They posses the following traits: vertebrae, bony skeleton, four limbs, and amniotic eggs
Phylogenetic trees present common traits to animals in similar phylums.
These trees characterize traits by having the animal ABOVE the trait. Take these few examples from here: primates and rodents and rabbits are the ONLY ones with hair and crocodiles and birds are the ONLY ones with eggs with shells.
Now that you know this, look at the 4 types of animals that must have the similar traits. Look for the characteristics that are below them. They are all above the following: vertebrae, bony skeleton, four limbs, and amniotic eggs. These are the traits that all the organisms similarly have.
For a better understanding, any animals BELOW the traits do NOT have the traits, take for example that sharks and ray-finned fish are below four limbs, meaning they don’t not possess this trait.
The process of organ formation in an embryo is called "Organogenesis." Organogenesis happens as early as week 5. It refers to the period after an egg has been fertilized and has been implanted in the uterus. The embryo develops the organs.