A Northern Illinois University anthropology professor has assembled the world’s largest collection of early primate fossils.
Dr. Dan Gebo’s collection of more than 500 finger and toe bones represents more than two dozen species. They belong to tiny primates from the mid-Eocene period-- about 45 million years ago.
Most of the fossils are between one and two millimeters long. That’s about the size of a mustard seed. Gebo says the primates they belonged to would have been half the size of a mouse.
Gebo says the shape of the grasping big toes and thumbs implies the primates were arboreal. But he says the life of a small primate is very different from that of a large primate.
“Their metabolic rate is very high, so they have to eat a lot of calories quickly," Gebo explained. "They’re going to have to go eat certain things like fruit and insects -- essentially what primates eat. Of course, if you’re small, you’re going to get preyed upon very heavily.”
Gebo says it was easy to determine these fossils belonged to primates, despite their small size.
"Primate fingers and toes are very distinctive because we all have nails, and most mammals have claws or hooves," Gebo said. "So they’re kind of flat-line bones with an arrowhead type shape because of the nails.
The bones in the collection were excavated from a “fossil hotbed” in Southeastern, coastal China—about 100 miles west of Shanghai.
Gebo says the site--called Shanghuang—is famous among anthropologists for its diversity.
He says it’s extremely rare to find a locality containing all three major groups of primates — one group related to living lemurs, another group related to living tarsiers, and the anthropoid group from which humans, monkeys and apes evolved.
The collection took about 20 years and the screening of 10 to 20 tons of limestone to accumulate.
"Not only do we have a large collection of these finger and toe bones, but we also have them in all the major groups of primates, some of which are the first time you ever see these groups in the fossil record," Gebo said. "So it tells us something about the initial adaptations and how they’re educationally connected.
Gebo says the diversity of his collection will allow researchers to make connections between the Eocene primates and the original fossil primates dating back 55 million years.
Gebo says there’s another unique aspect to this collection.
“As it turns out, the living lemurs have a funny second digit on their foot and it has a grooming claw,” Gebo said.
Gebo says that — up until a few years ago — it wasn’t believed that grooming claws had been found on fossil primates. But his collection contains 15 fossils with grooming claws.
The fossils are currently kept in small gelatin capsules in Gebo’s office at NIU. They eventually will make their permanent home at China’s Institute of Vertebrate Palentology and Paleoanthropology.