Cretaceous Blue Moon, by Robert Nicholls | Tumblr | Facebook.

“By the light of the moon a spectacular annual gathering of Elasmosaurus platyurus takes place. Their courtship requires them to raise their long necks high out of the water to display their strength and suitability for mating. Remarkably the elasmosaurs chose this particular time and place because it coincides with a seasonal bloom of bioluminescent plankton, which make them glow blue.

I first sketched this idea in 2006-2007ish. I would like to be able to say this is the first artwork illustrating _Elasmosaurus_ using their necks this way but I was too slow to producing this image and the brilliant John Conway beat me to it. Nevertheless, the composition is completely unique and I am pretty sure a bioluminescent gathering is a first in the world of paleoart!”

Marine Reptile Month #12 – Hydrotherosaurus

Late Cretaceous period (72-66 mya)

One of the larger elasmosaurid plesiosaurs, Hydrotherosaurus reached lengths of around 13m (42ft 7in). And, like the unrelated Tanystropheus, about half of that was neck – although Hydrotherosaurus had 60 cervical vertebrae compared to Tanystropheus’ 10-12.

Although often depicted with swan-like or snake-like highly flexible necks, elasmosaurs weren’t actually capable of such extreme postures. Their necks seem to have been relatively stiff, and may have functioned as rudders – turning the head towards something would cause the whole body to move in that direction.

The lifestyle of these animals is still a little unclear. They’ve been proposed as “spear fishers”, sticking their long necks and heads into schools of fish to snatch up prey before the main bulk of their bodies became visible. Stomach contents of seafloor crustaceans and molluscs, along with trace fossils of odd gutter-like gouge marks, however, raise the possibility of elasmosaurs instead scooping up mouthfuls of prey-rich sediment.

There’s also some fun speculation about the necks being electric organs.

Color palette used: “Revenge of the Sunfish