Here is a picture of an Eophrynus prestvicii arachnid fossil cast at the Museo di Paleontologia at Sapienza University of Rome Italy. Creatures like this existed in the Carboniferous Period. Fossil was found in Great Britain.
The animal was in the order Trigonotarbida of an extinct species of arachnid. It was named by Henry Woodward in 1871 while the genus was named by William Buckland in 1837.
Source:
http://en.wikipedia.org/wiki/Eophrynus_prestvicii