The most primitive type of mammalian placenta is

Options

A. Syndesmochorial
B. Endotheliochorial
C. Haemochorial
D. Epitheliochorial.

Answer

**Step-by-Step Solution:**

1. **Understanding Placenta Types**: The question asks for the most primitive type of mammalian placenta. To answer this, we need to understand the different types of placentation in mammals.

2. **Identifying the Options**: The options provided are:
- A) Syndesmocorial
- B) Endotheliochorial
- C) Hemocorial
- D) Epitheliochorial

3. **Analyzing Each Type**:
- **Endotheliochorial**: In this type, the chorionic villi are in contact with the endothelium of maternal blood vessels. This type is found in most carnivores, such as cats and dogs, but it is not the most primitive type.
- **Epitheliochorial**: This type involves the chorionic villi growing into the uterine epithelium. It is found in most ruminants, such as horses and whales, and is considered the most primitive type of placentation.
- **Hemocorial**: In hemocorial placentation, maternal blood comes into direct contact with the fetal chorion. While this is a significant type, it is not the most primitive.
- **Syndesmocorial**: This type involves the chorion coming into direct contact with the connective tissue of the uterus, but it is also not the primitive type.

4. **Conclusion**: After analyzing all the options, the most primitive type of mammalian placenta is **Epitheliochorial** (Option D).

5. **Final Answer**: The correct answer is **D) Epitheliochorial**.

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