Description and Classification

The only known fossil of Diplotomodon is its holotype, specimen ANSP 9680, which is a single tooth. The tooth is relatively large, conical, and somewhat flattened from side to side. Leidy noted its “double-edged” or “double cutting” nature, which refers to the presence of sharp cutting edges (carinae) on the front and back of the tooth, a common feature in many predatory reptiles.

When Joseph Leidy first described Diplotomodon, he cautiously suggested it might be related to marine reptiles like Mosasaurus. Later, other paleontologists, including Edward Drinker Cope, suggested it might be a carnivorous dinosaur, similar to Megalosaurus. However, without more complete fossil material, it is very difficult to determine its true affinities. Today, most paleontologists agree that the tooth is too generic to be assigned to a specific kind of animal with certainty. It could belong to a theropod dinosaur, a plesiosaur, a mosasaur, or even a large crocodilian, all of which lived during the Late Cretaceous and possessed similar types of teeth. Because of this uncertainty, Diplotomodon is considered a nomen dubium.

Distinguishing Features

Given that Diplotomodon is known only from a single tooth, its distinguishing features are limited to what can be observed from this sole piece of evidence. These include:

• A single known fossil specimen: a tooth.
• The tooth is relatively large and robust.
• It is conical in overall shape but is somewhat compressed (flattened side-to-side).
• The tooth possesses two opposite cutting edges (carinae), which inspired its name meaning “double cutting tooth.”

These features are not unique enough to confidently distinguish Diplotomodon from various other predatory reptiles of the Late Cretaceous period.

Paleoenvironment and Diet

The tooth of Diplotomodon was discovered in the Greensand formations of New Jersey. During the Late Cretaceous, this area was a shallow marine environment, part of a larger seaway covering much of North America’s Atlantic coast. The habitat would have included warm coastal waters, estuaries, and deltas. This environment was rich in marine life, including various fish, sharks, ammonites, and large marine reptiles like mosasaurs (such as Mosasaurus itself) and plesiosaurs (like those in the Elasmosauridae family).

Based on the tooth’s features—sharp, pointed, and with cutting edges—Diplotomodon was undoubtedly a predator. If it was a marine reptile, its diet would have consisted primarily of fish, squid, and potentially other marine animals. If it was a terrestrial dinosaur whose remains washed out to sea, it would have preyed on other dinosaurs or land animals. However, given the marine environment where the tooth was found, a marine animal is a more likely candidate.

Significance and Ongoing Research

Diplotomodon holds minor historical significance as one of the many fossil reptiles named during the early period of paleontological discovery in North America in the 19th century. It highlights the challenges faced by early paleontologists when working with incomplete and isolated fossil remains. The story of Diplotomodon serves as a good example of why paleontologists prefer more complete skeletons to confidently name and classify new species.

There is no specific ongoing research focused on Diplotomodon itself, primarily because it is a nomen dubium based on such limited material. Discoveries of more complete specimens from the same New Jersey formations could potentially help identify what kind of animal the Diplotomodon tooth belonged to. However, even if the tooth could be assigned to a known species of marine reptile or dinosaur, the name Diplotomodon itself would likely remain dubious unless a more distinctive holotype associated with skeletal material could be found. Its main value today is in the context of understanding the history of paleontological science and the fossil record of the Late Cretaceous marine ecosystems of eastern North America.