This week’s “What Is It Wednesday” was a close-up shot of the ventral surface of our juvenile plesiosuar, Mauisaurus, on display next to Styxosaurus, SDSM 451, in the Museum of Geology. It includes a portion of the spinal column, numerous ribs, girdle elements, and portions of a flipper.
The specimen was recovered in 2005 by a joint SDSMT and Eastern Washington University expedition to Vega Island, Antarctica. It was discovered by SDSMT geology professor Dr. Foster Sawyer on Sandwich Bluff (Martin et al., 2007). This specimen is one of very few juvenile plesiosaurs recorded worldwide. While other plesiosaurs have been recovered from Antarctica (Kelner et al., 2011), this is the only juvenile recorded from the southern end of the world.
What was pictured on Wednesday were the interlacing gastralia, or belly ribs. Gastralia are common in many reptiles, and serve as extensions of the lateral ribs around the ventral surface of the animal to provide support and protection to the abdominal cavity. Gastralia are common in plesiosaurs, and can be seen in SDSM 451 as well.
This specimen was also associated with gastroliths, or belly stones. It would seem that the phenomenon of plesiosaurs swallowing stones either to aid in digestion or affect neutral buoyancy is not unique to North American taxa, nor to adults. Gastroliths appear to have been an integral part of plesiosaur biology.
J. E. Martin, J. F. Sawyer, M. Reguero and J. A. Case. 2007. Occurrence of a young elasmosaurid plesiosaur skeleton from the Late Cretaceous (Maastrichtian) of Antarctica. U.S. Geological Survey and The National Academies Short Research Paper 66:1-4
Alexander Wilhelm Armin Kellner, Tiago Rodrigues Simoes, Douglas Riff, Orlando Grillo, Pedro Romano, Helder de Paula, Renato Ramos, Marcelo Carvalho, Juliana Sayao, Gustavo Oliveira1 & Taissa Rodrigues. 2011. The oldest plesiosaur (Reptilia, Sauropterygia) from Antarctia. Polar Research. 30:1-6