Question

Petromyzon belongs to class
A. Osteichthyes
B. Chondrichthyes
C. Cyclostomata
D. Amphibia

Answer 1

Hint: The petromyzon is a chordate and the common name of the Petromyzon is sea lamprey, it is sometimes called vampire fish because they have suctorial circular mouths.

Complete answer:
The common name of Petromyzon is sea lamprey. They have round and elongated eel-like bodies with soft and smooth skin, they do not have scales in their body. Petromyzon has a sectorial circular mouth with a single nostril that is single and median. Exoskeleton is not found in them and the endoskeleton is made up of cartilage with no bones. They do not have paired fins or paired appendages. Ten pairs of cranial nerves are present in them with a visible brain. As we mentioned, they are chordates so the notochord is present throughout their lives. They are unisexual so sex are separate.

They have five to sixteen in pairs of gills for respiration and the digestive system is present without a stomach. The heart is two chambered with a close circulation. They have lateral lines which act as a sense organ and excretory system made up of a pair of mesonephric kidneys. All these features of Petromyzon show that they belong to the class cyclostomes.

Hence, the correct answer is option (C).

Additional information:
The scientific classification of petromyzon is:
Kingdom: Animalia
Phylum: Chordata
Class: Cyclostomata
Order: Petromyzontiformes
Family: Petromyzontidae
Genus: Petromyzon

Note: In the cyclostomata, all the members have circular mouths by which they suck their food. Due to this circular mouth, they are called cyclostomata. As they suck their food, they are also known as vampire fish.