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Home , Deng Tao, Hispanotherium, Hyracodontidae, Iranotherium, Paraceratherium, Ronzotherium

Vol.24 No.2 2010 Paleomammalogy

Linxia Basin: An Ancient Paradise for Late in North

DENG Tao * Institute of Vertebrate and Paleoanthropology, CAS, Beijing 100044

he Linxia Basin is located and sometimes partially articulated several hundred of the late on the triple-junction of the bones of large , which often Cenozoic rhinoceroses are known from Tnortheastern Tibetan Plateau, occur in dense concentrations. Many the Linxia Basin. In addition, more western Qinling Mountains and the new of the Late abundant limb bones and isolated teeth Loess Plateau. The basin is filled with Dzungariotherium fauna, the Middle of rhinoceroses are found in this basin, 700−2000 m of late Cenozoic deposits, Platybelodon fauna, the Late especially from the Late Miocene mainly red in color and dominated by Miocene fauna, and the Early red clay deposits. Rhinoceroses were lacustrine siltstones and mudstones, and Pleistocene Equus fauna have been over 70% in diversity during the Late the Linxia sequence represents the most described from the Linxia Basin since Oligocene, and they were dominant in complete and successive late Cenozoic 2000, including rodents, lagomorphs, population during the Late Miocene. section in China. The localities in the primates, carnivores, proboscideans, In the Middle Miocene and Early Linxia Basin are notable for abundant, perissodactyls and artiodactyls. Pleistocene faunas, rhinoceroses were relatively complete, well-preserved, Among these mammalian , important members.

Late Oligocene

The Late Oligocene fauna of findings in (Qiu and Wang, is estimated at 24 tons, and another the Linxia Basin comes from the 2007). Their giant size and some species yagouense sandstones of the Jiaozigou Formation. features so distinctive from the living at 22 tons (Deng, 2009). In this At least eight species of rhinoceroses rhinoceroses have attracted much fauna, other rhinoceroses include were found from this fauna, including attention not only from specialists, but gen. et sp. indet., two forms of giant rhinos. The giant also from the public. According to Ardynia sp., A. altidentata, Allacerops rhinos, the largest land mammals, the specimens from the Linxia sp., sp., and Aprotodon are an endemic group almost Basin, the body weight of the giant lanzhouensis. Rhinoceroses dominated exclusively to Asia, with only sparse rhino Dzungariotherium orgosense the Late Oligocene fauna in the Linxia

*Correspondences should be addressed at [email protected].

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Basin, where predators were relatively the global range, a great regression south and north sides of the Tibetan primitive, with creodonts represented took place at 30 Ma, with nearly Plateau indicate that the uplift of by Megalopterodon (Fig. 1) only simultaneous disappearance of the the plateau had no enough height to rarely seen. Turgai Strait. The first uplift of prevent dispersals of huge mammals, In the Siwalik area on the the “Tibetan Plateau” might have therefore giant rhinos, aprotodons and southern border of the Tibetan occurred in a large area at the latest chalicotheres were free to migrate Plateau, there was also distribution of Early Oligocene. On the other hand, between the south and north sides of giant rhinos in the Late Oligocene. In the discoveries of giant rhinos on the the “Tibetan Plateau.”

Fig.1 A habitat of giant rhinos during the Late Oligocene. In the foreground, a creodont (Megalopterodon sp.) is attacking a giant rhino calf (Dzungariotherium orgosense). The top right corner shows the comparison of the upper second molars between D. orgosense (left) and Ardynia altidentata (right) to the same scale.

Middle Miocene

The Middle Miocene mammals H. matritense was found in Spain, Turkey. Alicornops laogouense is a of the Linxia Basin were collected Portugal, and in Europe, and middle-sized acerathere, and its from the sandstones or conglomerates Turkey, Pakistan, , and is the largest of the . The origins of the Dongxiang and Hujialiang China in Asia. H. matritense is small- of the and Alicornops formations. The fossils of this fauna sized, with one nasal horn, and it lineages may be in southwestern are represented by the shovel- has subhypsodont cheek teeth with Europe. With the discovery of H. tusked Platybelodon, and very thick cement cover. Alicornops matritense and A. laogouense in the the rhinoceroses Hispanotherium is distributed widespread in Europe Linxia Basin, it appears that they matritense and Alicornops laogouense during MN 6-10, and it was found dispersed from western Europe are important members. In , from the Middle Miocene strata in through eastern Europe, western Asia

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and southern Asia, to the Far East. somewhat different from that of its In the Middle Miocene, Platybelodon H. matritense in Europe was European counterparts. A large number was found from many localities on the considered to live in dry and warm of fossils of Platybelodon, which north side of the Tibetan Plateau, while settings because of its hypsodont teeth favored habitats near water, were found this proboscidean form has no trace in with thick cement cover and slender with H. matritense and A. laogouense the Indian subcontinent on the south, limbs. In the Linxia Basin, the fossils in the Linxia Basin. This shows which suggested that the uplift of the of H. matritense came from fluvial that lakes and rivers were abundant Tibetan Plateau by this period was high grey-yellowish sandstones with gravel, in the environment in which these enough to baffle interchanges of large and its paleoenvironment in China was rhinoceroses lived (Deng, 2003, 2004). mammals.

Late Miocene

The Late Miocene fauna of the Linxia Basin was found from the red clays of the Liushu Formation and characterized by the three-toed horse Hipparion. In this fauna, the was dominant in population, and other rhinoceroses showed the largest diversity of this group during the geological history of the Linxia Basin, including hezhengensis, Shansirhinus ringstroemi, Chilotherium primigenius, C. wimani, C. anderssoni, Iranotherium Fig.2 The fossil black rhino (Diceros gansuensis) from the Linxia Basin, the first discovery morgani, Parelasmotherium simplym, P. of this lineage from East Asia, is the ancestor form of the extant African black rhino (D. bicornis). Two skulls (left: D. gansuensis; right: D. bicornis) are shown herein to exhibit linxiaense, Ningxiatherium euryrhinus, the morphological similarities and differences between them. Dicerorhinus ringstroemi, and Diceros gansuensis. Chilotherium wimani is the most teeth, and its skull is particularly living black rhino D. bicornis (Fig. 2). abundant in the Linxia Basin. elongate and dorsally concave. The Lacking fossils, the early evolutionary Remains of C. wimani are in fact sexually dimorphic characters of the history of the African rhinoceroses found practically everywhere in the male and female skulls of I. morgani remained poorly known until quite middle and upper parts of the Liushu show that the male skull is more recently. Diceros gansuensis is the Formation. C. wimani is a middle- massive, with stronger zygomatic first fossil species of the Diceros sized rhinoceros without any horn, arches. These features, especially the lineage ever found in East Asia, and its particularly wide mandibular huge nasal horn, could be used for and this discovery supports that the symphysis has two huge tusk-like defense or competition for mates. I. African rhinoceroses were split up into . Iranotherium morgani is the morgani was a polygynous grazer its two living genera already at the only known rhinoceros with a rugosity lived in an open steppe. It is likely to beginning of the Late Miocene (Deng for larger masseteric and temporalis have first appeared in northwestern and Qiu, 2007). In the Late Miocene, musculature on each zygomatic China, later dispersing westward the Tibetan Plateau became a more arch of the male individual, which to central Asia (Deng, 2005). The sufficient barrier for dispersals. suggests that this species was sexually skull, mandible and teeth of Diceros Components of the Hipparion fauna at dimorphic. I. morgani has a large size gansuensis from the Linxia Basin high-level taxa were similar to those with a huge nasal horn and hypsodont are distinct from those of the African of the modern mammalian fauna.

Early Pleistocene

The Early Pleistocene fauna number of carnivore species is high, of herbivores. The representative Equus of the Linxia Basin comes from the and their specimens are particularly eisenmannae is a giant true horse, and Wucheng Loess. In this fauna, the numerous, even outnumbering the total its size implies that it inhabited a cold

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Fig.3 The ecological environment of the Early Pleistocene fauna of the Linxia Basin. The foreground shows a skull of the earliest known woolly rhino ( nihowanensis) collected from the Wucheng Loess and the reconstruction of this species. This discovery indicates that woolly rhinos might have originated from north China.

environment with a vegetation of tough rhino, which was distributed widely in to deposit, covering only small tops of grasses. This habitat was suitable for the north Eurasia during the Late Pleistocene, the low mountains in this area. In the ancestor of the woolly rhino, Coelodonta is affirmed from northern China at the Early Pleistocene, the Tibetan Plateau nihowanensis, which was first found from beginning of the Quaternary (Deng, was already uplifted considerably. The Nihewan, Hebei, but its material included 2008). strong uplift of the Tibetan Plateau only a milk row. A complete adult Since the beginning of the must have caused great environmental skull with mandible and a partial juvenile Quaternary, the climate had become changes in the Linxia Basin. A skull of C. nihowanensis were found cold and dry, and the diversity of stronger winter monsoon system from the earliest loess deposits in the mammals had reduced in the Linxia and a higher continental desiccation Linxia Basin. It was clearly considered basin. Taken as a whole, the Linxia occurred during this time span. The a primitive species of woolly rhino, and Basin should have been predominantly deteriorated climatic conditions in this implied that the woolly rhino actually an area of steppe, mixed with shrub area, such as lower temperature and originated in Asia. They are by far the and bush areas, occasionally with less precipitation, are also reflected in earliest remains of the woolly rhino in the small patches of forest and woodland the loess deposits, which are thick, but world, and the origination of the woolly (Fig. 3). Loess might have just started without marked paleosols.

References

Deng T, 2003. New material of Hispanotherium matritense (Rhinocerotidae, Perissodactyla) from Laogou of Hezheng County (, China), with special reference to the Chinese Middle Miocene elasmotheres. Geobios, 36: 141–150. Deng T, 2004. A new species of the rhinoceros Alicornops from the Middle Miocene of the Linxia Basin, Gansu, China. Palaeontology, 47: 1427–1439. Deng T, 2005. New discovery of Iranotherium morgani (Perissodactyla, Rhinocerotidae) from the Late Miocene of the Linxia Basin in Gansu, China and its . Journal of Vertebrate Paleontology, 25: 442–450. Deng T, 2008. Comparison between the woolly rhino’s forelimbs from Longdan, northwestern China and Tologoi, Transbaikalian region. Quaternary International, 179: 196–207. Deng T, 2009. Late Cenozoic environmental change in the Linxia Basin (Gansu, China) as indicated by mammalian cenograms. Vertebrata PalAsiatica, 47: 282–298. Deng T, Qiu Z X, 2007. First discovery of Diceros (Perissodactyla, Rhinocerotidae) in China. Vertebrata PalAsiatica, 45: 287–306. Qiu Z X, Wang B Y, 2007. Paracerathere fossils of China. Palaeontologia Sinica, New Series C, 29: 1–396.

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