The correct answers are "bones in mammals" and "calcium-rich plates in echinoderms"
Explanation:
Endoskeletons are defined as internal structures of animals that give support to the body and are generally comprised of a mineralized tissue. Two examples of endoskeleton are the bones in mammals and the calcium-rich plates in echinoderms. The bones in mammals and other vertebrates are internal structures made of mineralized collagen, while the calcium-rich plates in echinoderms are internal structures that are interconnected and covered for an epidermis organ.
