The largest dinosaur egg to date is about 12 inches (30 centimeters) long and 10 inches (25 centimeters) wide; it may have weighed about 15.5 pounds. It is thought to be from a giant, 100-million-year-old herbivore called a Hypselosaurus. To compare, the prize for the largest bird egg (and largest flightless bird) on Earth belongs to the African ostrich, with eggs up to 6.8 inches (17 centimeters) long by 5.4 inches (14 centimeters) wide, and weighing up to 3.3 pounds.