Which one among the following animals is not a mammal?

The question asks to identify the animal that is a mammal among the given options. The Great Indian Bustard is explicitly classified as a bird, specifically one of the heaviest terrestrial birds in the world [3]. The Hornbill is also categorized as a bird [2]. The Gharial (Gavialis gangeticus) is a member of the crocodilian family and is classified as a reptile [2]. In contrast, the Platypus (Ornithorhynchus anatinus) is a unique mammal belonging to the order Monotremata. Although it is an egg-laying animal, it possesses mammalian characteristics such as mammary glands and fur, distinguishing it from birds and reptiles [1]. Therefore, while the Bustard, Hornbill, and Gharial belong to the classes Aves and Reptilia respectively, the Platypus is the only mammal in the list.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Birds > p. 82
2. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 2: PLANT AND ANIMAL KINGDOMS > Table 2.1 (Contd.) > p. 14
3. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 4: BIODIVERSITY > IndIA – A MegA-BIodIversIty nAtIon. > p. 22