This illustration shows the nervous systems of the Alalcomenaeus fossil (left), a larval horseshoe crab (middle) and a scorpion (right). Diagnostic features that reveal the evolutionary relationships ... more 
This illustration shows the nervous systems of the Alalcomenaeus fossil (left), a larval horseshoe crab (middle) and a scorpion (right). Diagnostic features that reveal the evolutionary relationships among these animals include the forward posi less 
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LiveScience.com | Photo By N. Strausfeld/University of Arizona
Wed, Oct 16, 2013 2:00 PM EDT