Plesiosaur Vertebra– The Backyard Fossil
At some point, every child becomes fascinated with dinosaurs, with their larger than life size and epic battles between predators (at least in the movies). Those same children probably dream about trekking through the desert to find a dinosaur buried in the ground. Well, for one such boy that dream came true…in his own backyard!
Sometime between the Late Triassic and Cretaceous periods, plesiosaurs (Cimoliasaurus magnus) roamed the waters of New Jersey2. Typically pictured as giraffes of the oceans with their long necks, the ones in New Jersey were actually short-necked. Unlike their long necked cousins, they are thought to be pursuit predators, chasing their prey, instead of lunging at them with their necks. This plesiosaur vertebra, whether part of the neck or body, was found by Tina Tobin’s son at their home in New Jersey. It was brought to us at Identification Day held at the American Museum of Natural History in New York City1.
Scanning fossils and other geological material is an integral part of our laboratory. Being able to see inside samples that are millions of years old, without damaging them, makes micro-CT imaging a valuable resource for Paleontologists and other researchers. Let us dig in and explore how this plesiosaur vertebra was imaged and explore what we were able to discover in the sample.
Scanning the Vertebra
The large size of the sample (approximately four inches in diameter) dictated that we scan it on our Bruker micro-CT 1173 system. The first stage in scanning is mounting the sample on a brass stage, with Styrofoam surrounding the sample for support. Styrofoam is used because it is lower in density than most of the objects we scan and therefore attenuates less X-Rays. When the scans are completed, the sample becomes the most prominent part of the image.
During the scan, the first images collected are called projection images; these are the series of 2D profiles that record the attenuation, or absorption of the X-Rays. These projection images are then converted from intensity readings into a series of axial slice images (cross sections) through Bruker’s NRecon software. Using the DataViewer software, the axial slice images can be converted to coronal or sagittal slice views. In Figure 1, we show a coronal slice to match the specimen orientation.
After obtaining the cross sections, Bruker’s CTVox software can compile them into 3-D virtual models with the ability to cut-away, rotate, and even create movies of the sample! Check out our video of the plesiosaur vertebra on the Micro Photonics YouTube channel.
Figure 1. Process of scanning to micro-CT images. Actual fossil (top, left), projection image of plesiosaur vertebra in scanner (top, right), image obtained after scanning, coronal slice (bottom, left), 3-D cut-away view done in CTVox visualization software (bottom, right).
The Unique Structure
Upon scanning this sample, we were impressed with how much trabecular and cortical bone is still intact (see Figure 2) in a bone that is millions of years old. The cortical bone is indicated by compact bone on the peripherals, whereas the trabecular is the more porous internal structure. Being able to see such detail in the bone structure can tell a lot about the forces at play on a bone. Dense trabecular, as seen here, can suggest that the plesiosaur vertebrae may have been exposed to quite a bit of compressive force. This may be helpful for paleontologist to better understand how the plesiosaur lived and interacted with its environment. This is truly an amazing find and it is impressive how well preserved the bone is after all these years!
Figure 2. Trabecular and cortical bone still visible in the plesiosaur vertebra.
It was an honor to be asked to participate in Indentification Day at The American Museum of Natural History and to be able to scan such interesting artifacts. We will have to look twice at the next rock we find in our backyard! If you have a fossil or unique sample that you would like us to scan for you, let us know; we would be glad to highlight you in the image of the month. Feel free to e-mail: firstname.lastname@example.org or call 610-366-7103 if you would like to submit a sample or learn more about our laboratory testing.
Thank you again to AMNH and to Tina Tobin for allowing us to bring the sample back to our lab for scanning.
NRecon, DataViewer, CTVox
Micro Photonics Imaging Laboratory, Allentown, PA
- Gallagher, William B. (1997). When Dinosaurs Roamed New Jersey. Rutgers University Press. Retrieved from: https://books.google.com/books?id=jo32Q2F6gMYC&pg=
- Whitley, John. (2015). Fossils of New Jersey: REPTILES AND Dinosaurs: Plesiosaur. Retrieved from: http://www.fossilsofnj.com/reptiles/plesiosaurs.htm