Sinosauropteryx
"Sinosauropteryx" was a small theropod with an unusually long tail and short arms. The longest known specimen reaches up to in length, with an estimated weight of It was a close relative of the similar but older genus "Compsognathus", both genera belonging to the family Compsognathidae. Only one species of "Sinosauropteryx" has been named: "S. prima", meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered. Three specimens have been described. The third specimen previously assigned to this genus represents either a second, as-yet unnamed species or a distinct, related genus.
Compsognathidae
The other genera in this family are slightly larger than "Compsognathus longipes", but generally similar in size. The largest member of the family Compsognathidae is "Huaxiagnathus", which is estimated from its holotype to be around 5.9 m in length. "Sinocalliopteryx" measures around 2.4 m in length. "Sinosauropteryx" is the most similar to "Compsognathus", measuring at 1.07 m in length at most.