Question

How many fish types are there?

Answer 1

Fish:

Fish are aquatic vertebrate animals of class Chordata that have gills but lack limbs fingers or toes.

Classification of fish:

1. Class Agnatha (jawless fish)
   1. Jawless mouth - suctorial or filter-feeding mouth
   2. Lack paired fins
   3. Lack internal skeleton system
2. Class Chondrichthyes (cartilaginous fish)
   1. Lacks true bone - cartilaginous endoskeleton
   2. Skin is covered by small tooth-like structures called placoid scales
   3. Teeth are are not attached to jawbones.
   4. eg: Sharks, Skates, and Rays
3. Class Osteichthyes (bony fish)
   1. Bony endoskeleton
   2. Skins are protected by protective scales.
   3. Airbladder present under the skeleton to allow them to remain buoyant.

Other classes that are currently extinct:

1. Class Placodermi (armoured fish)
2. Class Acanthodii (spiny sharks)