Simplify the following text for a Grade 12 native English-speaking person.
Original: Chondrichthyes ( ; from Greek Ï Î Î 1\/2 Î Ï - chondr - ` cartilage ' , á 1\/4 Ï Î Ï Ï ichthys ` fish ' ) or cartilaginous fishes are jawed fish with paired fins , paired nares , scales , two-chambered hearts , and skeletons made of cartilage rather than bone .
Simplified: Chondrichthyes or cartilaginous fishes are jawed fish with paired fins , paires nostrils , scales , two-chambered hearts , and skeletons made of cartilage rather than bone .