Name Meaning: Hidden Clavicle (collarbone)
Location Found: England
Geologic Era: Middle Jurassic
Size: Up to 4 meters long
Estimated Range: Modern England and France (possibly South America as well)
Extinction Date: 164 million years ago
Our portion of Cryptoclidus is a vertebra with a large amount of wear on it. The processes are missing, though one can see where they would have attached. The vertebra is similar in shape and structure to the other plesiosaur vertebra in the collection (see Zarafasaura oceanis). The coloration is much different, with the Cryptoclidus vertebra coming from a clay deposit, and the Zarafasaura fossil coming from a phosphate mining site.
Cryptoclidus was a smaller plesiosaur, though fairly typical in form. Cryptoclidus got its name from its very small collarbone, which is buried deep in the shoulder of the animal. This is in contrast to the human collarbone, which is readily visible on the upper thorax. The limbs of Cryptoclidus were very well suited to aquatic locomotion, as were most plesiosaurs by the Jurassic era.
The skull of Cryptoclidus looks formidable, but is actually quite fragile in build. This meant that Cryptoclidus, like most plesiosaurs, was not adept at tackling larger prey. Cryptoclidus probably restricted itself to small fish and squid, which its needle like teeth would have been well equipped at spearing and holding. Cryptoclidus’ sense of smell was also very acute, which would have allowed it to smell prey long before it heard or saw it.
There is some debate as to how much time Cryptoclidus spent in the water. A look at the trunk and limbs shows a fairly robust structure. The primary issues for a plesiosaur on land would be suffocation and poor locomotion. Poor locomotion meant that a Cryptoclidus sunning itself on a beach would be relatively easy prey for a large, land based predator.
The second problem, suffocation, was a larger issue. If Cryptoclidus were to pull itself onto land, most of its body mass would be centered on the torso and abdomen. This would put pressure on the lungs and inhibit breathing. Cryptoclidus was equipped with fairly strong limbs and gastralia (belly ribs) to counter this problem. Combined with its relatively small body mass, Cryptoclidus could have easily stayed on shore for extended periods of time without issue. This may have been a wise course of action, as Cryptoclidus shared its marine home with several large sharks and pliosaurs, either of whom could be a potential predator of Cryptoclidus.
Skeleton: By Ghedoghedo – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=28947498
Life Reconstruction: http://spinops.blogspot.com/2015/06/cryptoclidus-eurymerus.html