Big things fascinate scientists - dinosaurs, mountains, monster trucks. And, it isn't any different for arthropods - like insects and crabs. The largest arthropods ever discovered are the Eurypterids. These massive scorpion-looking things were discovered recently and are thought to have been up to 2.5m long (7 feet for you Yankee audience). 

Their size has been estimated based on footprints that are over 360 million years old, that have been preserved in sandstone in Scotland. These 'footprints' look like erosion, or pretty much anything but ancient massive lobster cousins... except to experts like Dr. Martin Whyte from the University of Sheffield. When you look close, really close, you can sound smart and say that yes - you can see it....and that it clearly is the tracings of a sea scorpion. 

You can't see it?  Huh, too bad for you.

_{Host:  Torah Kachur}

_{Photo Credits: Martin Whyte, Nature; Wikimedia Users: Nobu Tamura, sketchedout.com, freakingnews.com, ebiscuit.com}

_{References:  http://www.msnbc.msn.com/id/10266534/}

_{http://news.nationalgeographic.com/news/2007/11/071121-giant-scorpion.html}

_{http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/8632427.stm}