Rare primate's fossil closer to lemurs than humans

Based on how its teeth erupted, a model has suggested that a rare fossil of an early primate shares more in common with modern lemurs and not with monkeys or humans.

Their model also suggests that Darwinius -- the best preserved fossil primate known to exist -- was a little older at the time of death and would have weighed slightly less as an adult than the original estimates predicted.

The model, developed by Sergi Lopez-Torres and associate professors Mary Silcox and Michael Schillaci from University of Toronto, re-examined the interpretation of Darwinius.

By looking at the sequence in which adult teeth come 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," said Lopez-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, Lopez-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, the ancestor to monkeys, apes and tarsiers, and the ancestor to all primates - share the same dental eruption sequence with each other.

That pattern shares some similarities with the dental eruption sequence found in Darwinius.

The team that originally discovered Darwinius argued the 47-million-year-old fossil was more closely related to haplorrhines, the group that includes anthropoids (monkeys, apes and humans) and tarsiers.

Subsequent studies by the same group suggested Darwinius was specifically related to anthropoids, the primate lineage in which humans belong.

"Our goal as palaeontologists is to bring these animals back to life. It's the best preserved fossil primate. It even has stomach contents, so there's a lot of potential for understanding its biology," Silcox said.

The model is explained in a paper published in the journal Royal Society Open Science.