Plesiosaur Bone Fossil

Like many birds and large swimmers today, it is thought that the plesiosaur ingested rocks to aid in digestion.

NPS illustration.

Marine Fossil
Scientific Name: Plesiosauria

This fossil may be a shoulder blade, or scapula, from a large marine reptile, such as a plesiosaur. If identified, it would be one of very few plesiosaur fossils in the entire state of New Mexico. Plesiosaurs are long-necked ambush predators who hunted schools of small fish, ammonites, and other invertebrates. Many plesiosaur skeletons have been found with round, smooth stones called gastroliths in or near their abdomens, suggesting these animals swallowed them to aid with digestion. Sometimes over 100 rocks have been found in association with a single plesiosaur. Many animals do this today, including active swimmers like crocodiles and penguins, as well as ground-dwelling birds chickens and ostriches.

3D Plesiosaur Bone Fossil—Plesiosauria
Chaco Culture National Historical Park, New Mexico

_{Plesiosaur Bone Fossil by National Park Service Geologic Resources Division on Sketchfab}

Alternative Text for the 3D Model

A 3D model. This model shows a fossil in a rock slab. The model can be rotated and tilted using a computer interface.

Footnotes linked to the model:

1. Scale marker.
2. Scale marker.
3. Peeking through the sand - middle of the bone—This bone is covered by a sandstone concretion and cemented to the ground, making it difficult to identify or collect. However, some of the actual bone is exposed in the middle of the plate.
4. Ocean Locomotion—The flat shape of this bone resembles the shoulder blade of a large marine reptile, which were used for powerful swimming. Plesiosaurs paddled using four large fins in a kind of underwater flight, similar to the movements of a dragonfly1.

Footnotes

1. Scale marker.
2. Scale marker.
3. Peeking through the sand - middle of the bone—This bone is covered by a sandstone concretion and cemented to the ground, making it difficult to identify or collect. However, some of the actual bone is exposed in the middle of the plate.
4. Ocean Locomotion—The flat shape of this bone resembles the shoulder blade of a large marine reptile, which were used for powerful swimming. Plesiosaurs paddled using four large fins in a kind of underwater flight, similar to the movements of a dragonfly¹.

Related Links

• NPS—Chaco Culture National Historical Park
• NPS—National Fossil Day
• NPS—Photogrammetry
• NPS—Fossils and Paleontology
• NPS—Geology

¹National Geographic: https://video.nationalgeographic.com/video/101-videos/00000165-1fd4-d579-ab65-3fd4d1cd0000