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Extinct ‘mega claw’ creature had spider-like brain 520 million years ago

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Posted October 17, 2013
Research led by University of Arizona Regents’ Professor Nick Strausfeld and London Natural History Museum’s Greg Edgecombe has revealed that the ancestors of chelicerates (spiders, scorpions and their kin) branched off from the family tree of other arthropods – including insects, crustaceans and millipedes – more than half a billion years ago.

 
Extinct 'mega claw' creature had spider-like brain
This is a close-up of the head region of the Alalcomenaeus fossil specimen with the superimposed colors of a microscopy technique revealing the distribution of chemical elements in the fossil. Copper shows up as blue, iron as magenta and the CT scans as green. The coincidence of iron and CT denote nervous system. The creature boasted two pairs of eyes (ball-shaped structures at the top). Credit: N. Strausfeld/University of Arizona
 

The team discovered the earliest known complete nervous system exquisitely preserved in the fossilized remains of a never-before described creature that crawled or swam in the ocean 520 million years ago.

Described in the current issue of the journal Nature, the find belongs to an extinct group of marine arthropods known as megacheirans (Greek for “large claws”) and solves the long-standing mystery of where this group fits in the tree of life.

“We now know that the megacheirans had central nervous systems very similar to today’s horseshoe crabs and scorpions,” said the senior author of the study, Nicholas Strausfeld, a Regents’ Professor in the University of Arizona’s department of neuroscience. “This means the ancestors of spiders and their kin lived side by side with the ancestors of crustaceans in the Lower Cambrian.”

The scientists identified the 3-centimeter-long creature (a little over an inch) unearthed from the famous Chengjiang formation near Kunming in southwest China, as a representative of the extinct genus Alalcomenaeus. Animals in this group 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, which gave them their collective name, megacheirans.

Read more at: Phys.org

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