Well, an endoskeleton is an internal skeleton, like humans have.
Pro: Bones do not get broke as easily, since they are inside of the body. Bones that break also heal more quickly in an endoskeleton, since they have tissue and blood surrounding it and transferring nutrients.
Con: The flesh can get easily damaged. There is no shedding with endoskeletons, so a new skeleton cannot be grown in the event of an injury.
Embryo retention, a cuticle, stomata, and vascular tissue. Hope this helps!
Collagen has definetly a lot more of protein. Collagen is also one of the most used protein in the animal kingdom!
