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Mosasaurs (Mosasauridae)

Age – Late Cretaceous; Commonality – uncommon; Size – teeth: 1/4-2+ inches, vertebrae: 3/4-3+ inches (centrums)

Mosasaurs possessed two types of teeth: they had the usual upper and lower jaw teeth, but they also had a second set of teeth on a separate jaw behind their maxilla, which are called pterygoid teeth. These specialized pterygoid teeth were used to help hold down prey that was struggling to help make swallowing easier. Most mosasaur teeth have an elliptical base that has a wide but shallow indentation, two prominent carinae (some positions may have only one), and smooth enamel with no serrations on the carinae. However, since reptile teeth are variable, there are a lot of different exceptions. Some mosasaur teeth (especially pterygoid teeth) have a circular base and some teeth appear to have barely any basal indentation at all. Some mosasaur teeth have irregular, ridged enamel near the tips of the teeth (info from Steve B.). Some mosasaur teeth, especially some posteriors, can have microserrations on them. These serrations can make the tooth appear to be theropod.

Mosasaurs have an interesting way of tooth replacement. Instead of a new replacement tooth pushing an old one out from the bottom, a resorption pit forms where basically the new tooth swings into its upright position from its initial horizontal position, while the old tooth is discarded. This way of tooth replacement is found in snakes, making mosasaurs their distant relatives.

Mosasaur vertebrae are distinct when complete. They have a slightly concave anterior face and slightly convex posterior face. They can vary greatly in appearance depending on the position they came from (thoracic vertebrae differ from terminal vertebrae in size and process attachment, for example).

Other mosasaur bones are pretty rare. 

Teeth

Lateral View

Posterior View

Typical tooth. Most teeth are from Prognathodon sp. and Mosasaurus conodon. This one is probably M. conodon.

Lateral View

Lateral View

Anterior View

Posterior View

Basal View

An interesting “albino” Mosasaur tooth. This one seems like it is from Prognathodon sp.

Anterior View

Posterior View

Lateral View

Lateral View

This one has an unusual shape. It might be a pterygoid tooth.

Lateral View

Oblique View

An M. conodon tooth showing a classical wear pattern. Mosasaur teeth are very prone to splitting in half.

Lateral View

Lateral View

Anterior View

Mosasaur Cretaceous tooth, Monmouth County, New Jersey - Anterior View

Posterior View

Occlusal View

Mosasaur Cretaceous tooth, Monmouth County, New Jersey - Occlusal View

Basal View

A crazy tooth. This is a pathological anterior/lateral Prognathodon sp. tooth. It is extraordinarily rare to find a pathological Mosasaur tooth in such nice condition anywhere, especially in NJ. The tooth has 4 carinae instead of the normal 2. It also has a slight contortion and a slight flattening/indentation towards the base of the inner lateral surface. This pathology was caused by either an injury to the tooth germ, a feeding injury, not enough room for normal growth (which made it grow scrunched in the tight space), or maybe by the anterior side of the tooth lodging into the next tooth, making it grow awkwardly. The tooth also doesn’t seem to have any signs of occlusion by the tooth that would have been located in the same position as this tooth, just on the other jaw, or any apical wear (from feeding); this means that it was likely not in the usual erect position. ID by Lynn Harrell of the Alabama Geological Survey.

Lateral View

Lateral View

Posterior View

Posterior View

This tooth is likely a posterior. Posterior teeth are more distally curved. IDd with the help of John W.

Lateral View

Lateral View

Anterior View

Posterior View

Basal View

Occlusal View

This tooth is a posterior Prognathodon sp.

Anterior View

Posterior View

Lateral View

Basal View

Edit: Croc tooth. Will be moved.

Anterior View

Posterior View

Occlusal View

Basal View

Lateral View

Edit: Croc tooth. Will be moved.

Anterior View

Posterior View

Lateral View

Basal View

EDIT: Croc tooth. Will be moved. This one has some interesting sinusoid carinae.

Anterior View

Posterior View

Occlusal View

Lateral View

Basal View

EDIT: This is actually a Croc tooth. Will be moved.

Lateral View

Lateral View

Anterior View

Posterior View

Basal View

Occlusal View

This is an unusual Mosasaur tooth. It seems to be a replacement tooth with a partial root. It must be from a Mosasaur that died with it still in its jaw (that is the only way a replacement tooth can be found).

Vertebra

Caudal Aspect

Rostral Aspect

Dorsal Aspect

Ventral Aspect

Side View

Oblique View

Mosasaur Cretaceous terminal (posterior, caudal) vertebra - Monmouth County, New Jersey
Mosasaur terminal (posterior) vertebra. Posterior vertebrae have a different shape and aren’t as common as the more anterior types of vertebrae. This one still has the four processes attached.

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