The Centre for Fortean Zoology was founded in the UK in 1992 - nearly 20 years ago. Over the past two decades it has expanded to become a truly global organisation. We opened our American office in 2001, our Australian office in 2009, and now - in our 19th year - we are proud to welcome CFZ Canada to the CFZ global family.

Sunday 18 September 2011

Prairie Sea Monsters

Once upon a time, the large amount of land that includes Saskatchewan, Manitoba, and parts of Ontario, North Dakota and Minnesota was home to a massive sea. In the sea lived monsters with heads like horses and bodies as long as twelve meters. These monsters moved slowly but could manoeuvre through small spaces and surprise the fish that would become dinner. Sound like a fairy tale? It’s all true.

During the Pleistocene Epoch (1,600,000 to 10,000 years ago) during the last two phases of the Wisconsin Glacial Age, when the Laurentide Ice Sheet blocked the drainage of the northern Great Plains into what is today Hudson Bay, most of the area outlined above was under water; under the great sea called Lake Aggazi. In this huge lake were Plesiosaurs and other large prehistoric marine animals. Eventually, this massive sea drained east through Lake Superior, north through Hudson’s Bay and south through the Red and Minnesota Rivers. What was left, besides fertile farmland, is still being discovered.

Several important lakes are remnants of Lake Aggazi. Lake Winnipeg, Lake Manitoba, Lake of the Woods, and dozens of smaller lakes remain and the plains and river systems are all borne of this huge lake. Toward the end of the glacial era, the lake drained very rapidly, perhaps even in a period as short as a year. There is evidence of human cultures in the area as well, and many of their oral histories are still passed down through local aboriginals.

Most of these ancient lakes have something in common besides origin. All of the remaining lakes of any significant size and depth have associated reports of lake monsters dating back to these early native histories and still coming in every modern year. Many of the names of the lakes are based on the creatures seen in the lake. Turtle Lake (Saskatchewan) is so named for the “Giant Turtle” believed to live there. If such a creature exists, it would likely be a plesiosaur, as fossils of the large beast are found in the area. The food supply in these lakes remains much the same—34 of Manitoba’s 86 known fish species were evident in Lake Aggazi. If these reported sightings are actually plesiosaurs, the logic supports that theory. The lakes are big enough, deep enough, and stocked well enough to support the animals that were there ten thousand years ago.

Manipogo, Winnipogo, Woodsie, and the “monsters” of Turtle Lake, Big Trout Lake, Reindeer Lake, Dore Lake and dozens of others in the Canadian prairies are still regularly reported. Even at the relatively small Turtle Lake northwest of Saskatoon, there is at least one sighting every year and hundreds of years of native lore about the creature that will eat people in the lake. Could these hundreds of witnesses be imagining these things? It’s not likely, at least not all of them. Could it be a large sturgeon? Perhaps, but sturgeon, although they can grow to 5 meters in some cases and appear thin and scale-less, lack the ability to move in the way the reported mystery monsters move. Allopleurons and other Giant Sea Turtles were also in Agazzi, but none are thought to remain in the area.

Could the Canadian Prairie Lake Monsters be plesiosaurs or their modern cousins? It seems to be a logical answer, or at least as logical as the theory of giant sturgeon.

Further reading:,2933,341389,00.html


  1. I am happy to see your article support the notion of recent inland Plesiosaurs but I'm afraid I have to rain on our parade a mite: Lake Agassiz only existed during the deglaciation phase at the end of the last Ice age and not more than 12000 to 8000 BC; its position was also continuously shifting geographically over its existance. It really is a fascinating body of water and when it emptied out all in one go, the mass of water added to the sea was supposed to be enough to bring up the sea level the whole world over and to alter the world's climate. At the time other periglacial-meltwater lakes were emptying out besides, so it is hard to tell how much came from any one lake.

    If you DO have any references to Plesiosaur fossils actually found IN Lake Agassiz deposits, that would be a most rare and wonderful thing-but I am afraid instead that one or more of your sources has their geological strata confused.

    Best Wishes, Dale D.

  2. Thanks Dale! Is your contention that the age is incorrect or the geography? If we believe that there are current examples of plesiosaurs then the age arguement must be nil, so Im assuming that your issue is with the geography. Lake Agassiz covered over 4 million square miles during its lifetime, although not all at once. Agasszi existed in the Pleistocene era, which is relatively recent as fossils go, but there are living species from a much earlier epoch as well. The Colecanth, for instance, is a surviving relative from the Carboniferous (360-286 million years ago)epoch, so would it really be implausable for a plesiosaur to exist?

    As there are plesiosaur fossils recovered from Kansas and Montana, this certainly places the species in northern North America very near the area of the lake. In fact, depending on what you believe were the boundaries of the lake, plesiosaur fossils found in the Pembina Valley should qualify.