Question

List the characteristic features that distinguish cartilaginous fishes with living jawless fishes. 

Answer 1

Living jawless fishes	Cartilaginous fishes
1. These belong to class cyclostomata under subphylum vertebrata, phylum chordata	These belong to class Chondrichthyes under subphylum Vertebrata, phylum chordata
2. These are jawless fishes. 3. Mouth is circular and suctorial.	Mouth is located ventrally and Jaws are very powerful.
4. They have true teeth	Teeth are modified placoid scales which are backwardly directed.
5. They have pouch like gills.	They have lamelliform gills without operculum
Eg: Petromyzon, lamprey	Eg: Trygon (stingray)