Darwinius' Teeth Suggest More Closely Related to Lemurs Than Monkeys

A famous fossil of an early primate shares more in common with modern lemurs based on how its teeth erupted, according to new model developed at U of T Scarborough.

The model, developed by PhD student Sergi López-Torres and Associate Professors Mary Silcox and Michael Schillaci, re-examined the interpretation of Darwinius, the best preserved fossil primate known to exist.

By looking at the sequence in which adult teeth come in - known as dental eruption - in primates, they found it had more in common with lemurs than squirrel monkeys, the model species used by the researchers who discovered Darwinius.

"Every species has a particular pattern by which their teeth come in and this allows us to estimate the age of fossils that died before their adult teeth could emerge," says López-Torres. "It seems that the pattern of dental eruption for Darwinius is more similar to that of lemurs than to that of monkeys."

Before looking at Darwinius, López-Torres did a large study of 97 living and fossil primates in order to get a clearer picture of how different species compare through patterns of dental development. He found that the three most primitive ancestors - the ancestor to lemurs and lorises, the ancestor to monkeys, apes, and tarsiers, and the ancestor to all primates - share the same eruption sequence with each other. That pattern shares some similarities with the dental eruption sequence found in Darwinius.

"The major difference is we found that anthropoids (ancestors to monkeys, apes and humans) are characterized by a late eruption of the third molar, which is something Darwinius clearly doesn't show," he says. "One idea that still stands links Darwinius to anthropoids, but since it doesn't show this late eruption, it looks more like a modern lemur."

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