Egg size and structure reflect important constraints on the reproductive and life-history characteristics of vertebrates(1). More than two-thirds of all extant amniotes lay eggs(2). During the Mesozoic era (around 250 million to 65 million years ago), body sizes reached extremes
egg is laid and hatches immediately(7).
A fossil egg unearthed from Cretaceous deposits in Antarctica is more than 20 cm long, exceeds all known nonavian eggs in volume, is soft-shelled, and was perhaps laid by a giant marine lizard such as a mosasaur.
