Remains of ancient primate found in Oregon

Scientists have unearthed fossil teeth and a jaw fragment in Oregon. And these have helped flesh out the features of an ancient animal that once lived in North America. A new species of primate, it had features similar to a modern lemur’s.

Artist’s conception of what North America’s last nonhuman primates might have
 looked like. The animals are shown on a hackberry tree. It’s the most common 
plant known from the sediment layer in which the fossils were found 
[Credit: Christopher Herndon]

Primates are a group of mammals that includes monkeys, lemurs, gorillas and humans. The Sioux are a tribe of Native Americans. The newfound primate’s genus name comes from a Sioux term for monkey: Ekgmowechashala. These last nonhuman primates to live in North America vanished around 26 million years ago. No other primates lived in North America until humans arrived well over 25 million years later. This timeline comes from the new study. It was published June 29 in the American Journal of Physical Anthropology.

Joshua Samuels works for the National Park Service in Kimberly, Ore. As a paleontologist, he studies ancient fossils. He and his colleagues dug up the ancient primate bones between 2011 and early 2015. They found two complete teeth, two partial teeth and a jaw fragment.

All came from rocky sediment at Oregon’s John Day Formation. This rock layer, or stratum, contains fossils from between 30 million and 18 million years ago. A tooth and jaw fragment from the same species had been found there previously. All the fossils belong to a new species of Ekgmowechashala, the researchers say. Partial jaws and teeth of a related species had turned up at sites in South Dakota and Nebraska.

The scientists figured out the age of the fossils based on their position between layers of volcanic ash. The ages of those layers was already known. That let the scientists determine that the new fossils must be between 28.7 million and 27.9 million years old.

Where did the primates come from?

Millions of years ago, land connected what is now Alaska and Russia. The ancient primates probably crossed that “land bridge” around 29 million years ago, the researchers now say. That journey would have taken place some 6 million years after other North American primates had died out.

Samuels says the new fossils appear to resemble those from a 34-million-year-old primate from Thailand, in Southeast Asia. The new fossils also are similar to a 32-million-year-old primate from Pakistan, which lies between the Middle East and India.

Erik Seiffert is a paleontologist at Stony Brook University in New York. He suggested an Asian–North American primate connection back in 2007. But Samuels and his team “have laid out the evidence in more detail,” Seiffert now says.

Some researchers suspect Ekgmowechashala’s closest present-day relatives would have been tarsiers. These small primates live on islands in Southeast Asia. Other scientists think the now extinct North American primates were more closely related to lemurs. They exist only in Madagascar. It’s an island off of the East Coast of southern Africa.

K. Christopher Beard agrees with Samuels’ team that Ekgmowechashala is likely more related to the lemurs. A paleontologist, Beard works at the University of Kansas in Lawrence. But he argues that to confirm this, scientists need to find ankle bones. They should point out whether the ancient primate species had a greater kinship to lemurs or to tarsiers.

Author: Bruce Bower | Source: Student Science [August 13, 2015]