It is interesting to compare the dentition and arms of these three dinosaurs. Allosaurus, or a T. rex-like dinosaur, had sharp pointy teeth. The Alvarezsaur, Haplocheirus, had many shorter teeth, and the most bird-like dinosaur of the group, Shuvuuia, had reduced peg-like dentition. Also note the three claws of roughly equal size of the Allosaurus, the thick short thumb and two skinny fingers of Haplocheirus, and the completely reduced single digit of Shuvuuia.
Image Courtesy of Zina Deretsky, National Science Foundation