Which feature distinguishes snakes from mammals?

The feature that distinguishes snakes from mammals is the presence of scales. Snakes, being reptiles, are covered in scales, which are made of keratin, a protein also found in human hair and nails. These scales play a crucial role in protecting the snake from environmental elements and help reduce water loss in their often dry habitats.

In contrast, mammals have fur or hair, which serves different functions, including insulation and sensory perception. This distinction in outer skin covering highlights a fundamental difference in the evolutionary adaptations of these two classes of animals.

The other features listed do not effectively differentiate snakes from mammals. Body temperature regulation varies between the two groups; while mammals are endothermic and can regulate their temperature internally, snakes are ectothermic, relying on external temperatures to regulate their body heat. Both snakes and mammals can reproduce on land, and while mammals also breathe air, this characteristic does not uniquely distinguish them from snakes, as snakes are also air-breathing creatures. Thus, the presence of scales is the definitive trait that sets snakes apart from mammals.