Dromaeosaurus
The relationships of Dromaeosaurus are unclear. Although its rugged build gives it a primitive appearance, it was actually a very specialized animal. It is usually given its own subfamily, the Dromaeosaurinae; this group is thought to include Utahraptor, Achillobator, Adasaurus, and possibly Deinonychus. However, the relationships of dromaeosaurs are still in a state of flux.