Pectinodon

MEANING: Comb tooth

PERIOD: Late Cretaceous

CONTINENT: North America

Pectinodon is known only from its comb-like serrated teeth, but it can be inferred from closely related troodontids that it was a swift feathered biped. Troodontids are known to have had unusually large brains with large forward-pointing eyes. This indicates that they had good binocular vision, and may have been able to see well in the dark.

Pectinodon is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known goups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene (K–Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K–Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Pectinodon is a troodontid. Troodontidae is a family of theropod dinosaurs which are closely related to birds. Many genera are known only from teeth, and this has led to much debate and reclassification over the course of the history of paleontology. The oldest definitive troodontid is known from the Late Jurassic of Wyoming. Over the Cretaceous, they radiated throughout western North America, Asia, and Europe, suggesting a mostly Laurasian distribution.

Troodontids are small, bird-like, gracile maniraptorans. They have unique skull features, such as large numbers of closely spaced teeth in the lower jaw. They are also equipped with sickle-claws and raptorial hands, similar to the closely related dromaeosaurs. Troodontids also had unusually large brains and eyes, suggesting that they were behaviourally advanced and had keen senses.