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New discovery fills long-missed gap in evolutionary history

New discovery fills long-missed gap in evolutionary history
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Upper jaw of Yuanmoupithecus infant

The infant’s upper jaw of Yuanmoupithecus. Photo credit: Terry Harrison, NYU Department of Anthropology

The oldest gibbon fossil was discovered in southwest China.

The earliest fossil gibbon has been found by a team of researchers, filling a long-missed evolutionary gap in ape history.

The study, published in Journal of Human Evolutionfocuses on the hylobatid family, which includes 20 species of living gibbons found throughout tropical Asia from northeastern India to Indonesia.

“Fossil remains of hylobatids are very rare, and most specimens are isolated teeth and fragmented jawbones found in caves in southern China and Southeast Asia, no more than two million years old,” explains Terry Harrison, professor of anthropology at the New York University and one of the authors of the paper. “This new find expands the fossil record of hylobatids up to 7 to 8 million years ago and specifically improves our understanding of the evolution of this ape family.”

The fossil, found in the Yuanmou area of ​​Yunnan Province in southwest China, is of a small monkey named Yuanmoupithecus xiaoyuan. Analysis of the study focused on the teeth and skull samples from Yuanmoupithecusincluding an upper jaw of a young child who was less than two years old at the time of his death.

Excavation near Leilao Village in Yunnan

An excavation site near Leilao Village in Yunnan, one of the places where Yuanmoupithecus Remains have been found. Photo credit: Terry Harrison, NYU Department of Anthropology

Using the size of the molars as a guide, Yuanmoupithecus It has been estimated to be close in size to modern-day gibbons, weighing around 6 kilograms – or about 13 pounds.

“The teeth and underside of Yuanmoupithecus are very similar to those of modern-day gibbons, but in some features the fossil species was more primitive, indicating that it is the ancestor of all living species,” notes Harrison, part of the NYU Center for the Study of Human Origins.

Ji discovered the child’s upper jaw during a field survey, and by comparing it with modern gibbon skulls preserved at the Kunming Institute of Zoology, he was able to identify it as a hylobatid. In 2018, he invited Harrison and other colleagues to work on specimens collected over the past 30 years and housed at the Yunnan Institute of Cultural Relics and Archeology and the Yuanmou Man Museum.

“The remains of Yuanmoupithecus are extremely rare, but with care it was possible to recover enough specimens to determine that the fossil Yuanmou monkey is indeed a close relative of the living hylobatids,” notes Harrison.

That Journal of Human Evolution A study has shown that too Kapi ramnagarensiswhich is claimed to be an earlier species of hylobatid, based on a single isolated fossil molar from India, is finally not a hylobatid but a member of a more primitive group of primates not closely related to modern-day great apes.

“Genetic studies suggest that the hylobatids diverged from the lineage that led to great apes and humans about 17 to 22 million years ago, so there’s still a 10-million-year gap in the fossil record that needs to be filled,” warns harrison . “With continued exploration of promising fossil sites in China and elsewhere in Asia, we hope that additional discoveries will help fill in these critical gaps in hylobatid evolutionary history.”

References: “The Earliest Hylobatids from the Late Miocene of China” by Xueping Jia, Terry Harrison, Yingqi Zhang, Yun Wub, Chunxia Zhang, Jinming Hui, Dongdong Wua, Yemao Hou, Song Li, Guofu Wang, and Zhenzhen Wang, September 13 2022 , Journal of Human Evolution.
DOI: 10.1016/j.jhevol.2022.103251

The study was funded by the National Natural Science Foundation of China, the Yunnan Natural Sciences Foundation and the Strategic Priority Research Program of the Chinese Academy of Sciences.

The researchers also gained access to the skeletal and paleontological collections at the American Museum of Natural History in New York and the Smithsonian Institution’s National Museum of Natural History in Washington DC as part of their study.

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