Plesiosaurus, the "Near Lizard," was a small aquatic reptile at less than four meters long. The first complete fossil was found by the first female paleontologist, Mary Anning. Its family Plesiosauridae is  characterized by having a small head mounted on a long neck and four fins on a body with a stubby little tail. Sound familiar? Because the Loch  Ness Monster is said to have similar features, it is commonly believed to be a Plesiosaurus. However, although Plesiosaurus lived in the  prehistoric UK, it died out in the  Jurassic Period, which means there  is no chance that any could have  survived in the Loch for over a  hundred million years.   Plesiosaurus lived in open ocean, using is four paddle-like fins to propel itself in chase of fish and cephalopod prey. It may not have  been able to smell underwater, so it would have had to rely on other senses to find food. Contrary to popular belief, Plesiosaurus and its relatives did not crawl on land to  lay eggs, so they won't be building sandcastles anytime soon. Instead,  it remained in the water to give  birth to live young. Paleontologists learned this from a remarkable  fossil of the plesiosaur  Polycotylus, which displays the  bones of an adult and its single  developing infant.