Q. From which features do osteichthyes and condrichthyes get these names?
"Chondros" means cartilage, "ictis" means fish (both from the Greek) the name chondrichtians is for fishes with cartilaginous endoskeleton. The name osteichthyes comes from the existence of a bony endoskeleton in these fishes ("osteo" means bone, from the Greek too).