| Owing to the development of the common iliac veins there is no renal portal system like that of the Reptilia and Amphibia. |
| The ovum has in all Reptilia a very similar structure to that in Birds. |
| There are no vomerine, palatine, or pterygoid teeth, such as are met with in Amphibia and Reptilia. |
| By this convention, birds are considered Reptilia, just like bats are mammals and snails are mollusks. |
| In the case of Reptilia the anterior two or three segmental tubes in the region of the testis probably have this function. |
| Other examples are afforded by the alimentary tract of some of the Amphibia and Reptilia. |
