In older classifications, a superclass containing the four classes of fish: the two extant classes Chondrichthyes (cartilaginous fish, e.g. sharks) and Osteichthyes (bony fish), the extinct class Placodermi, and also the most primitive of the vertebrates of the class Cephalaspidomorphi. The first protofish are known from late Cambrian fossils, and the first true fish, an agnathan, has been recorded from earliest Ordovician sediments. Most modern classifications omit the term ‘Pisces’, regarding it as artificial. See also Gnathostomata.
Subjects: Zoology and Animal Sciences.