Question

Which one of the followings is not a characteristic feature of mammals?

• A. Diphyodont tooth
• B. Ten pairs of cranial nerves
• C. Seven cervical vertebrae
• D. Left aortic arch in the circulatory system

Answer 1

The correct option is B Ten pairs of cranial nerves

Mammals have diphyodont teeth meaning two sets of teeth. The first set is called deciduous set and consecutively the second set is called permanent set. There are 33 vertebrae in mammals, namely 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 sacral vertebrae and 4 coccygeal vertebrae. There are 12 pairs of cranial nerves that arise directly from the brain in mammals. Left aortic arch is formed in the circulatory system by the fourth aortic arch and the left dorsal aorta.

Thus, the correct answer is 'Ten pairs of cranial nerves'.