order to identify the gender of the skulls.

Neogene integrative stratigraphy and timescale of China

The widely exposed Chinese Neogene terrestrial deposits provide the best circumstance for the establishment of an accurate chronostratigraphic system of Eurasia, and the rapidly evolved mammalian fossils contribute efficiently to the division and correlation of Asian Neogene strata. A uniform Neogene biostratigraphic framework for China has already been established, with seven mammalian ages named. With a developed stratigraphic basis for the geochronologic “ages”, seven chronostratigraphic “stage” have been established for the Chinese Neogene terrestrial strata, namely the Miocene Xiejian, Shanwangian, Tunggurian, Bahean, and Baodean stages, and the Pliocene Gaozhuangian and Mazegouan stages. Based on a series of research achievements, refined biostratigraphic, paleomagnetic and isotopic methods were combined and applied to continuous sections, and a Chinese Neogene chronostratigraphic sequence with accurate geological ages was established and improved in recent years. The lower boundaries of most of the stages could be correlated with those of the marine stages in the International Chronostratigraphic Chart, except the Tunggurian Stage, which is correlated with the European land mammal age. The biostratigraphic markers of the Chinese Neogene stages are usually first appearance of a single taxon, some representing regional species replacement, others indicating intercontinental migration of certain taxa. Candidate stratotype sections have been proposed for all the Chinese Neogene stages according to the principle and rule of modern stratigraphy, and other Chinese Neogene strata in different regions are comprehensively correlated.

Palaeoenvironment examination of the terminal Miocene hominoid locality of the Zhaotong Basin, southwestern China, based on the rhinocerotid remains

Abstract Anatomic modification in evolution process of mammals was closely correlated with the environmental changes, and become the powerful evidence for reconstructing the palaeoenvironment shaped their evolution. Rhinocerotid fossils are important indicators of the ecosystems inhabited by the mammalian faunas. Here, we first described remains of two rhinocerotids from the terminal Miocene Zhaotong Basin, the most recent hominoid locality in South China, including Acerorhinus lufengensis and Rhinocerotini gen. et sp. indet. New remains of A. lufengensis display a short crochet and antecrochet, expanded lingual cones, and rounded labial wall of the trigonid and talonid. These characteristics demonstrate its feeding habits of grazing brush and high grass. The limb bones of Rhinocerotini gen. et sp. indet. enable to live in an open habitat in having the following characteristics: the Mc II facet of Mc III is large, oval, flattened, and nearly vertical in direction; the femur exhibits a very large trochanter tertius and two nearly parallel asymmetrical ridges of the distal patella trochlea. The rhinocerotid fossils described herein provide a substantial evidence of the presence of mosaic environment, and the grassland should patches within or along the margin of the forest in the terminal Miocene Shuitangba locality.