Strange sharks, giant insects, and a new and improved egg
During the carboniferous, forests and swamp dominated the landscape. In the oceans, strange new sharks appeared. Giant insects walked amongst the trees while the first reptiles and early ancestors of what would become mammals hid inside rotted stumps.
Here are a couple of videos on how chickens make their eggs.
Here’s a video about how bird babies get air while they’re still inside the egg.
Here’s an article about the first known reptile.
Here’s an article about finding tiny fossils inside carboniferous tree stumps.
Here’s an article about an early ancestor of what one day would become the mammals.