Description and Classification

Because Aublysodon is primarily known from teeth, a full description of the animal is uncertain. The type teeth of Aublysodon mirandus are small, D-shaped in cross-section (incisiform), and lack the typical serrations (saw-like edges) found on the teeth of many carnivorous dinosaurs. If Aublysodon represented a distinct adult animal, it would have been a relatively small theropod, perhaps around 2 to 4 meters (6.5 to 13 feet) in length. Like other tyrannosauroids, it would have been a bipedal carnivore, walking on two legs, with short arms and a large head.

In terms of classification, Aublysodon belongs to the group Theropoda, specifically within the superfamily Tyrannosauroidea, which includes Tyrannosaurus rex and its relatives. Historically, some paleontologists proposed a distinct subfamily called Aublysodontinae for Aublysodon and similar forms. However, this classification is no longer widely accepted. Most researchers now believe that the features of Aublysodon teeth, particularly their small size and lack of strong serrations, are characteristic of young tyrannosaurids. As these animals grew, their teeth would have changed in shape and developed more pronounced serrations. Therefore, Aublysodon is generally not considered a valid genus, but rather a historical name applied to what were likely young individuals of other tyrannosaur species.

Distinguishing Features

The features historically used to identify Aublysodon are almost entirely based on its teeth. If it were a distinct genus, its distinguishing features would include:

• Teeth from the front of the upper jaw (premaxillary teeth) that are D-shaped in cross-section.
• A lack of serrations, or very fine serrations, on the cutting edges of these teeth, which is unusual for most adult tyrannosaurids.
• Relatively small tooth size compared to adult specimens of larger tyrannosaurids like Gorgosaurus or Daspletosaurus.

It is important to remember that these features are now largely understood to be common in juvenile tyrannosaurids, which makes it difficult to identify Aublysodon as a separate and unique dinosaur.

Paleoenvironment and Diet

Fossils attributed to Aublysodon have been found in formations like the Judith River Formation of Montana, dating to the Campanian stage of the Late Cretaceous. During this time, this region of North America was a coastal plain with rivers, swamps, and forests, bordering the Western Interior Seaway. The climate was warm and humid, supporting a rich ecosystem.

Aublysodon would have shared its environment with a diverse range of other dinosaurs. These included large herbivorous hadrosaurs (duck-billed dinosaurs) like Maiasaura and Gryposaurus, horned ceratopsians such as Avaceratops and Centrosaurus, armored ankylosaurs, and various smaller plant-eating dinosaurs. Other carnivores in this ecosystem included larger tyrannosaurids (which Aublysodon teeth might actually represent), as well as smaller predators like dromaeosaurids (“raptors”) and troodontids.

As a carnivore, whatever animal the Aublysodon teeth belonged to would have eaten meat. If Aublysodon was a distinct, small predator, it might have hunted smaller dinosaurs, lizards, and mammals. If, as is more likely, the teeth belong to young individuals of larger tyrannosaurids, their diet would have consisted of smaller prey than the adults, possibly focusing on juvenile dinosaurs or smaller animal species until they grew large enough to tackle bigger game.

Significance and Ongoing Research

Aublysodon holds historical significance as one of the earliest named tyrannosauroid dinosaurs from North America. However, its primary legacy today is as an example of a “tooth taxon” – a genus named solely on the basis of teeth. Such taxa are often problematic because teeth alone can be variable within a single species (due to age or position in the jaw) and similar across different related species, making definitive identification difficult without more complete skeletal material.

The ongoing research related to Aublysodon largely focuses on understanding tyrannosaurid growth and development (ontogeny). By studying how the teeth of known tyrannosaurids like Gorgosaurus, Daspletosaurus, and Tyrannosaurus rex changed as the animals grew from juveniles to adults, paleontologists can better determine if Aublysodon-type teeth simply represent an early growth stage of these larger dinosaurs. Most current scientific consensus leans towards this interpretation, meaning that Aublysodon is not a valid biological entity but rather a name applied to the teeth of young tyrannosaurs. This re-evaluation helps to provide a clearer picture of tyrannosaur diversity and evolution during the Late Cretaceous period and highlights the importance of complete fossil specimens in understanding prehistoric life.