Monday, 28 October 2019

MARINE REPTILES OF THE WESTERN INTERIOR SEAWAY

During the Cretaceous Period, the Western Interior Seaway split North America into two landmasses. Part of the seaway was the Bearpaw Sea, a warm, shallow sea that covered 1.7 million square kilometres of coastal plain about 74 million years ago.

It was home to many marine reptiles, ammonites, fishes, and other aquatic life. Elasmosaurs (long-necked plesiosaurs) were one group of marine reptiles that inhabited prehistoric waters. They were primarily fish eaters, and used their long necks to strike at fish, then trapped them in their interlocking teeth. A new genus and species of elasmosaur, Albertonectes vanderveldei, was uncovered in 2007 during routine ammonite shell mining.

Albertonectes has 76 neck vertebrae, the most of any animal known. (Compare this to giraffes that only have seven neck vertebrae. Albertonectes had a neck that was 6.5 metres long. Was it flexible and able to bend sharply and quickly? Or was it stiff, with a gentle arc that could cover a large area? Paleontologists used computer modelling to study the neck’s flexibility. The neck broke into four segments when it collapsed on the seafloor. This indicates that it was rigid enough to break easily and supports the hypothesis for having a stiff neck.

Another hypothesis is that gastroliths were used for digestion. Living animals that have gastroliths normally eat seeds, fruits, or tough vegetation. Since flesh is easier to digest than plant tissue, a carnivorous elasmosaur probably wouldn’t have needed gastroliths to grind up its food.

This incredible specimen provides insight into what marine communities were like during the Cretaceous Period. The fossilized remains of other animals that lived alongside Albertonectes are found in the rocks formed at the bottom of the Bearpaw Sea.

These included potential prey such as small fishes, ammonites, and crayfish. From recovered shark teeth, and tooth marks left on bone, palaeontologists determined that the carcass of Albertonectes was scavenged by one or more sharks. Read more on this impressive find at:
https://royaltyrrellmuseum.wpcomstaging.com/…/albertonecte…/