I have described the Sundance as a “Sea of Squid.” With so many belemnites swimming around it should be no surprise that there were larger predators around to take advantage of all that calamari. Nowadays those numbers of cephalopods would be exploited by seals, dolphins and whales but 160 million years ago none of those creatures had been invented yet. Instead, the top predators of the Sundance Sea were reptiles.
Perhaps the most recognizable of all Jurassic marine reptiles were the plesiosaurs. A plesiosaur had four flippers, a long neck and a small head. Some people think the Loch Ness monster is a plesiosaur. I am not one of those people.
The plesiosaur found in the Sundance is a little beast called Tatenectes laramiensis – the genus name honors the Tate family who founded the geology museum here in Casper and the species name recognizes the town of Laramie, Wyoming – “Nectes” means “diver.” Some plesiosaurs, like the ridiculously long-necked Elasmosaurus from the Niobrara Chalk in Kansas were up to 14 meters long – the length of a grey whale. Tatenectes was a much more modest beast, only 2 meters long on the average. It could fit in your bathtub! I wouldn’t recommend taking a bath while it’s in there, though – it had very sharp teeth.
Another reptile found in the Sundance is the ichthyosaur Baptanodon. Some paleontologists think our ichthyosaur actually belongs in the European genus Ophthalmosaurus but they’re wrong. Ichthyosaurs were reptiles shaped almost exactly like a shark or a swordfish, hence the name, which means “fish-lizard.” Most ichthyosaurs averaged a couple of meters in length but some really big vertebra found near Alcova Lake are suggesting an animal the size of a pilot whale.
But the top predator of the Sundance overshadowed all of the others – the mysterious Sundance pliosaur. Unlike an elasmosaur, a pliosaur had a big head and a short neck. One species, Liopleurodon ferox from the Lias of England, had teeth just as big as those of Tyrannosaurus rex.
In 1895, Wyoming paleontologist Wilbur Knight found a pliosaur flipper in the Gas Hills of Fremont County. And what a flipper! It was 2½ meters long, making it the biggest pliosaur flipper ever found in North America. Sadly, Knight never found the skeleton of this monster and neither did anyone else – to this day it’s just known from the single flipper and a few other fragments. Knight named his find Megalneusaurus rex, which means “big swimming lizard king.” If it was built to the same proportions as the other pliosaurs, Megalneusaurus would have massed around 10 tons in life – almost twice the weight of a Tyrannosaurus! In most pliosaurs the head is about the same length as the flipper, so if the skull of Megalneusaurus is ever found it’ll be over 8 feet long – bigger than a T. rex skull with jaws broad enough to swallow an adult human like a raw oyster.
If you ever invent time travel and go back to visit the Jurassic Period, do yourself a favor: Don’t go in the ocean.
Coming up at the Tate: The Spring Lecture Series continues. Next up, at 7 p.m. on April 17 Dr. Doug Owsley, division head of physical anthropology at the Smithsonian Museum of Natural History, will talk about forensic archeology and its uses on both ancient bodies such as the Kennewick Man, and its uses in more modern events including the Waco tragedy and American Airlines flight 77. The presentation is free and open to the public and will take place in Durham Auditorium, located in Aley Hall on the Casper College campus.