1. Anamniotic eggs: These are eggs that lack an amnion, which is a membrane that surrounds the embryo and provides it with a fluid-filled environment. Anamniotic eggs are found in amphibians and some fish.
2. Sauropsidan eggs: These are eggs that have an amnion, as well as a chorion, which is another membrane that surrounds the embryo and helps to protect it. Sauropsidan eggs are found in reptiles and birds.
3. Mammalian eggs: These are eggs that have an amnion and a chorion, as well as a placenta, which is an organ that connects the embryo to the mother and allows for the exchange of oxygen, carbon dioxide, and nutrients. Mammalian eggs are found in mammals.
Vertebrate eggs vary greatly in size, shape, and color, depending on the species. For example, the smallest vertebrate eggs are found in some frogs, which measure only a few millimeters in diameter, while the largest vertebrate eggs are found in some birds, such as the ostrich, which can measure over 15 centimeters in diameter.