Awesome Mosasaur (Prognathodon) Jaw Section - 7.4"

This is a really cool fossil of Prognathodon, a very large type of Mosasaur. It's a section of jaw still in the original matrix that shows a pair of it's extremely large teeth, but more interestingly you can see one of the unerupted, replacement teeth growing inside the jaw. Mosasaur's like dinosaurs and sharks replaced their teeth frequently as they become worn or broken. There were teeth continuously growing inside the jaw bone, underneath and to the side the visible teeth which could move into place when tooth was lost.

Another feature that makes this specimen so unique is that it has NO RESTORATION or COMPOSITING and the quality of preparation is outstanding. Mosasaurs jaws are almost always found crushed and fragmented. Whenever you see one that looks in it's in a life-like state it's because it's been put back together, missing pieces often restored, and teeth often composited. This specimen is in it's natural state, just with superb preparation work done to remove the matrix from around it.

Mosasaurs are a family of enormous marine reptiles that truly dominated the seas 90 million years ago. They ruled during the last 20-25 million years of the Cretaceous period. With the extinction of the ichthyosaurs and decline of plesiosaurs, mosasaurs diversified to become prolific apex predators in nearly every habitat of the oceanic world.

Artists reconstruction of the mosasaur Prognathodon saturator.
Artists reconstruction of the mosasaur Prognathodon saturator.

Larger mosasaurs were the great leviathans of their time, extending 10–15m, or 33–49ft long. Hainosaurus holds the record for longest mosasaur, at a seemingly impossible 57ft. The smaller genera were still an impressive 10–20ft long. Mosasaurs probably evolved from semi-aquatic scaled reptiles which were more similar in appearance to modern-day monitor lizards. They had double-hinged jaws and flexible skulls (much like that of a snake) which enabled them to gulp down their prey almost whole.

The gruesome unchewed contents of fossilized mosasaur guts have revealed a varied diet of sea birds, ammonites, smaller marine lizards, possibly shark, and even other mosasaurs. Ammonites were especially crunchy mosasaur treats. They were abundant in the Cretaceous sea, and some Mosasaurs had specialized teeth for the job.

Mosasaurs probably lurked for an ambush, rather than hunt, possibly using their powerful tail flukes for extra thrust to dart out and swallow unsuspecting prey. Non-reflective, keeled scales may have been a great advantage to the Mosasaur sneak-attack.

Mosasaurs breathed air and gave birth to live young. The bronchi leading to the lungs run parallel to each other instead of splitting apart from one another as in monitors and other terrestrial reptiles. They were well-adapted to living in the warm, shallow, epicontinental seas of the period.

Although Mosasaurs diversified and proliferated at a spectacular rate, their specialization is considered the source of their demise when marine systems collapsed at the end of the Cretaceous.
Prognathodon sp.
Oulad Abdoun Basin, Morocco
Phosphate Deposits
Specimen 7.4" Long, 7" Tall, 3.8" Deep
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