18 August 2014

"Legs modified for chewing"

It's called Hallucigenia because researchers have scratched their heads over where it fits among life forms since its fossil was discovered in the Burgess Shale of Canada's Rocky Mountains in the early 1970s...

A new study of the claws at the end of all those legs revealed... an oddity observed in at least one other place, the weird jaws of velvet worms, which, in the university's synopsis of the report, "are no more than legs modified for chewing."..

The finding is a big deal, said Javier Ortega-Hernandez, a co-author of the study, because it turns what is known about the evolutionary tree of arthropods -- spiders, crustaceans and insects -- on its head. "Most gene-based studies suggest that arthropods and velvet worms are closely related," Ortega-Hernandez said. But "our results indicate that arthropods are actually closer to water bears," he said.
More at the Washington Post.  The full manuscript was published in Nature.


  1. To be fair, all arthropod jaws are also "legs modified for chewing" (I don't know about tardigrades mouthparts, though I would assume the same is true for them given no other information). Limbs, antennae, gills, and mouthparts are all appendages analogous to one another, just on different segments (the head has quite a few segments smushed together so as to be unrecognizable after early developmental stages).
    This is a very cool paper, though. They have really good support for the Tardigrade+Arthropod hypothesis on their cladogram. Original paper here: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13576.html

    1. Thanks for the Nature link, which I've added to the post.


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