Your Daily Fossil

Elasmosaurus

First mounted specimen is at the American Museum of Natural History, NYC.

Reconstruction by Todd S. Marshall. 

When: Cretaceous (~80 million years ago)

Where: Widespread in Cretaceous seas

What: Elasmosaurus is a plesiosaur. It has the longest neck of any known plesiosaur, made up of over 70 cervical vertebrae.  In total it was 46 feet (~14 meters) long, with roughly half of this length made up of the neck. Elasmosaurus was named by Cope in the mid 1800s, and in this paper he made a rather famous blunder. He reconstructed the head of Elasmosaurus attached to what we now know is its tail. I say ‘now know’ but almost immediately upon publication of the specimen, the scientific community pointed out Cope’s blunder. To be as fair as possible to Cope, he was a self educated man and at the time was much more familiar with lizards, especially the giant mosasaurs, which do have spectacularly long tails. Additionally the first plesiosaurs with exceptionally long necks were just being discovered in Europe at this time. Still though, it is a good example of how you should be very careful not to let any preconceived notions you may have distort what is right in front of you. 

Despite a number of artistic reconstructions,  Elasmosaurus could not lift its body, or even most of its neck, out of the water. All it could do is breach the surface of the water with its head for air. As the animal could not survive out of the water, let along drag itself around with its highly compressed paddles, Elasmosaurus must have given birth to live young. While we have no direct evidence of vivipary in this particular plesiosaur there are amazing fossils of closely related forms showing live birth. Elasmosaurus also was not capable of coiling its neck in a ‘snake like’ manner. Its long neck was used to allow it to move its head close to schools of fish, while its body would remain far behind. It would swim beneath its prey and then lift its head up, creating far less disturbances in the water than its large body would, and allowing it to quickly snack on unsuspecting fish.