Question

Which of the following classes is incorrectly matched with its general characters?
A. Cyclostomata: Lack jaws and paired fins and body is covered with placoid scales
B. Osteichthyes: four pairs of gills are covered with an operculum and skin is covered with cycloid scales
C. Reptilia: Tympanum represents ear and fertilisation is internal
D. Aves: Endoskeleton is fully ossified and long bones are hollow with air cavities called pneumatic bones.

Answer 1

Hint: Class Cyclostomata is considered as the only living vertebrae as they lack true jaws and termed as Agnatha. Cyclostomata habitation includes marine or fresh-water vertebrates.

Complete answer:
Class Cyclostomata includes jawless vertebrae; their body is elongated and divided into two parts; trunk and tail. Paired fins and scales are not present. Sexual reproduction and external fertilization occur.

Class Osteichthyes involves all bony fishes with gills covered by an operculum which allows fish to breathe without swimming. They have jaws with teeth, dermal scales and paired fins are also present.

Class Reptilia includes burrowing terrestrial animals having scales on their body. A body having distinct parts; head, neck, trunk, and tail. All reptiles have fully-developed ears (exception snakes). Fertilization is internal.

Class Aves involves all the birds. Their endoskeleton is bony and long hollow bones are filled with air cavities defined as pneumatic bones. All birds are known to be oviparous and show sexual dimorphism in nature.

Hence, the correct answer is option (A).

Note: Some of the examples of Class Cyclostomata involve; eel, hagfish, lamprey, etc. Cyclostomes are primitive vertebrates. They lack jaws, paired fins, and dermal scales. Cyclostomes persist notochord throughout their life.