Sinosauropteryx
"Sinosauropteryx" was a small bipedal theropod, noted for its short arms, large first finger (thumbs), and long tail. The taxon includes some of the smallest known adult non-avian theropod specimens, with the holotype specimen measuring only in length, including the tail. However, this individual was relatively young. The longest known specimen reaches up to in length, with an estimated weight of .
Spinosaurus
François Therrien and Donald Henderson, in a 2007 paper using scaling based on skull length, challenged previous estimates of the size of "Spinosaurus", finding the length too great and the weight too small. Based on estimated skull lengths of , their estimates include a body length of and a body mass of . The lower estimates for "Spinosaurus" would imply that the animal was shorter and lighter than "Carcharodontosaurus" and "Giganotosaurus". The Therrien and Henderson study has been criticized for the choice of theropods used for comparison (e.g., most of the theropods used to set the initial equations were tyrannosaurids and carnosaurs, which have a different build than spinosaurids), and for the assumption that the "Spinosaurus" skull could be as little as in length. Improvement of the precision of size estimates for "Spinosaurus" requires the discovery of more complete remains as available for some other dinosaurs, especially the limb bones of "Spinosaurus" which are "hitherto unknown".