Which of the following dental formulae represents the dentition in rabbits?

Analyze the question: You need the dental formula of a rabbit. A dental formula shows, for one side of the mouth, the number of incisors (I), canines (C), premolars (P) and molars (M), with the upper jaw on top and the lower jaw below.

Concept: Rabbits are lagomorphs, and their dentition is adapted for gnawing and grinding plant material:

• They have two pairs of upper incisors. One large pair is at the front, with a small peg-like pair right behind it. They have one pair of lower incisors.
• They have no canines. A gap called the diastema lies where the canines would be.
• They have 3 upper and 2 lower premolars on each side.
• They have 3 upper and 3 lower molars on each side.

Solution:

Rabbit dental formula (one side):

I 2/1, C 0/0, P 3/2, M 3/3

Total teeth = 2 × (3 + 0 + 5 + 6) = 2 × 14 = 28 teeth.

Checking the options:

• A. I 2/1, C 0/0, P 3/2, M 3/3. This matches.
• B. It has canines, which rabbits lack, and it looks more like a carnivore or omnivore pattern. Wrong.
• C. The incisors are 1/2 and the premolars 2/3, which is the wrong way round. Wrong.
• D. It has a lower canine (0/1), which rabbits do not have. Wrong.

Answer: A

Exam tip: Remember "rabbits have 28 teeth, no canines, and a diastema." Option A is the only one with C 0/0 and the 2/1 incisor pattern. The "2 over 1" incisors are the key rabbit feature, because the extra small upper pair is what separates rabbits from rodents, which have 1/1.