Atrociraptor

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Pennaraptora > Paraves > Dromaeosauridae > Eudromaeosauria > Saurornitholestinae

Overview: Dromaeosaurids, or “raptor” dinosaurs, are split into a few major lineages. Those found to be particularly derived belonged to the subgroup Eudromaeosauria, which is itself split into three main subfamilies – the Velociraptorinae, Dromaeosaurinae and Saurornitholestinae. Atrociraptor is currently classified as a saurornitholestine, though it was originally seen as a velociraptorine. Most of the traits that distinguished saurornitholestines could be found on their skulls, which were usually fairly deep and robust, and their teeth. The anatomy of their sinuses was also apparently different from that of other dromaeosaurids. Still, in most respects, Atrociraptor and its relatives had similar anatomies to other “raptors”, being highly birdlike, bipedal predators with enlarged talons set onto the second toe of each foot. With a length of about two meters, Atrociraptor was similar in size to the famous Velociraptor, but it’s presumed to have been a more heavily built animal.

Atrociraptor is currently only known from parts of its snout and jaws, so restorations of its overall body have to rely on what we see on its relatives, like Saurornitholestes. Even for a member of the Saurornitholestinae, Atrociraptor had a notably tall snout. One of its more unique features was the form of its teeth, which were raked strongly backwards and didn’t vary so much in size. It probably preyed on mostly smaller-sized animals, though groups could possibly take down larger prey. There is actually relatively scant evidence for pack hunting among dromaeosaurids, despite the behavior being so commonly depicted in media. Its enlarged “killing claws” allowed it to pin down small prey or to grip into the flesh of its larger victims. Atrociraptor was first discovered by an amateur fossil hunter in Alberta, Canada, in the mid-1990’s. It’s known from the Horseshoe Canyon Formation, so it likely lived alongside Albertosaurus, Struthiomimus, Pachyrhinosaurus, and Edmontosaurus.