Fossil Friday!

Welcome back to Fossil Friday!  We had a great run in 2013: some vertebrates, lots of skulls, many formerly squishy things. To start us off for 2014, I thought I'd challenge you with this full skeleton. This fellow was an aquatic vertebrate, about the length of my hand. Who was this tiny swimmer? Where did it come from? What age did it live in?

Give us your answer in the comments section below. The first person to correctly identify this critter wins bragging rights for the year!