The Mosasaurus was one of the ocean’s most formidable hunters during the Late Cretaceous period, dominating the seas approximately 94 to 66 million years ago. This massive marine reptile belonged to the order Squamata, making it a relative of modern lizards and snakes. Mosasaurs evolved into apex predators, reaching lengths that could exceed 39 feet in the largest species, such as Mosasaurus hoffmannii. Their success depended heavily on powerful jaws and specialized teeth adapted for capturing and consuming large, struggling prey.
Counting the Teeth in the Jaws
The primary teeth fixed along the edges of the upper and lower jaws are known as marginal teeth. The exact number of these teeth varied based on the species and the size of the individual, but a consistent pattern exists across the genus Mosasaurus.
On the upper jaw, the teeth are divided between the premaxilla and the maxilla bones. A typical Mosasaurus had two teeth on the premaxillary bone at the tip of the snout, followed by a longer row of twelve to sixteen teeth on the maxillary bone on each side. The lower jaw features the dentary teeth, which typically ranged from fourteen to seventeen teeth per side.
To calculate the total count for the main biting surface, one must double these ranges to account for both the left and right sides of the mouth. For a single individual, the main jaw count could easily total between 56 and 70 teeth, depending on the species-specific count of the maxillary and dentary rows.
The Unique Pterygoid Teeth
The total tooth count for a Mosasaurus is significantly higher than the marginal jaw teeth alone, due to a secondary row of teeth located deep within the mouth. This specialized set of teeth is positioned on the pterygoid bone, which forms part of the palate or the roof of the mouth. The presence of these pterygoid teeth is a characteristic feature shared with modern snakes and certain lizards, underscoring the evolutionary link between mosasaurs and other squamates.
These teeth are often overlooked in a simple count, as they are not part of the primary cutting and grasping action of the jaws. Instead, their function was focused on the process of swallowing. They were typically smaller and more recurved than the main jaw teeth, acting as inward-pointing hooks. As the Mosasaurus captured prey, the pterygoid teeth would grip the animal and help ratchet it down the throat, preventing escape.
A typical Mosasaurus species would have between eight and sixteen pterygoid teeth on each side of the upper jaw. This adds sixteen to thirty-two teeth to the total count, bringing the complete number of teeth in a fully dentulous Mosasaurus well over eighty.
Structure and Replacement of Mosasaurus Teeth
The individual teeth of a Mosasaurus were robust structures designed for a hypercarnivorous diet. Most teeth were conical in shape and featured a prismatic enamel surface, which provided exceptional strength. A defining feature was the presence of two opposite cutting edges, known as carinae, running vertically down the tooth crown. These carinae acted like blades, helping the predator slice through the flesh of its prey.
The teeth were set in deep sockets within the jawbone, a condition known as thecodont dentition. Mosasaurs were polyphyodont, meaning they continuously replaced their teeth throughout their lives. This constant replacement ensured that their primary hunting tools remained sharp and functional.
The replacement process involved an eight-stage cycle where a new tooth developed within a specialized pit at the root of the original tooth. The replacement tooth would grow from below and then swing into its upright, functional position, pushing the old tooth out of the jaw. This process of shedding and regrowth allowed the Mosasaurus to maintain its predatory efficiency throughout its life.