Mosasaur Jaw

Marine Fossil

Scientific Name: Mosasaurus

Mosasaurs were top predators of the Cretaceous sea. They had a set of large, cone shaped teeth used to hunt ammonoids, an extinct relative of today’s squids. Mosasaurs are most closely related to Varanid lizards, such as the Komodo dragon and grew up to 15 meters (50 feet) long. Few fossils of mosasaurs have been discovered in New Mexico, but this crushed Mosasaur dentary (jaw) shows just how large these predators were. This fossil was found on a fallen sandstone slab near the Petroglyph Trail at Chaco Culture National Historical Park.

3D Mosasaur Jaw—Mosasaurus

Chaco Culture National Historical Park, New Mexico

Alternative Text for the 3D Model

A 3D model. This model shows a rock slab with a fossil exposed on the surface. The model can be rotated and tilted using a computer interface.

Footnotes linked to the model:

Where are the teeth? This jaw fragment was found in isolation on the side of a fallen sandstone slab. In life, the mosasaur’s conical teeth probably sat in these dark grooves(?). These specific teeth have not yet been found, but lone mosasaur teeth have been found eroding from sandstone in other parts of Chaco.

Under pressure: A lot can happen to change the original shape of an organism. Rapid burial is a key part in fossilization, but this process can also crush the organism due to intense pressure. Paleontologists must be detectives and look for clues that help them imagine what the creature looked like even when their remains are broken or incomplete.

Footnotes:

Where are the teeth? This jaw fragment was found in isolation on the side of a fallen sandstone slab. In life, the mosasaur’s conical teeth probably sat in these dark grooves(?). These specific teeth have not yet been found, but lone mosasaur teeth have been found eroding from sandstone in other parts of Chaco.

Under pressure: A lot can happen to change the original shape of an organism. Rapid burial is a key part in fossilization, but this process can also crush the organism due to intense pressure. Paleontologists must be detectives and look for clues that help them imagine what the creature looked like even when their remains are broken or incomplete.

Fossil Remains

Left image

Mosasaur feeding on ammonites.

Right image

Outlined in orange is an approximation of the fossil that was preserved.

Credit: Illustration by Karen Carr.

The mosasaur went extinct at the end of the Cretaceous period. Outlined in orange is an approximation of the fossil that was discovered at Chaco. Complete jaw fossils have been found, but they are much more rare.

Related Links

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

Part of a series of articles titled
Chaco Collections—Paleontology.

Previous:
Late Cretaceous Ammonite

Next:
Plesiosaur Bone Fossil

Where this belongs

• Chaco Culture National Historical Park

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