In this short article
on the New Scientist website, Chris Beard, one of the prominent critics of the Ida paper, sets out his objections to the taxonomic classification given to the fossil.
Originally Posted by Chris Beard, New Scientist
What does Ida's anatomy tell us about her place on the family tree of humans and other primates? The fact that she retains primitive features that commonly occurred among all early primates, such as simple incisors rather than a full-fledged toothcomb, indicates that Ida belongs somewhere closer to the base of the tree than living lemurs do.
But this does not necessarily make Ida a close relative of anthropoids – the group of primates that includes monkeys, apes – and humans. In order to establish that connection, Ida would have to have anthropoid-like features that evolved after anthropoids split away from lemurs and other early primates. Here, alas, Ida fails miserably.
He doesn't explain why he thinks the PLoS paper's interpretation 'fails miserably' though, so I guess we'll have to wait for his reasons why.
He does give a nice graphic showing what the controversy is about. It shows two alternative placings of the Ida fossil in the evolutionary tree. The upper one, in pale pink, is the one advocated in the PLoS paper. The lower one, in red, is the one he favours.
NB - if the PLoS paper authors are right, Ida might still not be a direct ancestor of ours, and could be an off-shoot from our lineage, as in this version I've hacked:
There's also a problem with official recognition of the fossil Latin name, as proper procedure wasn't followed. PLoS is hastily trying to fix things up. Story here