This week we’ve introduced the kids to Walking with Dinosaurs, which takes you to a place and time were reptiles were huge and CGI budgets were relatively small. We were two episodes into the the six-part series when the five year-old noted that there only seems to be a handful of different species of dinosaurs around in any given epoch. Generally, each episode features a meat eater, a plant eater, a very big meat eater and a turtle.

The reasons for this are obvious, chief among those are budgetary. CGI still costs money today, and these things were made in the late 90s. Beside, why spend the money on background dinosaurs? It would only confuse viewers anyway. It does, however, deprive viewers of the notion. Still, this isn’t a post to review a decade-old documentary, no matter how watchable it remains. (If updated, I’m sure it would simply feature more feathers, which seems to be the way our notions of dinosaurs are evolving.)

Besides, the kids love Dinosaur Train and we felt it was time to show them the truth about dinosaurs, that Laura the Giganotosaurus wouldn’t necessarily get along with little Ned the Brachiosaurus…and not just because they come from different ends of the Cretaceous.

Last night we watched the Cruel Sea episode, featuring gigantic liopleurodons — the big nasties of their day — and plesiousaur-like cryptoclidus. Certainly, the Jurassic seas would be teeming with more than just five or six species of beast. Most of which, I’m sure would kill you if you were there, much like I perceive anything off the coast of Australia, from salt water crocs (who would be at home in the Cretaceous) to great white sharks (ditto) to teeny cute little octopuses that will kill you if you accidentally step on them.

The truth is that it took a vast ecosystem to support apex predators like liopleurodons and smaller fish-eaters like cryptoclidus. That’s why I am always fascinated with people who claim that the various lake and river monsters around the world are plesiosaurs. And they never see small plesiousaurs either, like cryptoclidus, which measured in at about three meters. But even at three meters, a herd or pod or whatever the hell you call a group of these things would require a lot of fish to eat. And there would have to be more than one. Even if this particular lake monster was the last of its long-lived kind, one would think you’d find fossil evidence of recent critters of its kind around.

Take this story for example, the Hawkesbury River beastie. Now, color me a judgmental skeptic (which would be chartreuse, perhaps?), but I’m going to go off the bat with doubts that they have a dinosaur in their river.

Descriptions of the Hawkesbury River Monster liken it to the prehistoric plesiosaur, an aquatic dinosaur 70 million years extinct.

The Loch Ness monster is also said to be related to the same extinct creature. How the Nessie myth is similar to our own, HERE

Mr Jones said plesiosaurs did exist in Australia, but ther was no evidence of them inhabiting the Hawkesbury River.

However both Mr Gilroy and Mr Jones describe the aquatic dinosaur as grey and mottled in colour, with a large bulky body, two sets of paddle-like flippers, a long neck and serpent-like head and thick, eel-like tail.

Sighting reports describe it as about 24m long. Mr Jones said the plesiosaur grew up to 10m long.

Mr Gilroy said he and his field assistant Greg Foster may have sighted the creature last August, from a high bank near Wiseman’s Ferry.

They described seeing a dark, bulky shape with a long neck about a metre from the surface.

Its movements caused surface disturbance which appeared to suggest a marine creature with two sets of flippers and a tail, Mr Gilroy said.

The Mr. Jones quoted here Robert Jones, a paleontologist from the Australia Museum, and if you notice here that the reporter suggests that Jones and the cryptophile Gilroy are describing similar creatures, although at no point does he mention Gilroy seeing anything more than a long-neck. All of this sounds familiar. In fact, it sounds like Nessie and Champie, both lake creatures purported to be plesiosaurs and also purported to be among the legendary creatures of the local natives. I’m just going to through this out there and say that, perhaps, they are not seeing similar creatures but, instead, they are seeing similar phenomena, whether it is an animal or just a convincing mixture of logs and currents.

Ben Radford, editor of Skeptical Inquirer, wrote a great book with Joe Nickell about lake monsters, called Lake Monster Mysteries, in fact. In it, they investigate a number of the world’s great lake monsters and generally find sincere, thoughtful people, like Gilroy, who are absolutely convinced that they see a plesiosaur.

From their conclusion:

Although many sane and sincere people think they are seeing lake leviathans, in all likelihood they are encountering something they misperceive as such. We have given many examples in this book, including otters, eels, logs, and beavers. These eyewitnesses are not foolish; they are subject to the same psychological and perceptive errors that plague all of us from time to time.

I don’t doubt that these people think that they’re seeing something in Hawkesbury river. They’re not crazy, although their conclusions are more than a little premature. And I don’t doubt that Aborigines, Native Americans and ancient Celts all saw something similar in Hawkesbury, Lake Champlain and Loch Ness, respectively. (Of course, they interpreted these things as dragons and serpents and whatever a moolyewonk is, since they didn’t know about plesiosaurs.) Something like a 24 meter plesiosaur, however, would be awfully tough to hide. They’re air breathers, they need to eat a lot of fish, and they laid eggs on land.

Having one of these in your lake or river, no matter how well it hides, would have some affect on the local environment. It would be like having JD Salinger in your neighborhood. He may not be available for interviews and photographs, but the neighbors have seen him and he still gets mail delivery.