An anatomical study of an obscure sea creature called a sea spider resolves a decades-long zoological debate, according to research in this week's Nature from Amy Maxmen and colleagues.
The bodies of arthropods (jointed-limbed creatures including insects, spiders and crustaceans) are divided into segments, each of which bears a pair of limbs and the appropriate neural wiring needed to service them.
So much is clear from the bodies - the heads, however, are more complicated, as the original segmental relationships have been obscured by hundreds of millions of years of evolution. Much debate concerns the frontmost segment, which is limbless in modern arthropods.
Did this segment once bear limbs? Work on a group of ancient and bizarre fossil arthropods suggests that the first segment often bore appendages, sometimes huge and spectacular claws, but evidence from modern arthropods has been unclear.
(pp1144-1148; N&V)
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