The endoskeleton is entirely cartilaginous in

The endoskeleton is entirely cartilaginous in Chondrichthyes, e.g., Pristis (sawfish). The endoskeleton in Osteichthyes (e.g., Pterophyllum) is chiefly bony. The endoskeleton is fully ossified in Aves (e.g., Psittacula). The endoskeleton of mammals (e.g., Pteropus) is mainly made up of bone and contains some cartilage also.