How rude... correcting a museum!

 


It goes without saying that natural history museums are full of experts in their fields, and that one person's area of expertise is another person's area of total ignorance. I pick up my grandson from the Denver Museum of Nature and Science (DMNS) on a regular basis, and we spend many hours roaming the halls. Over time, I've noticed some errors, inconsistencies, and puzzling displays. I recognize that, unlike something on a screen that can be altered with a few keystrokes, displays are complicated things to change. But, step one has to be noting that they actually should be changed. I'm going to go out on a limb and propose some changes. These suggestions sometimes will be in my area of expertise, and sometimes will not. I'm going to start with one that is absolutely not within my expertise, but caught my attention because of my experience. It starts off with... a plesiosaur skeleton.


Signage for this plesiosaur, Thalassomedon haningtoni, discovered in 1939 in Colorado.

Now, I probably wouldn't be able to recognize a plesiosaur if it bit me. Ancient reptiles are not my forte. But I am a diver, and the thing that caught my attention was the display of this swimming plesiosaur catching fish.




Eating fish makes sense. The teeth of Thalassomedon seem adapted for fish capture and holding, although they could also handle other soft and hard-bodied invertebrates.

Detail of a Thalassomedon skull at the American Museum of Natural History.

Detail of the Thalassomedon skull at the Denver Museum of Nature and Science.

Unlike other short-necked plesiosaurs, Thalassomedon had 50+ cervical vertebrae... a very long neck, indeed. For comparison, most mammals, from mice to giraffes, have 7.

So why does the display of Thalassomedon catching fish capture my interest? First, the general body form of active fish predators is not a long neck. Think sharks, orcas, seals, and tuna. To outswim a fish, the general body plan is sleek, fusiform, and compact.

The predatory barracuda.

Second, as a swimmer and a diver, I recognize the density of water, and the resistance experienced when moving arms and legs through it. We can't be underwater fish predators without technological help (spears, nets). To think that an animal with a long neck could push through water fast enough to catch a healthy fish just seems implausible. The animal has the body form of a sea turtle with a very, very long neck. You won't see sea turtles chasing fish. Nor divers.

Artist rendition of relative size of Thalassomedon.

Now, the display of this skeleton in the American Museum of Natural History has it either hunting or swimming with a more horizontal profile compared to the display in the DMNS.



I speculate that 
Thalassomedon wasn't an active fish predator, but rather used it's long neck to reach under ledges or in holes to grab fish, or else specialized in slow moving (non-fish) prey. In addition, that neck would have been very vulnerable to a bite from a predator, but perhaps, as with whales, size gave some immunity, as would living in shallower waters.

The correction? I wouldn't have this plesiosaur actively chasing fish. 


There is also a mural of this plesiosaur in the Science Atrium, also chasing fish.






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