Size and Weight:
As far as paleontologists can tell, Achillobator (the name, "Achilles warrior," refers both to this dinosaur's large size and to the large Achilles tendons it must have had in its feet) was a raptor, and thus in the same family as Deinonychus and Velociraptor. However, Achillobator does appear to have had some quirky anatomical features (mainly concerning the alignment of its hips) that differentiated it from its more famous cousins, which has led some experts to speculate that it may be an entirely new type of dinosaur.
Like other raptors of the Cretaceous period, Achillobator is often depicted as sporting a coat of feathers, underlining its close evolutionary relationship with modern birds. However, this is based not any solid fossil evidence, but a presumed sharing of "featheriness" (either as juveniles or adults) by most small theropod dinosaurs.