''Collected from the famous Chengjiang formation near Kunming in southwest China, the four-eyed, 3-cm-long Alalcomenaeus belongs to an extinct group of marine arthropods known as megacheirans (large claws in Greek).
These animals had an elongated, segmented body equipped with about a
dozen pairs of body appendages enabling the animal to swim or crawl or
both. All featured a pair of long, scissor-like appendages attached to
the head, most likely for grasping or sensory purposes.
Alalcomenaeus solves the long-standing mystery of where this
group fits in the tree of life. It suggests that the ancestors of
spiders, scorpions and their kin (chelicerates)
branched off from the family tree of other arthropods – including
insects, crustaceans and millipedes – more than half a billion years
ago..''
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