Living Fossils - Paddlefish
The Paddlefish is a primitive ray-finned fish, belonging to the order Acipenserifrmes, which includes sturgeons, Paddlefish, and some extinct families, they are considered to be relatively primitive fish (Read more here.) They can be distinguished by their long, spatula-shaped snouts, called rostrum, and their large, gaping mouths. While not closely related to sharks, they have similarities, such as a cartilaginous skeleton, and highly forked heteroceral tail fins.
There are two extant (possibly) species of Paddlefish, including the American Paddlefish (Spoonbill, Mississippi Paddlefish, Spoonie, Spoonbill Catfish) (pictured above,) and the Chinese Paddlefish (Chinese Swordfish,) which may be extinct, but is believed to be critically endangered. That said, there are four, maybe five extinct genera.
They feed on zooplankton by filtering water through their gaping mouths as they swim, catching said plankton in filaments in their gill arches called gill rakers, much like basking sharks. It has electroreceptors in its rostrum, which allow it to detect weak electrical fields, and a potential meal.
Picture comes from the Wikimedia Commons, it is in the public domain, as it is the work of the Fish and Wildlife Service, but can be credited to Timothy Knepp, information here: http://en.wikipedia.org/wiki/File:Paddlefish_Polyodon_spathula.jpg