The ankle bone fossils reveal that Dormaalocyon lived an arboreal life, scampering through the trees in what was then a humid, subtropical forest, the researchers report. It likely looked like something of a cross between a tiny panther and a squirrel, with a long tail and a catlike snout.
The study confirms previous work suggesting that carnivores emerged during the Paleocene, before Dormaalocyon's time, said Gregg Gunnell, the director of the division of fossil primates at the Duke Lemur Center in North Carolina, who was not involved in the research.
"It really shows that there is a lot of diversity very early in the Eocene, and we have absolutely no idea where it came from," Gunnell told LiveScience.
Part of the challenge of uncovering carnivore history is that, on the whole, meat-eating mammals aren't that common, Gunnell said - there are many more herbivores and omnivores on the planet and in the fossil record. In addition, Solé said, fossils from Europe, which appears to be an important stop for, and potentially the origin of, carnivore evolution and spread, are rarer than fossils from North America.
The geographical origin of the carnivoraforms remains mysterious, however. One theory holds they originated in North America and spread to Europe; the relationships of the fossils in Dormaal seem to suggest something more complex, Solé said. It's possible that carnivoraforms began in Asia and made it to North America through Europe.
With the current fossil record, however, it's just not possible to say for sure. Solé and his colleagues will soon publish a paper on a new fossil site in France from the late Paleocene - and a new carnivorous mammal found there - that may hold answers.
"We need to find some Paleocene deposits that produce some kind of ancestors of these carnivoraforms," Gunnell said. "We're lacking a big chunk of information."
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