1.

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

Answer»
Living jawless fishesCartilaginous fishes
1. These belong to class cyclostomata under subphylum vertebrata, phylum chordataThese 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 teethTeeth are modified placoid scales which are backwardly directed.
5. They have pouch like gills.They have lamelliform gills without operculum
Eg: Petromyzon, lampreyEg: Trygon (stingray)



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