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.
Sauropoda
Neosauropoda is quite plausibly the largest clade of dinosaurs ever to have existed, with a few exceptions. Most exceptions are hypothesized to be caused by island dwarfism, although there is a trend in Titanosauria towards a smaller body size. The titanosaurs, however, have also been some of the largest sauropods ever. Other than titanosaurs, a clade of diplodocoids, a group of giants, called Dicraeosauridae, is diagnosed by a small body size. No sauropods were very small, however, for even "dwarf" sauropods are larger than , a size reached by only about 10% of all mammalian species.