Many of the ancient primate finger and toe bones are no bigger than a grain of rice. Many of the primate species they belonged to were about the size of a mouse. Photo Northern Illinois University
Nov. 9 (UPI) -- Scientists have detailed the discovery of some 500 ancient primate toe and finger bones. The tiny fossils were recovered from China and described this week in the Journal of Human Evolution.
"The fossils are extraordinarily small, but in terms of quantity this is the largest single assemblage of fossil primate finger and toe specimens ever recorded," Dan Gebo, a researcher at Northern Illinois University, said in a news release.
Many of the bones are barely larger than a grain of rice, but they have offered scientists a glimpse into the lives of the earliest primates. The bones represent a variety of primate families and at least 25 different early primate species, including the first known anthropoid, Eosimias. Three of the fossils represent newer, more advanced anthropoid species.
The earliest primates -- hailing from the mid-Eocene period, around 45 million years ago -- ranged in size from 10 to 1,000 grams. They occupied the tree canopies of ancient jungles, eating fruits and insects. All of the fossils reveal an ability to grasp with both hands and feet, a prerequisite for life among the tree tops.
"The new study provides further evidence that early anthropoids were minuscule creatures, the size of a mouse or smaller," Gebo said. "It also adds to the evidence pointing toward Asia as the initial continent for primate evolution. While apes and fossil humans do come from Africa, their ancestors came from Asia."
The bones were recovered from a quarry near Shanghuang, a village in the south of Jiangsu Province, which is positioned along the central portion of China's east coast. The limestone in the quarry dates back to the Triassic, some 220 million years ago, when the first dinosaurs emerged. But erosion left fissures in the rock, which captured layers of fossil-rich sediment dated to the Eocene, when mammals begin to flourish in the absence of the dinosaurs.
"Because of commercial exploitation of the quarry site, the fossil-bearing fissure-fillings at Shanghuang are now exhausted," said Christopher Beard, a paleontologist at the University of Kansas. "So, the fossils that we currently have are all that will ever be found from this site."
But researchers continue to sift through the remarkable paleontological record that was recovered from the quarry over the last few decades.
The diversity of primate species found at Shanghuang is unusual, and researchers hope their ongoing analysis can help scientists better understand the evolution of primate anatomy, including the unique fingers shared by all modern anthropoids, or higher primates.
"These are the earliest known examples of those narrow fingers and toes that are key to anthropoid evolution," Gebo said. "We can see evolution occurring at this site, from the broader finger or toe tips to more narrow."