Which is not a trait of prototherians

Options

A. Ovipary
B. Lack of teeth
C. Absence of corpus callosum
D. Extra-abdominal testes .

Answer

To determine which trait is not characteristic of prototherians, let's analyze each option step by step:

1. **Ovipary**: Prototherians are known as egg-laying mammals. They reproduce by laying eggs, which is a defining trait of this group. Therefore, this statement is true regarding prototherians.

2. **Lack of Teeth**: Many prototherians, such as the platypus, do not have teeth in the traditional sense. Instead, they have a beak-like structure. This trait is also true for prototherians.

3. **Absence of Corpus Callosum**: The corpus callosum is a structure that connects the left and right hemispheres of the brain and is found in placental mammals. Prototherians, however, do not possess a corpus callosum. This statement is also true for prototherians.

4. **Extra Abdominal Testis**: This trait refers to the presence of testes located outside the abdominal cavity, which is typical in many mammals, particularly in placental mammals. Prototherians do not exhibit this trait, as their reproductive anatomy is different.

Based on the analysis above, the statement that is **not a trait of prototherians** is **extra abdominal testis**. Therefore, the correct answer is option number four.

### Summary of the Solution:
- Ovipary: True for prototherians.
- Lack of teeth: True for prototherians.
- Absence of corpus callosum: True for prototherians.
- Extra abdominal testis: **Not true for prototherians**.

### Final Answer:
**Extra abdominal testis** is not a trait of prototherians.

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