Description and Classification

Pectinodon was a small, lightly built carnivorous dinosaur, characteristic of the troodontid family. Estimates suggest it grew to about 1 to 1.5 meters (3 to 5 feet) in length and would have been a fast and agile hunter. Like other troodontids, Pectinodon was likely covered in feathers and possessed a slender body with long legs. Troodontids are notable for having relatively large brains compared to their body size among non-avian dinosaurs, indicating they were probably quite intelligent creatures and had keen senses. They are classified within the group Maniraptora, which includes birds, making them close relatives of modern avian species.

Pectinodon belongs to the family Troodontidae. For many years, teeth like those of Pectinodon were often assigned to the genus Troodon. However, Troodon itself has become a problematic name, as it was also based on isolated teeth, and many paleontologists now consider it a “nomen dubium” (doubtful name). Discoveries of more complete skeletal material associated with “comb-like” teeth have helped to better define genera such as Pectinodon and distinguish it from other North American troodontids like Stenonychosaurus.

Distinguishing Features

Pectinodon can be identified by several key characteristics, primarily related to its teeth and general troodontid anatomy:

• Teeth: The most defining feature of Pectinodon is its teeth. They are relatively small but have very large, recurved (curved backward) denticles (serrations) on the posterior (back) edge, giving them a comb-like appearance. These denticles are proportionally larger than those found in many other troodontids.
• Large Eyes: Like other troodontids, Pectinodon likely had large, forward-facing eyes, which would have provided good depth perception and possibly excellent vision in low-light conditions.
• Slender Build: It had a gracile, bird-like skeleton with long, slender legs built for speed.
• Sickle Claw: Troodontids, including possibly Pectinodon, had a hyperextensible “sickle claw” on the second toe of each foot, similar to but generally smaller and less developed than those of their dromaeosaur relatives like Velociraptor.

Paleoenvironment and Diet

Pectinodon lived in the Late Cretaceous ecosystems of western North America, just before the mass extinction event that wiped out the non-avian dinosaurs. These environments, such as those represented by the Hell Creek and Lance Formations, were diverse, featuring coastal plains, river systems, forests, and swamps. Pectinodon shared its habitat with a wide array of other dinosaurs, including famous species like Tyrannosaurus rex, Triceratops, and Edmontosaurus, as well as various mammals, birds, reptiles, and amphibians.

As a small theropod, Pectinodon was likely a carnivore or possibly an omnivore. Its sharp, serrated teeth would have been effective for tearing flesh, suggesting a diet of small animals such as lizards, mammals, amphibians, and perhaps young dinosaurs or eggs. Its potential for good night vision might imply that it was active during twilight or at night, hunting smaller prey that was less active during the day.

Significance and Ongoing Research

The study of Pectinodon is significant for understanding the diversity and evolution of small theropod dinosaurs in North America during the final stages of the Cretaceous period. Its distinctive teeth help paleontologists identify troodontid presence even from fragmentary remains, which are common in fossil beds. The classification and relationships of troodontids like Pectinodon have been a subject of ongoing research. Initially, many troodontid teeth from North America were lumped into the genus Troodon, but further studies have shown that there was greater diversity, with Pectinodon representing one of these distinct forms.

Ongoing research continues to refine our understanding of Pectinodon‘s anatomy, behavior, and its precise place within the troodontid family tree. Future fossil discoveries, particularly more complete skeletons, will be crucial for painting a fuller picture of this agile, “comb-toothed” dinosaur and its role in the ancient ecosystems it inhabited just before the end of the Age of Dinosaurs.