The smallest dinosaur ever discovered is a subject of debate among scientists. However, there are several contenders for the title:

• Oculudentavis: This dinosaur was discovered in Myanmar and is almost perfectly preserved in amber. It was about the size of a bee hummingbird, making it the smallest dinosaur discovered yet. However, recent research has suggested that Oculudentavis may not be a bird at all, but rather a lizard.

• Microraptor: This dinosaur is the smallest known species of raptor dinosaur, weighing about two pounds and only a foot tall.

• Pendraig milnerae: This dinosaur was found in a Welsh quarry and is thought to have been about the size of a chicken, measuring just one meter in length (including its tail) .

• Compsognathus: This dinosaur grew only about as large as a chicken, but with a length of about 60-90 cm (2-3 feet), including the long tail, and a weight of about 5.5 kg (12 pounds) .

Its worth noting that the classification of some of these dinosaurs as "smallest" is somewhat subjective, as there were likely many other small dinosaur species that have yet to be discovered.