The cranium of the fossil juvenile ape found at a Miocene site in Yunnan Province, China. (Credit: Denise Su/Cleveland Museum of Natural History)
Posted by Vicki Fong-Penn State on September 9, 2013
A 6-million-year-old ape cranium found in China may offer a clearer picture of the end of the Miocene, a time when apes had become extinct in most of Eurasia.
Juvenile crania of apes and hominins are extremely rare in the fossil record, especially those of infants and young juveniles. This cranium is only the second relatively complete cranium of a young juvenile in the entire Miocene—23 million to 5 million years ago—record of fossil apes throughout the Old World, and both were discovered from the late Miocene of Yunnan Province.
Shuitangba, the site from which it was recovered, has also produced remains of the fossil monkey, Mesopithecus, which represents the earliest occurrence of monkeys in East Asia.
"The fossils recovered from Shuitangba constitute one of the most important collections of late Miocene fossils brought to light in recent decades because they represent a snapshot from a critical transitional period in earth history," says Nina Jablonski, a co-author and Distinguished Professor of Anthropology at Penn State University. The paper detailing the discovery is available online in the Chinese Science Bulletin.
"The ape featured in the current paper typifies animals from the lush tropical forests that blanketed much of the world's subtropical and tropical latitudes during the Miocene epoch, while the monkey and some of the smaller mammals exemplify animals from the more seasonal environments of recent times."
Another member of the research team and co-author, Jay Kelley of the Institute of Human Origins at Arizona State University, says the preservation of the new cranium is excellent, with only minimal post-depositional distortion. "This is important because all previously discovered adult crania of the species to which it is assigned, Lufengpithecus lufengensis, were badly crushed and distorted during the fossilization process," Kelley says.
"In living ape species, cranial anatomy in individuals at the same stage of development as the new fossil cranium already show a close resemblance to those of adults. Therefore, the new cranium, despite being from a juvenile, gives researchers the best look at the cranial anatomy of Lufengpithecus lufengensis. Partly because of where and when Lufengpithecus lived, it is considered by most to be in the lineage of the extant orangutan, now confined to Southeast Asia but known from the late Pleistocene of southern China as well."
The researchers noted, however, the cranium shows little resemblance to those of living orangutans, and in particular, shows none of what are considered to be key diagnostic features of orangutan crania. Lufengpithecus therefore appears to represent a late surviving lineage of Eurasian apes, but with no certain affinities yet clear.
The survival of this lineage is not entirely surprising since southern China was less affected by climatic deterioration during the later Miocene that resulted in the extinction of many ape species throughout the rest of Eurasia. The researchers are hopeful that further excavations will produce the remains of adult individuals, which will allow them to better assess the relationships among members of this lineage as well as the relationships of this lineage to other fossil and extant apes.
"In addition to the ape, we have recovered hundreds of specimens of other animals and plants," says study co-author Denise Su, curator of paleobotany and paleoecology at the Cleveland Museum of Natural History.
"We are looking forward to going back to Shuitangba next year to continue fieldwork and, hopefully, find more specimens of not only the ape but other animals and plants that will tell us more about the environment. Given what we have recovered so far, Shuitangba has great potential to help us learn more about the environment in the latest part of the Miocene in southern China and the evolution of the plants and animals found there."
The National Science Foundation, Bryn Mawr College, American Association of Physical Anthropologists, the Yunnan National Science Foundation, the Zhaotong government, National Basic Research Program of China, and the National Natural Science Foundation of China supported this project.
Source: Penn State University