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.
Tyrannosaurus
"Tyrannosaurus rex" was one of the largest land carnivores of all time; the largest complete specimen, located at the Field Museum of Natural History under the name FMNH PR2081 and nicknamed Sue, measured long, and was tall at the hips, and according to the most recent studies estimated to have weighed between to when alive. Not every adult "Tyrannosaurus" specimen recovered is as big. Historically average adult mass estimates have varied widely over the years, from as low as , to more than , with most modern estimates ranging between and .
The neck of "Tyrannosaurus rex" formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs had only two clawed fingers, along with an additional small metacarpal representing the remnant of a third digit. In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso and to provide space for massive locomotor muscles. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollowed, reducing its weight without significant loss of strength.