>This indicates that elaborate cytoskeletal structures arose in archaea even before the first eukaryotes appeared

Not really. It's also possible that Archaea could have continued to evolve over the last 2 billion years (as they undoubtedly have) and gained these features independently of Eukaryotes in a case of convergent evolution. Of course it's interesting either way since this group of Archaea was already thought to be among our closest relatives in the Archaea/Bacterial. It may be possible to sort this out with with genetics (are our cytoskeletal proteins evolved from theirs?).

They should have said something like "suggests" instead of "indicates" and "might have arose" instead of "arose" unless there is more to this work than is reported here.