A variety of explanations have been postulated over the years to account for sightings of the Loch Ness Monster. These may be categorized as: misidentifications of common animals; misidentifications of inanimate objects or effects; reinterpretations of traditional Scottish folklore; hoaxes; and exotic species of large animals.
-The Plesiosaur Theory-
Many versions of water monsters resemble dinosaurs, such as the plesiosaur dinosaur. Most scientists believe that these marine reptiles have been extinct with the dinosaurs for 60-70 million years, but others think it possible that after the last Ice Age some of these dinosaurs may have been stranded to the Loch that was connected to the sea.
Plesiosaurs were a group of long-necked, predatory marine reptiles with four paddle-like limbs. They belonged to a family known as Elasmosaurus, or thin-plated lizard which included dozen of species, the largest perhaps fifty feet long. The animal, which had a neck equal in length to the rest of its body and a tiny 30 centimetre (foot) long head, is believed to have had a finned tail which helped it swim the ocean waters using four flippers the size of paddles.
The fossilised remains of a creature with a striking resemblance to the legendary Loch Ness monster has been discovered in northern Australia by palaentologists.
Unlike Nessie, whose existence has never been proved, the five meter (16 feet) long, 700-kilogram (96 stone) plesiosaur found by fishermen west of Cairns in northern Queensland was no joke. It lived in the early Cretaceous period 112 million years ago on a diet of fish and squid.
Others, like David Hall, feel that lake monsters could not possibly be plesiosaurs since plesiosaurs were cold-blooded reptiles that would have preferred warm oceanic currents to cold Scottish Lochs.
Paleontologist Robert Bakker has recently argued that plesiosaurs did not, as once believed, sail unaffected through the extinctions, which punctuated the Age of Reptiles. Instead, the true plesiosaurs died out at the end of the Jurassic period, and similar reptiles quickly evolved to take their ecological niche. If there is a chance that dinosaurs have survived the K-T extinction at the end of the Mesozoic era and lived on to the present day, there are not plesiosaurs but descendants or hybrids.
Another theory supports a snake-like primitive whale known as Zeuglodon.
"Plesiosaurs are widely referred to as "aquatic dinosaurs," though they were actually a type of reptile that lived in the oceans during the Mesozoic Era and supposedly died at the close of the Cretaceous Period along with the dinosaurs. But recent research from paleontologist Robert Bakker has shown that plesiosaurs did not, as once believed, live through the extinctions that punctuated the Age of Reptiles. Instead, the true plesiosaurs died out at the end of the Jurassic Period, not at the end of the Cretaceous, and similiar reptiles quickly evolved to take over their ecological niche. A reptilian Waterhorse, therefore, would be a distant relative, at best, of the well-known plesiosaurs.”
note: The term “water horse” (also spelled as “Water Horse” and “Waterhorse”) was originally a name given to the kelpie, a horse like creature similar to the hippocamp that has the head, neck and mane of a normal horse, legs like a horse, webbed feet, and a long, two-lobed, whale-like tail. However, the Water Horse term has also been used as a nickname for lake monsters, particularly Ogopogo and Nessie.
"The best evidence suggestive of the existence of plesiosaurs in a lake comes from the 1972 images captured by an underwater camera in Urquhart Bay in Loch Ness. In August of that year, Robert Rines and his team from the Academy of Applied Science in Boston caught a 20- to 30-foot-long something both on sonar and on camera (see case, pages 111-114). Two computer-enhanced images show a four- to six-foot-long diamond-shaped object with a median keel and a pointed tip attached to a larger body. This object looks very much like a rear flipper, but not the flipper of a seal, a whale, or any other aquatic mammal, nor the fin of an eel or a ray-finned fish. What it looks like is the rhomboidal-shaped flipper of a prehistoric plesiosaur. Though it could be what a flipper of an evolved pinniped would like like, too.
While in outward appearance the Waterhorse certainly looks like a plesiosaur, is it actually a plesiosaur? One obstacle to the Waterhorse-as-plesiosaur theory is the lack of verified plesiosaur fossils after the Cretaceous - a ghost lineage would have to exist. The other major obstacle is that the plesiosaur was a marine species. How could freshwater Waterhorses be plesiosaurs then?
Biologist Roy Mackal points out that some plesiosaur fossils have indeed been found in rivers and estuaries - conditions that imply a freshwater environment. Mackal speculates that while pursuing fish or escaping marine predators, plesiosaurs may have traveled up rivers and into lakes, thus echoing the Victorian notion of the “land-locked Sea Serpent,” of course. With ample food and a lack of predators, plesiosaurs may have gradually been transformed into freshwater species.”
Unlikely? It has happened before. There exist 43 species of elasmobranch - sharks and rays - in ten genera and four families, which have penetrated freshwater environments in Australia, Southeast Asia, western Africa, eastern South America, Central America, and southeastern parts of North America. This marine-to-freshwater transition is also represented among mammals. The seals of Lake Baikal in Siberia and five species of freshwater dolpjoms worldwide (Ganges River Dolphin, Indus River Dolphin, Amazon River Dolphin, Yangtze River Dolphin, La Plata Dolphin) serve as examples. Common seals have been recovered from Loch Ness and Lake Champlain, so ocean-to-freshwater movement still occurs today.
The third major obstacle to the plesiosaur theory involves features reported by eyewitnesses but not exhibited by fossil plesiosaurs on record. These include hair, horns, dorsal humps, and the absence of a tail. Zoologist Karl Shuker, perhaps the strongest advocate for a plesiosaur explanation, argues that there are “perfectly reasonable explanations for the morphological differences between such creatures and fossil plesiosaurs.” The “hair” and “whiskers” reportedly seen on Waterhorses, he suggests, may be soft-tissue sensory filaments that would leave no fossil traces, while the “horns” or “snorkels” could be breathing tubes. And the dorsal humps may not be undulations of the animals’ bodies but either a fatty tissue, inflatable air sacs, or exposed portions of a dorsal crest.
Despite holdouts to the notion that Waterhorses like the Loch Ness Monster are plesiosaurs, the general consensus today is that the whiskers, the mane, the hair, the wide mouth, the up-and-down swimming movements, and the cold-climate range all point to this animal being a mammal. The two mammal candidates most often discussed are the zeuglodon and the long-necked pinniped.
Zeuglodon is the most commonly used name for a group of long, serpent-like fossil whales. Much of the attention has been on Basilosaurus, an extinct genus of primitive whales of the family Basilosauridae (suborder Archaeoceti) found in Middle and Late Eocene deposits in North America and northern Africa (the Eocene Epoch lasted from 57.8 to 36.6 million years ago). Basilosaurus had a primitive dentition and skull architecture, and ranged from 55 to 75 feet long, with a skull 5 feet in length. The zeuglodon is the favorite candidate of several researchers, including Roy Mackal, Champ researcher Joseph Zarzynski, and Sea Serpent chronicler GaryMangiacopra, who theorize, that the animal may be responsible for some modern reports of Lake Monsters and Sea Serpents. Mackal believes that the zeuglodon is the best fit for the reports of Lake Monsters in British Columbia's Lake Okanagan, Scotland's Loch Ness, and Vermont and New York's Lake Champlain.”