PLESIOSAURS
The name plesiosaur is derived from two Greek works, "plesios" meaning "near to" and "saurus" meaning "lizard." This name refers to the fact that its skeleton is "nearer to lizards" than some of the other marine reptiles. The classic description of the plesiosaur was that it resembled "a snake threaded through the shell of a turtle." The plesiosaurs are quite unlike any animals today and they have no living descendants.

PHYSIOLOGY
Plesiosaurs were descended from land-dwelling ancestors. The limbs were modified into paddles with which the body of the animal was rowed through the water. The limbs acted as oars that could be pulled, backed, and even feathered. The neck allowed for darting movements to be made in pursuit of prey.

Like the mosasaurs, plesiosaurs were carnivorous, scaly-skinned, air-breathing, and likely viviparous, though some species appear to have been capable of dragging themselves out of the water to lay eggs on dry land. Plesiosaurs varied considerably in size and some were over 40 feet long.

PLIOSAUR
One group of plesiosaurs, the pliosaurs, had very short necks and large heads, which become relatively larger in the biggest kinds. The Australian pliosaur Kronosaurus was about 40 feet in length, of which the skull accounted for 9 feet, the largest head of any known reptile. The pliosaurs probably lived as sperm whales do today, diving to hunt larger cephalopods.

ELASMOSAUR
A second group of plesiosaurs, the elasmosaurs, had long necks and small heads. They culminated in the North American elasmosaurs, which reached a length of 40 feet, 23 feet of which was neck. Many scientists now believe that their long necks were not as flexible as portrayed by many early artists. Elasmosaurs probably held their necks rather stiffly out front and fed by coming up slowly under a school of fish and grabbing what they could.

LOCH NESS MONSTER
Since the first dramatic photograph of a supposed Loch Ness monster, taken in 1934, the evidence that there are still unidentified creatures in the loch has mounted dramatically. "Sightings" have risen into the hundreds. Sonar tracings, motion pictures, and underwater photographs have added additional evidence. It is not conclusive because the photographs, especially those taken in the thick, peaty water, are indistinct.

The evidence suggests that the creatures, of which there must be enough to form a breeding community, can swim up to 10mph and grow up to 25 feet long. They live mainly in the depths, but can also venture onto land. They have small heads, bulbous bodies, and tails.

It is theoretically possible for a community of animals to live in Loch Ness. They would have space enough; the loch is 900 feet deep in places. The loch's immense quantities of salmon would make an ideal food supply. But what type of creature could "Nessie" be?

One theory is that the monster is a plesiosaur. Plesiosaurs were roughly the right shape, could swim fast, and fed on fish. The underwater picture of a "flipper" taken in 1972 by Robert Rines closely resembles that of a plesiosaur.

There are objections to the suggestion. Plesiosaurs were air breathing, and if there were a whole community of the creatures in Loch Ness, the surface would be broken several times an hour as the animals rose to breathe. Secondly, the temperature of the water is a fairly constant 42° too cold for any known reptile.