Somewhere in equatorial Africa, a tailed primate no bigger than a small cat creeps slowly through the treetops at night, searching for insects, fruits and edible leaves.
Jeffrey Schwartz has never seen this animal alive. But his study of its skeleton tells him that those who have seen it haven't known what they were looking at. This, says the University of Pittsburgh anthropologist, is a new species of primate.What's more, it differs so markedly from other primates that it represents a new genus, or group of species, Schwartz announced Tuesday in the Anthropological Papers of the American Museum of Natural History.
"It's almost unheard of in this century for a whole new genus to be described," said Ian Tattersall, chairman of anthropology at the American Museum of Natural History in New York City. Examples of genera (the plural of genus) among primates include Gorilla, to which all gorillas belong, and Homo, which includes modern humans - Homo sapiens - and all of humans' extinct ancestors, such as Homo erectus.
That the newly discovered animal is a primate, and thus closely related to humans, only adds to the excitement about the discovery, Tattersall added.
The animal was long mistaken for another tree-dwelling prosimian, or lower primate, called the potto. Thus, Schwartz has named the new genus Pseudopotto and the species Pseudopotto martini, in honor of Robert D. Martin, a distinguished primatologist and director of the Anthropological Institute and Museum at the University of Zurich-Irchel in Switzerland.
The bones are clearly distinct from the potto and other primates, Tattersall said. Though anthropologists are by nature cautious about adding new classifications, "I think there is ultimately very little doubt that this is a new genus," he maintained.
Perhaps as remarkable as the discovery was the manner in which Schwartz made the discovery. It was in the collections of a Zurich museum, not the forest canopy of Cameroon, that he found two Pseudopotto skeletons, misidentified for years as pottos.
"The uniqueness of this animal somehow went unnoticed," Schwartz said, though he's at a loss to explain how.
The story begins in 1987, when Schwartz was invited by Martin, his former professor at the University of London, to give a lecture at the Anthropological Institute in Zurich. As an added inducement, Martin had invited Schwartz to use the institute's famed collection of primate specimens for his research.
Schwartz was pursuing a pet theory that pottos actually represented several species. And so he pored over several dozen potto skeletons in the Zurich collection - including two that somehow seemed misplaced.
"Anybody who knows anything about pottos knows they don't have tails," he explained. One of the specimens - a virtually complete skeleton - had a tail several inches long.
And there were other differences. The teeth of the potto, for instance, include big, puffy molars and round premolars. Both Pseudopotto specimens had smaller, narrower molars and long, narrow premolars.
On the back of the neck, pottos have long spines; when attacked, the pottos curl into balls and the spines stick up, giving attackers who bite a painful mouthful. The Pseudopotto has normal-size spines on its neck, Schwartz said.
Both Pseudopotto specimens - one of which is known to have come from Cameroon - have skulls about 2 inches long. But pottos in that region tend to be bigger, with skulls about 3 inches long.
And the upper arms of the Pseudopotto are smaller and more curved than those of the potto and have a bony canal at their base that is missing in the potto.
These are major variations, Schwartz said. "It's not like splitting hairs." And Pseudopotto martini shows no greater resemblance to any other primate. Bushbabies, for instance, have smaller bodies, longer tails and a differently shaped skull.
Schwartz said it was astonishing the animal went unrecognized for so long. Little is known about where the animal that yielded the nearly complete skeleton was captured, other than "equatorial Africa," he said. Yet the animal lived in the Zurich Zoo before being donated to the museum. How could anyone have failed to notice the tail while skinning and cleaning the carcass?
The second specimen, consisting only of a skull, jaw and teeth, was captured in Cameroon in the 1960s by a Spanish primatologist. This specimen, Schwartz noted, has slight differences in the teeth from the first specimen. Once additional specimens are found, it might turn out that the second specimen actually represents a separate species of Pseudopotto, he suggested.
Though it is difficult to understand how taxonomists could have categorized the animal as a potto, it's easy to see how the animal could keep such a low profile in the wild. "We don't know much about these nocturnal primates," Tattersall admitted. Because they are active at night and live in trees, most humans have a hard time observing them.
"When you see a shape go by in the dark, you tend to fit it into a known category of animal," Tattersall continued. So, although primatologists may see Pseudopottos, they are likely to misidentify them as small pottos or large bushbabies.
It doesn't help that these animals move slowly. "They hardly even rustle the leaves as they move through them," Schwartz said.
The discovery by Schwartz doesn't necessarily change or challenge any ideas about evolution, but it adds to the diversity of primates. Though there are perhaps 20 million or more species of animals on the planet, less than 2 million have been described.
Schwartz's report "certainly will spur people to go out and find out more about his creature," Tattersall said.
As for himself, Schwartz wryly noted that he was more than willing to leave such adventuring to "more energetic, less fearful" colleagues.