There is some disagreement as to the smallest dinosaur fossil yet found. To date, the best contender for the smallest is the Microraptor (“little plunderer”), a bird-like (crow-sized) dinosaur from China, a coelurosaurid theropod about 16 inches (40 centimeters) long. Another vote for the smallest adult dinosaur fossil found to date is the Compsognathus (“pretty jaw”). This animal was slightly larger than a turkey, with a total length of approximately 3 feet (1 meter), and weighed approximately 6.5 pounds (2.9 kilograms). This small carnivore, nicknamed “Compy,” lived during the Jurassic period and was a fast-running, agile predator that probably subsisted on insects, frogs, and small lizards.

There was once another claim for smallest dinosaur fossil: the Mussaurus, or “mouse lizard,” was found in 1979 in South America. Once thought to be the smallest dinosaur, it is now known that the Mussaurus fossils were actually hatchlings of Coloradisaurus, which, when fully grown, would be larger than a Compsognathus. Their eggs were only 1 inch (2.54 centimeters) long; the fossil hatchlings were only 7.8 to 16 inches (20 to 40 centimeters) long.