Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ ɪ. iː z /; from Greek χονδρ- chondr-'cartilage', ἰχθύς ichthys 'fish') is a class that contains the cartilaginous fishes: they are jawed vertebrates with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone.
The discovery of an articulated 'conodont animal' in the Carboniferous rocks of Scotland and in the Ordovician of South Africa supports their current classification as an extinct group (Class Conodonta) of craniates, which includes jawless fish through to jawed vertebrates in the Phylum Chordata.
A vertebrate is a type of animal that has a series of nerves running from the brain down its back, covered by a special series of bones. These bones, called vertebrae, compose the spine and both protect the nerves and allow the animal a unique range of motion compared to less-evolved species.
Many placoderms, particularly the Rhenanida, Petalichthyida, Phyllolepida, and Antiarchi, were bottom-dwellers. As such, Placodermi has been popularly misinterpreted as being a tribe of bottom-feeding snails and garbage trucks, nevermind that the placoderms were the dominant vertebrate group during the Devonian.
In vertebrates the notochord is modified to form a cartilagenous or bonny vertebral column (a vertical structure made of series of units,vertebrae). This cartilagenous vertebral column is a characteristic of the Chondrichthyes like sharks. So sharks are vertebrates.
Stingrays are typically found in temperate waters. As of 2014, stingrays are considered to be a threatened species. Stingrays may reach a length of 6.5 feet and can weigh almost 800 pounds. These fish are related to sharks, another type of vertebrate, and have the same electrical sensors to help them locate prey.