Egg embryo is adequately developed it hatches, i.e. breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering. The largest recorded egg is from a whale shark, and was in size. Whale shark eggs typically hatch within the mother. At and up to , the ostrich egg is the largest egg of any living bird, though the extinct elephant bird and some dinosaurs laid larger eggs. The bee hummingbird produces the smallest known bird egg, which weighs half of a gram (around 0.02 oz). Some eggs laid
Largest prehistoric animals gruiform and largest phorusrhacid or "terror bird" (highly predatory, flightless birds of South America) was "Brontornis", which was about tall at the shoulder, could raise its head above the ground and could have weighed as much as . The immense phorushacid "Kelenken" stood tall with a skull long ( of which was beak), had the largest head of any known bird. The largest North American phorusrhacid is "Titanis", which is about tall, as tall as a forest elephant. The largest-known bird of prey ever was the enormous Haast's eagle ("Harpagornis moorei"), with a wingspan of , relatively short for their