STL Science Center

STL Science Center

16 February 2013

Tylosaurus Swims Again

Older images of Tylosaurus, as I said yesterday, are quite fantastic. This image, from the turn of the 20th Century, is fairly typical of older drawings. The dragon-like appearance of older Tylosaurus drawings is not usually exactly like this in one very special aspect: the hairy appearance of the dorsal ridge. The backs of Tylosaurus were originally drawn with large flowing "manes" of thin skin that undulated while the body moved, snake-like, through the water, propelling itself through the water with its tail. In that aspect of motion ideas have not changed very much over the years; the tail is still proposed to be the main propelling force for mosasaurs such as Tylosaurus with the fins acting as stabilizers more than as paddles. Snake-like motion is probably a bit of an exaggeration, though related to snakes, as only the tail would have been really needed for propelling Tylosaurs through the water. The most un-reptilian mane of hair has not actually been documented on Tylosaurus (nor has there been any feathering) so the mane can be interpreted as purely an artistic interpretation.

Fast forward a few years to Charles Knight's interpretation of Tylosaurus and we see the exact same ecological positioning of Tylosaurs; it is chasing down some rather large and tasty looking morsels in the Late Cretaceous seas. This turbulent ocean landscape is a little bit more evolved, so to speak, in terms of Tylosaurus. This Tylosaurus has no exaggerated dorsal ridges, though the spinal ridge is still highly visible. Another strange bit of this illustration is that the Tylosaurus has chased the fish it is attempting to eat directly out of the ocean and is continuing to pursue them above the waves. Tylosaurus most likely would not have been too excited about chasing its food out of the water. It was most likely not an extremely fast or agile swimmer; it more thank likely surprised its prey from below.

That makes this image even more shocking and unrealistic. While the accuracy of an attack from below is probably better than a Tylosaurus attempting to chase down fast moving fish- the fish above are smaller faster movers than the large predatory fish of the ancient sea, such as the Squalicorax shark that this Tylosaurus has surprised and tossed out of the water- the attack from below makes much more sense in terms of how a Tylosaurus actually would have hunted its prey with the highest success rate. The unlikely part of this image is that the Tylosaurus is nearly halfway (which would be about 27feet of reptile) out of the water, which would require an amazing amount of energy and quite a bit of speed; a highly inefficient method of stalking and killing prey when the predator in question has a less than perfect kill per hunt record. In reality a shark like this would more than likely have been bitten completely in half by the large powerful jaws of this Tylosaurus.

I do not even have anything to say to this illustration really. I think it is attacking a plesiosaur, but it looks like some sort of weirdly exaggerated duck. Also, its tail is extremely hyperbolic in terms of being shown as a paddle. Seriously, just soak this one in. Supposedly it was a print that was sold in Germany in the late 19th Century.

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