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 .
Nipponosaurus
The immature holotype specimen measures roughly four meters (13 feet) in length. When it was originally described, it was considered to be an adult, because of its co-ossified sacral vertebra. Future authors doubted this, merely citing its small size. In the 2004 redescription, it was examined more closely and several characteristics were found that identified it as an juvenile individual. Later, in 2017, another team re-evaluated the specimen, and determined through investigating the fossils at a microscopic level (in a process called histology) that this was correct, although they doubted the significance of some of the characters identified in the former study.