Eggs of Different Animal Groups
Several major groups of animals typically have readily distinguishable eggs.
| Class | Types of eggs | Development |
|---|---|---|
| Jawless fish | Mesolecithal eggs, especially large in hagfish | Larval stage in lampreys, direct development in hagfish. |
| Cartilaginous fish | Macrolecithal eggs with egg capsule | Direct development, vivipary in some species |
| Bony fish | Macrolecital eggs, small to medium size, large eggs in the coelacanth | Larval stage, ovovivipary in some species. |
| Amphibians | Medium sized mesolecithal eggs in all species. | Tadpole stage, direct development in some species. |
| Reptiles | Large macrolecithal eggs, develop independent of water. | Direct development, some ovoviviparious |
| Birds | Large to very large macrolecithal eggs in all species, develop independent of water. | The young more or less fully developed, no distinct larval stage. |
| Mammals | Macrolecithal eggs in monotremes and marsupials, extreme microlecithal eggs in placental mammals. | Young little developed with indistinct larval stage in monotremes and marsupials, direct development in placentals. |
Read more about this topic: Egg (biology)
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