Size and Weight:
As an example of how confusing the classification of theropod dinosaurs can be, many of these bipedal predators have been mistakenly diagnosed as raptors (which also fit under the theropod umbrella). Oddly, though, paleontologists didn't make that mistake with Noasaurus, even though this pint-sized carnivore may have had large, curved, single claws on its feet, a raptor-like trait if ever there was one.
Today, opinion is divided about where Noasaurus' giant claws belong (they were dug up apart from the rest of its fossil, hence the dilemma). Some paleontologists vote for this theropod's feet, and others for its hands; pending further fossil discoveries (with the claws firmly in place, of course) we may never know for sure.