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123 New Oligocene Primates from China Highlight Ancient Climate Vol.30 No.2 2016 Science Watch Earth Sciences New Oligocene Primates from China Highlight Ancient Climate Change as Possible Evolution Filter rofound environmental and These newly discovered fossil anthropoids migrate to Africa. It was faunal changes are associated primates were collected via careful on that continent 200,000 years ago Pwith climatic deterioration excavation and screen washing at the that humans arose. during the Eocene-Oligocene Lijiawa fossil site at the upper part The transition between the transition (EOT) roughly 34 million of Caijiachong Formation, Yuezhou Eocene and Oligocene periods was years ago. Primates are among the Basin, Yunnan Province, China. The marked by distinct cooling. This most environmentally sensitive of Lijiawa fossil site has yielded more change in climate drove a retraction all mammals. Reconstructing how than 10 mammal taxa that indicate of primates globally. Comparing the Asian primates responded to the an early Oligocene age. Researchers composition of the early Oligocene EOT, however, has been hindered by described 10 previously unknown primate faunas from Yunnan and a sparse record of Oligocene primates primates represented by fossil teeth, Pakistan with later Eocene Asian on that continent. jaws and a few other bones, helping primate faunas known from China, In a study published May to fill the gap in the record of Asian Myanmar and Thailand, researchers 6 in Science, Dr. NI Xijun at the primate evolution. revealed that surviving this Eocene- Institute of Vertebrate Paleontology The primate lineage that led to Oligocene evolutionary filter entailed and Paleoanthropology (IVPP), monkeys, apes and people, called a high degree of taxonomic and Chinese Academy of Sciences and anthropoids, originated in Asia, with ecological selectivity. his team reported the discovery of their earliest fossils dating from 45 Later Eocene primate a diverse primate fauna from the million years ago. Only later, about assemblages in China, Myanmar, early Oligocene of southern China. 38 million years ago, did some and Thailand tend to be dominated, In marked contrast to Afro-Arabian Oligocene primate faunas, this Asian fauna is dominated by strepsirhines. There appears to be a strong break between Paleogene and Neogene Asian anthropoid assemblages. Asian and Afro-Arabian primate faunas responded differently to EOT climatic deterioration, indicating that the EOT functioned as a critical evolutionary filter constraining the subsequent course of primate evolution across the Old World. This study provides a deeper understanding of a pivotal moment in the evolution of primates, Fig. 1 Diverse primates from the early Oligocene of Yunnan Province, China. (A) the group that eventually gave rise to Yunnanadapis folivorus, (B) Yunnanadapis imperator, (C) Laomaki yunnanensis, (D) people. Gatanthropus micros, (E) Oligotarsius rarus, (F) Bahinia banyueae. (Image by NI Xijun) Bulletin of the Chinese Academy of Sciences 123 BCAS Vol.30 No.2 2016 Earth Sciences Institute and co-author of the study. Dynamic changes to the Asian physical environment during the interval spanning the EOT included progressive retreat of the Paratethys Sea from central Asia, continued uplift of the Tibetan-Himalayan orogen, and opening of the South China Sea. “Africa was not immune to global climatic changes across the EOT, but it did not experience the dramatic tectonic and paleogeographic alterations that characterized Asia at this time”, said LI Qiang of IVPP, also co-author of the study: “It is tempting to attribute the different patterns of turnover in Asian and African primate faunas across the EOT to local changes in vegetation and paleoenvironment, but current evidence is not sufficient to rule out the possibility that random Fig.2 The Eocene-Oligocene transition (EOT) functioned as a critical filtering episode processes may have also played a during the evolutionary history of primates, leading to more lemur-like primates in Asia, and driving more anthropoids to emerge in Afro-Arabia. (Image by NI Xijun) substantial role.” “We have so many primates from the Oligocene at this particular site both in terms of taxonomic richness “The EOT functioned as a in China because it was located far and numerical abundance, by stem critical evolutionary filter during the enough to the south that it remained anthropoids belonging to the families evolutionary history of primates,” warm enough during that cold, dry Eosimiidae and Amphipithecidae. said lead author NI Xijun of IVPP: time that primates could still survive In stark contrast, only one of the “Before the temperatures dropped, there,” said Beard. They crowded six primates known from the early Asia’s primates were dominated into the limited space that remained Oligocene of Yunnan is anthropoid. by anthropoids. Afterward, they available to them. Like most of today's Three of five primate species were dominated by lemur-like primates, they were tropical tree- documented from the late early primates, with the monkey-like dwellers. The lone anthropoid in the Oligocene of Pakistan are anthropoids, ones decimated.” The EOT climatic group, a small, monkey-like primate but even in this case, the anthropoid deterioration may be the reason named Bahinia banyueae, probably taxa known from Pakistan differ from why apes and people emerged in resembled some of today's smaller their contemporary African relatives in Africa even though anthropoids first South American monkeys such as being relatively small-bodied. appeared in Asia. marmosets, and its teeth suggest its However, Late Eocene–early “We had a lot of evidence diet was mainly fruits and insects. Oligocene primates from Afro-Arabia previously that the earliest anthropoids This project has been supported show a very different pattern of originated in Asia. The Eocene- by the Strategic Priority Research taxonomic selectivity in response to Oligocene climate crisis virtually Program of CAS, the National Basic the EOT. There, very few strepsirhines wiped out Asian anthropoids, so the Research Program of China, the (none of which were large) survived only place where could they have CAS Hundred-Talent Program, the the EOT, whereas anthropoids evolved to become later monkeys, National Natural Science Foundation diversified both taxonomically and apes and humans was Africa,” said of China, and the U.S. National ecologically, and became dominant in Christopher Beard, senior curator at Science Foundation. Afro-Arabian regions. the University of Kansas’ Biodiversity (By CHEN Pingfu) 124 Bulletin of the Chinese Academy of Sciences.
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